Roof Repair Terms



American Architectural Manufacturers Association

Abrasion Resistance

the ability to resist being worn away by contact with another moving, abrasive surface, such as foot traffic, mechanical equipment, wind-blown particles, etc.


the ability of a material to accept within its body, quantities of gases or liquid, such as moisture.

Accelerated Weathering

the exposure of a specimen to a specified test environment for a specified time with the intent of producing in a shorter time period, effects similar to actual weathering.


American Concrete Institute

Acid etch

in waterproofing, the use of a strong acid to remove the surface of concrete to expose the aggregate.


American Council of Independent Laboratories

Acrylic coating

a liquid coating system based on an acrylic resin. Generally, a latex-based coating system that cures by air drying.

Acrylic resin

polymers of acrylic or methacrylic monomers. Often used as a latex base for coating systems.

Active metal (anodic)

a metal or material that readily gives up electrons to a cathodic (noble) material. (See anodic). An active metal will corrode in the presence of moisture when in contact with a cathodic metal.


to cause two surfaces to be held together by adhesion, typically with asphalt or roofing cements in built-up roofing and with contact cements in some single-ply membranes.


steady or firm attachment.

Adhesive bond break

a material to facilitate independent movement between two units that would otherwise bond together.


American Fiberboard Association


Associated General Contractors of America

Aged R-value

thermal resistance value established by utilizing artificial conditioning procedures for a prescribed time period.


(1) crushed stone, crushed slag or water-worn gravel used for surfacing a built-up roof system; (2) any grandular material.


the effect on materials that are exposed to an environment for an interval of time.


American Hardboard Association


American Institute of Architects

Air Leakage

the unintended movement of air from a location where it is intended to be contained to another location.


the cracking of the surfacing bitumen on a bituminous roof or coating on a SPF roof, producing a pattern of cracks similar to an alligator's hide; the cracks may not extend completely through the surfacing bitumen or coating.

Aluminized Steel

sheet steel with a thin aluminum coating bonded to the surface to enhance weathering characteristics.


a nonrusting, malleable metal sometimes used for metal roofing and flashing.

Ambient Temperature

the temperature of the air; air temperature.


a metal or material that readily gives up electrons to a cathodic material in the presence of a electrolyte (see Galvanic series).


American National Standards Institute.

Anticapillary hem

a hem used in a metal panel seam to reduce the potential for water migration.


American Plywood Association


American Plastics Council.


American Plastics Council/Spray Polyurethane Foam Alliance.


see Atactic Polypropylene.

Application Rate

the average quantity (mass, volume, or thickness) of material applied per unit area.

Apron Flashing

a term used for a flashing located at the juncture of the top of the sloped roof and a vertical wall, chimney or steeper-sloped roof.

Architectural panel

a metal roof panel, typically a double standing seam or batten seam; usually requires solid decking underneath and relies on slope to shed water.

Architectural shingle

an asphalt shingle that provides a dimensional appearance.

Area divider

a raised, flashed assembly typically a single- or double-wood member attached to a wood base plate, that is anchored to the roof deck. It is used to accommodate thermal stresses in a roof system where an expansion joint is not required, or to separate large roof areas or separate roof systems comprised of different/incompatible materials, and may be used to facilitate installation of tapered insulation.

Area practices

design or application techniques peculiar to a specific geographical region.


Asphalt Roofing Manufacturers Association.


American Subcontractors Association


a group of natural, fibrous, impure silicate materials.


Associated Specialty Contractors


American Society of Home Inspectors


American Society of Heating, Refrigerating & Air-Conditioning Engineers, Inc.


a dark brown or black substance found in a natural state or, more commonly, left as a residue after evaporating or otherwise processing crude oil or petroleum. Asphalt may be further refined to conform to various roofing grade specifications: Dead-Level Asphalt: a roofing asphalt conforming to the requirements of ASTM Specification D 312, Type I. Flat Asphalt: a roofing asphalt conforming to the requirements of ASTM Specification D 312, Type II. Steep Asphalt: a roofing asphalt conforming to the requirements of ASTM Specification D 312, Type III. Special Steep Asphalt: a roofing asphalt conforming to the requirements of ASTM Specification D 312, Type IV.

Asphalt emulsion

a mixture of asphalt particles and an emulsifying agent, such as bentonite clay and water.

Asphalt felt

an asphalt-saturated and/or asphalt-coated felt (see Felt).

Asphalt primer

see Primer.

Asphalt roof cement

a trowelable mixture of solvent-based bitumen, mineral stabilizers, other fibers and/or fillers. Classified by ASTM Standard D 2822-91 Asphalt Roof Cement, and D 4586-92 Asphalt Roof Cement, Asbestos-Free, Types I and II. Type I is sometimes referred to as "plastic cement," and is made from asphalt characterized as self-sealing, adhesive and ductile, and conforming to ASTM Specification D 312, Type I; Specification D 449, Types I or II; or Specification D 946 (see Plastic cement and Flashing cement.) Type II is generally referred to as "vertical-grade flashing cement," and is made from asphalt characterized by a high softening point and relatively low ductility, and conforming to the requirement of ASTM Specification D 312, Types II or III; or Specification D 449, Type III. (see Plastic cement and Flashing cement.)

Asphalt shingle

a shingle manufactured by coating a reinforcing material (felt or fibrous glass mat) with asphalt and having mineral granules on the side exposed to the weather. (see Shingle)

Asphalt, Air blown

asphalt produced by blowing air through molten asphalt to raise its softening point and modify othr properties.


a high molecular weight hydrocarbon fraction precipitated from asphalt by a designated solvent (paraffinic naphtha) at a specified temperature and solvent-asphalt ratio.


American Society for Testing and Materials.

Atactic polypropylene

a group of high molecular weight polymers formed by the polymerization of propylene.


the cavity or open space above the ceiling and immediately under the roof deck of a steep-sloped roof.


American Wood Preservatives Association


American Welding Society

Back-nailing (also referred to as "Blind-nailing")

the practice of blind nailing the back portion of a roofing ply, steep roofing unit, or other components in a manner so that the fasteners are covered by the next sequential ply, or course, and are not exposed to the weather in the finished roof system.


fine mineral matter applied to the back side of asphalt shingles and roll roofing to keep them from sticking together while packaged.


a material, such as aggregate or precast concrete pavers, which employs its mass and the force of gravity to hold (or assist in holding) single-ply roof membranes in place.

Bar joist

(see Steel joist).

Barrel vault

a building profile featuring a rounded profile to the roof on the short axis, but with no angle change on a cut along the long axis.

Barrier board

noncombustible board stock material of low thermal conductivity placed between two elements of a roof assembly.

Base flashing (membrane base flashing)

plies or strips of roof membrane material used to close-off and/or seal a roof at the horizontal-to-vertical intersections, such as at a roof-to-wall juncture. Membrane base flashing covers the edge of the field membrane. (see Flashing.)

Base ply

the bottom or first ply in a built-up roof membrane when additional plies are to be subsequently installed.

Base sheet

an impregnated, saturated, or coated felt placed as the first ply in some low-slope roof systems.


(1) cap or cover; (2) in a metal roof, a metal closure set over, or covering the joint between, adjacent metal panels; (3) in a wood, a strip of wood usually set in or over the structural deck, used to elevate and/or attach a primary roof covering such as tile; (4) in a single ply membrane roof system, a narrow plastic, wood, or metal bar which is used to fasten or hold the roof membrane and/or base flashing in place.

Batten seam

a metal panel profile attached to and formed around a beveled wood or metal batten.

Beaufort Scale

a scale in which the force of the wind is indicated on a scale of 0 to 12, as follows


a porous clay formed by the decomposition of volcanic ash that swells 5 to 6 times its original volume in the presence of water.

Bermuda seam

a metal panel profile featuring a step-down profile that runs perpendicular to the slope of the roof.

Bi-Level Drain

see Dual-Level Drain.

Bird bath

random, inconsequential amounts of residual water on a roof membrane.

Bird Screen

wire mesh used to prevent birds from entering the building through ventilators, louvers, or other openings. (See Insect Screen.)


(1) a class of amorphous, black or dark colored, (solid, semi-solid, or viscous) cementitious substances, natural or manufactured, composed principally of high molecular weight hydrocarbons, soluble in carbon disulfide, and found in petroleum asphalts, coal tars, pitches and asphaltenes; (2) a generic term used to denote any material composed principally of bitumen, typically asphalt or coal tar.


see Envelope and Bleed Sheet.

Bituminous emulsion

a suspension of minute particles of bituminous material in water.

Blackberry (also referred to as "Blueberry" or "Tar-boil")

a small bubble or blister in the flood coat of an aggregate-surfaced built-up roof membrane.

Blanket (batt) insulation

glass fiber or other compressible fibrous insulation, generally available in roll form.


a sheet material used to prevent the migration of bitumen.

Bleeder strip

(see Rake-Starter).


the use of nails that are not exposed to the weather in the finished roofing system.


an enclosed pocket of air, which may be mixed with water or solvent vapor, trapped between impermeable layers of felt or membrane, or between the membrane and substrate.


sections of wood (which may be preservative treated) built into a roof assembly, usually attached above the deck and below the membrane or flashing, used to stiffen the deck around an opening, act as a stop for insulation, support a curb, or serve as a nailer for attachment of the membrane and/or flashing.

Blowing agent

an expanding agent used to produce a gas by chemical or thermal action, or both, in manufacture of hollow or cellular materials.


Building Officials and Code Administrators, International, Inc. (author of "The BOCA National Building Code").


Building Owners & Managers Association, International


the adhesive and/or cohesive forces holding two components in positive contact.

Bond, Chemical

adhesion between surfaces, usually of similar materials, resulting from a chemical reaction or cross-linking of polymer chains.

Bond, Mechanical

adhesion between surfaces resulting from interfacial forces or a physical interlocking.

Bonding Agent

a chemical substance applied to a suitable substrate to create bond between it and a succeeding layer.


(1) a covering made of flexible material, which may be preformed to a particular shape, used to exclude dust, dirt, moisture, etc., from around a penetration; (2) a flexible material used to form a closure, sometimes installed at inside and outside corners.


hand- or power-activated machinery used to bend metal.


(1) when membrane or base flashing is unsupported at a juncture; (2) bridging in steep-slope roofing occurs when reroofing over standard-sized asphalt shingles with metric-sized asphalt shingles.

British thermal unit (BTU)

the heat energy required to raise the temperature of 1 pound of water one degree Fahrenheit (joule). For the metric equivalent, see Joule.


uniformly cast or distribute grandular or aggregate surfacing material.


to improve the embedding of a ply or membrane by using a broom or squeegee to smooth it out and ensure contact with the adhesive under the ply or membrane.


an upward, elongated displacement of a roof membrane frequently occurring over insulation or deck joints. A buckle may be an indication of movement within the roof assembly.

Building code

the minimum construction requirements established generally by national organizations of experts and adopted completely or in altered form by local governing authorities.

Built-up roof (BUR)

a continuous, semi-flexible roof membrane, consisting of multiple plies of saturated felts, coated felts, fabrics or mats assembled in place with alternate layers of bitumen, and surfaced with mineral aggregate, bituminous materials, a liquid-applied coating or a granule-surfaced cap sheet.

Bun stock

large solid box-like structure formed during the production of polystyrene insulation; individual board stock pieces are then cut from the bun.


an individual package of shakes or shingles.

Bush Hammer

a hammer, originally a hand tool but now usually power driven, having a serrated face containing many pyramid-shaped points; used to provide a roughened surface on concrete.

Butt joint

a joint formed by adjacent, separate sections of material, such as where two neighboring pieces of insulation abut.

Button punch

a process of indenting two or more thicknesses of metal that are pressed against each other to prevent slippage between the metal.


rubber-like material produced by polymerizing isobutylene.

Butyl coating

an elastomeric coating system derived from polymerized isobutylene. Butyl coatings are characterized by low water vapor permeability.

Butyl rubber

a synthetic elastomer based on isobutylene and a minor amount of isoprene. It can be vulcanizable and features low permeability to gases and water vapor.

Butyl tape

a sealant tape sometimes used between metal roof panel seams and/or end laps; also used to seal other types of sheet metal joints, and in various sealant applications.


a structural framing member.


Council of American Building Officials


(1) to press between rollers or plates in order to smooth and glaze or to thin into sheets; (2) a machine for calendering.


a manufacturing process by which some polymeric membranes and other sheetings are produced.


a slight convexity, arching or curvature (as of a beam, roof deck or road).


any overhanging or projecting roof structure, typically over entrances or doors.


in SPF-based roofing, a beveling of foam at horizontal/vertical joints to increase strength and promote water run off.

Cant strip

a beveled strip used under flashings to modify the angle at the point where the roofing or waterproofing membrane meets any vertical element.

Cap flashing

(1) usually composed of metal, used to cover or shield the upper edges of the membrane base flashing wall flashing; (2) a flashing used to cover the top of various buildings components, such as parapets or columns. (see Flashing and Coping.)

Cap sheet

a sheet, often granule-surfaced, used as the top ply of some built-up or modified bitumen roof membranes and/or flashings.

Capacitance meter

a device used to locate moisture or wet materials within a roof system by measuring the ratio of the change to the potential difference between two conducting elements separated by a non-conductor.

Capillary action

(1) the action by which the surface of a liquid where it is in contact with a solid is elevated or depressed depending on the relative attraction of the molecules of the liquid for each other and for those of the solid; (2) the siphoning of liquid into a joint or void between two adjacent surfaces.


an ingredient that initiates a chemical reaction or increases the raate of a chemical reaction when combined with another chemical.


a metal or material that readily attracts electrons from an anodic material in the presence of an electrolyte (see Galvanic Series).


a composition of vehicle and pigment used at ambient temperatures for filling/sealing joints or junctures, that remains elastic for an extended period of time after application.


(1) the physical process of sealing a joint or juncture; (2) sealing and making weather-tight the joints, seams, or voids between adjacent surfaces by filling with a sealant.


the formation of a partial vacuum or cavity in a liquid.

Cavity wall

an exterior wall usually of masonry, consisting of an outer and inner withe separated by a continuous air space, but connected together by wire or sheet-metal tiles.


100 cubic feet.

Cellular glass insulation

a rigid closed-cell insulation board made from crushed glass and hydrogen sulfide gas.

Cementitious waterproofing

heavy cement-based compounds and various additives that are mixed and packaged for use in a dry form; the packaged mixture is then mixed with water and liquid bonding agents to a workable concrete-like consistency.


a unit of measure of absolute viscosity. (The viscosity of water is one centipoise. The lower the number, the less viscous the material.)


a unit of viscosity; the ratio of a liquid's absolute viscosity to the density of that liquid.


Construction Engineering Research Laboratory.


a powdery residue on the surface of a material.

Chalk line

a line made on the roof or other flat surface by snapping a taut string or cord dusted with colored chalk.


the formation of a powdery surface condition from the disintegration of a binder or elastomer.

Channel flashing

in steep-slope roof construction, a type of flashing used at roof-to-wall junctures and other roof-to-vertical plan intersections where an internal gutter is needed to handle runoff. Commonly used with profile tile.

Chemical resistance

the ability to withstand contact with specified chemicals without a significant change in properties.


a style of metal panel seaming/design.


stone, masonry, prefabricated metal, or a wood framed structure, containing one or more flues, projecting through and above the roof.

Chlorinated polyethylene (CPE)

a thermoplastic material, used for single-ply roof membranes, composed of high molecular weight polyethylene which has been chlorinated with a process that yields a flexible rubber-like material.

Chlorosulfonated polyethylene (CSPE or CSM)

probably best known by the DuPont trade name HypalonTM), a synthetic, rubber-like thermoset material, based on high molecular weight polyethylene with suphonyl chloride, usually formulated to produce a self-vulcanizing membrane. Classified by ASTM Standard D 5019.


a material used as the exterior wall enclosure of a building.


a continuous metal strip, or angled piece, used to secure metal components (also see Clip).


an upward extension of enclosed space created by carrying a setback vertical, wall (typically glazed) up and through the roof slope. Two intersecting shed roofs on different planes.


a non-continuous metal component or angle piece used to secure two or more metal components together. (see Cleat.)

Clipped gable

a gable cutback near the peak in a hip-roof form.

Closed-cut valley

a method of valley application in which shingles from one side of the valley extend across the valley while shingles from the other side are trimmed back approximately 2 inches (51 mm) from the valley centerline.

Closure strip

a metal or resilient strip, such as neoprene foam, used to close openings created by joining metal panels or sheets and flashings.

Coal tar

a dark brown to black colored, semi-solid hydrocarbon produced by the distillation of coal. Coal tar pitch is further refined to conform to the following roofing grade specifications:

Coal tar bitumen

a proprietary trade name for Type III coal tar used as the dampproofing or waterproofing agent in dead-level or low-slope built-up roof membranes and membrane waterproofing systems, conforming to ASTM D 450, Type III.

Coal tar felt

a felt that has been saturated or impregnated with refined coal tar.

Coal tar pitch

a coal tar used as the waterproofing agent in dead-level or low-slope built-up roof membranes and membrane waterproofing systems, conforming to ASTM Specification D 450, Type I.

Coal tar roof cement

a trowelable mixture of processed coal tar base, solvents, mineral fillers and/or fibers. Classified by ASTM Standard D 4022, "Coal Tar Roof Cement, Asbestos Container."

Coal tar waterproofing pitch

a coal tar used as the dampproofing or waterproofing agent in below-grade structures, conforming to ASTM Specification D 450, Type II.

Coarse orange peel surface texture

a surface showing a texture where nodules and valleys are approximately the same size and shape. This surface is acceptable for receiving a protective coating because of the roundness of the nodules and valleys.

Coated base sheet

a coated felt intended to be used as a base ply in a built-up or modified bitumen roof membrane.

Coated fabric

fabrics that have been impregnated and/or coated with a plastic like material in the form of a solution, dispersion hot-melt or powder. The term also applies to materials resulting from the application of a preformed film to a fabric by means of calendering.

Coated felt (Sheet)

(1) an asphalt felt that has been coated on both sides with harder, more viscous asphalt; (2) a glass fiber felt that has been simultaneously impregnated and coated with asphalt on both sides.


a layer of liquid material applied to a surface for protection or appearance.


a phenomenon observed during spray application characterized by the formation of web-like threads along with the usual droplets leaving the spray gun nozzle.


a collection of laws (regulations, ordinances or statutory requirements) adopted by governmental authority. (see Building code and Model code.)

Coefficient of thermal expansion

the coefficient of change in dimension of a material per unit of dimension per degree change in temperature.


the molecular forces of attraction by which the body of a material is held together.

Coil coating

the application of a finish to a coil of metal using a continuous mechanical coating process.

Cold Flow

relatively slow deformation of a material at or below room temperature. (See Creep).

Cold forming

the process of shaping metal into desired profiles without the application of heat.

Cold Process Built-Up Roof

a continuous, semi-flexible roof membrane, consisting of a ply or plies of felts, mats or other reinforcement fabrics that are laminated together with alternate layers of liquid-applied (usually asphalt-solvent based) roof cements or adhesives installed at ambient or a slightly elevated temperature.

Cold rolled

the process of forming steel into sheets, panels, or shapes on a series of rollers at room temperature.

Cold roof assembly

a roof assembly configured with the insulation below the deck, not typically in contact with the deck, allowing for a ventilation space. The temperature of the roof assembly remains close to the outside air temperature.

Collector Box

see Conductor Head.

Color stability

the ability of a material to retain its original color after exposure to weather.


in structures, a relatively long, slender structural compression member such as a post, pillar or strut; usually vertical which acts in (or near) the direction of its longitudinal axis.

Combing ridge

a term used to describe an installation of finishing slate or wood at the ridge of a roof whereby the slates on one side project beyond to the apex of the ridge.


capable of burning.


a chemical process of oxidation that occurs at a rate fast enough to produce heat and usually light either as glow or flames; the process of burning.

Compatible materials

two or more substances that can be mixed, blended, or attached without separating, reacting, or affecting the materials adversely.

Composite board roof insulation

rigid board insulation generally comprised of perlite or wood fiberboard factory bonded to polyisocyanurate or polystyrene.

Composition shingle

a unit of asphalt shingle roofing.

Compounded thermoplastics

a category of roofing membranes made by blending thermoplastic resins with plasticizers, various modifiers, stabilizers, flame retardants, UV absorbers, fungicides, and other proprietary substances, alloyed with proprietary organic polymers.

Compressive strength

the property of a material that relates to its ability to resist compression loads.

Concealed plate

see Cover plate.

Concealed-nail method

a method roofing application in which all nails are driven into the underlying course of roofing and covered by a subsequent, overlapping course.


the liquid resulting from the condensation of a gas.


the conversion of water vapor or other gas to liquid phase as the temperature drops; the act or process of condensing.


to make denser or more compact, as when a material (e.g., water vapor) changes from its gas phase to its liquid phase.


the storage of a material specimen under specified temperature, humidity, etc. for a specified time prior to testing.

Conductance, Thermal

the thermal transmission in unit time through unit area of a particular body or assembly having defined surfaces, when unit average temperature difference is established between the surfaces. C=Btu/h.ft2.F (C=W/m2.K).

Conductor head

an enlargement or catch basin at the top of a downspout or leader to receive rainwater from a gutter or scupper.

Construction joint

(1) a joint where two successive placements of concrete meet; (2) a separation provided in a building which allows its component parts to move with respect to each other.

Contact cements

adhesives used to adhere or bond various roofing components. These adhesives adhere mated components immediately on contact of surfaces to which the adhesive has been applied.


the process of making a material or surface unclean or unsuited for its intended purpose, usually by the addition or attachment of undesirable foreign substances.

Control joint

a groove which is formed, sawed, or tooled in a concrete or masonry structure to regulate the location and amount of cracking and separation resulting from the dimensional change or different parts of the structure, thereby avoiding the development of high stresses.


the covering piece on top of a wall exposed to the weather, usually made of metal, masonry, or stone and sloped to carry off water.


the product of polymerization of two or more substances (as two different isomers) together.


a chemical reaction that results in the bonding of two or more dissimilar monomers to produce large, long-chain molecules that are copolymers.


a natural weathering metal used in metal roofing or flashing; typically used in 16 ounce per square foot (0.56 mm) and 20 ounce per square foot (0.69 mm) thicknesses.

Core cut or core sample

(1) a sample from a low-slope roof system taken for the purpose of obtaining primarily qualitative information about its construction. Typically, core cut analysis can verify or reveal the type of membrane surfacing; the type of membrane; the approximate number of plies; the type, thickness and condition of the insulation (if any); and the type of deck used as a substrate for the roof system. (2) for in SPF-based roof systems, core cuts are used to obtain both quantitative and qualitative information, such as the thickness of the foam, the thickness and adhesion of the coating, thickness of individual passes and adhesion between passes and the adhesion of the foam to its substrate.


the decorative horizontal molding or projected roof overhang.

Counter batten

vertical wood strips installed on sloped roofs over which horizontal battens are secured. The primary roof covering is attached or secured to these horizontal battens.


formed metal or elastomeric sheeting secured on or into a wall, curb, pipe, rooftop unit or other surface, to cover and protect the upper edge of a base flashing and its associated fasteners.


(1) the term used for a row of roofing material that forms the roofing, waterproofing or flashing system; (2) one layer of a series of materials applied to a surface (e.g., a five-course wall flashing is composed of three applications of roof cement with one ply of felt or fabric sandwiched between two layers of roof cement).


see Fillet.

Cover board

an insulation board used over closed cell plastic foam insulation (e.g., polyisocyanurate) to prevent blistering when used in conjunction with hot bituminous membranes. Suitable cover board insulation are glass-faced siliconized gypsum board, glass-fiber board, perlite board, wood-fiber board of mineral-fiber board. Cover boards are also recommended between polyisocyanurate insulation and single ply membranes to protect the polyisocyanurate.

Cover plate

a metal strip sometimes installed over or under the joint between formed metal pieces.


the surface area uniformly covered by a specific quantity of a particular material at a specific thickness.


copolymer alloy.


Chlorinated Polyethylene.


a non-linear separation or fracture occurring in a material.

Cream time

time in seconds (at a given temperature) when the A and B components of polyurethane foam will begin to expand after being mixed. Recognizable as a change in color of the materials.


the permanent deformation of a roofing material or roof system caused by movement of the roof membrane, or compression of a roof insulation board at fastener positions, that results from continuous load or thermal stress or loading. Creep at roof temperature is sometimes called "cold flow."


a relatively small area of a roof constructed to divert water from a horizontal intersection of the roof with a chimney, wall, expansion joint or other projection. (see Saddle.)

Cross Ventilation

the effect that is provided when air moves through a roof cavity between the vents.


the formation of chemical bonds between polymeric chains. Cross-linking of rubber is referred to as vulcanizing or "curing."


Cold Regions Research and Engineering Laboratory.

Crystalline waterproofing

a compound of cement, quartz or silica sand, and other active chemicals that are mixed and packaged for use in a dry powder form; the packaged mixture is then mixed with water and applied to a concrete surface where it penetrates into the pores of concrete.


Construction Specifications Institute


ASTM designation for chlorosulfonated polyethylene. (See CSPE.)


chlorosulfonated polyethylene.


a relatively small roofed structure, generally set on the ridge or peak of a main roof area for ventilation or aesthetic purposes.


(1) a raised member used to support roof penetrations, such as skylights, mechanical equipment, hatches, etc. above the level of the roof surface; (2) a raised roof perimeter relatively low in height.


a process whereby a material is caused to form permanent molecular linkages by exposure to chemicals, heat, pressure, and/or weathering.

Cure time

the time required for a material to reach its desirable long-term physical characteristics.

Cured concrete

concrete that has attained its intended design performance properties.

Curing agent

an additive in a coating or adhesive that results in increased chemical activity between the components with an increase or decrease in rate of cure.

Curing compound

a liquid that is sprayed or otherwise applied to newly placed concrete which retards the loss of water during curing.


solvent-thinned bitumen used in cold-process roofing adhesives, roof cements and roof coatings.


a permanent detail designed to prevent lateral water movement in an insulation system and used to isolate sections of a roofing system. (Note: A cutoff is different from a tie-in, which may be a temporary or permanent seal.) (see Tie-In.)


the open portions of a strip shingle between the tabs. Sometimes referred to as a keyway.


treatment of a surface or structure to resist the passage of water in the absence of hydrostatic pressure.

Dead level

absolutely horizontal or zero slope. (see Slope.)

Dead loads

the weight of a structure itself, including the weight of fixtures or equipment permanently attached to it.

Dead-level asphalt

see Asphalt.


a structural component of the roof of a building. The deck must be capable of safely supporting the design dead and live loads, including the weight of the roof systems, and the additional live loads required by the governing building codes and provide the substrate to which the roofing or waterproofing system is applied the structural surface of a building to which a roof assembly is installed. Decks are either non-combustible (e.g., corrugated metal, concrete, or gypsum) or combustible (e.g., wood plank or plywood).

Deflection (bowing, sagging)

(1) the deformation of a structural member as a result of loads acting on it; (2) any displacement in a body from its static position, or from an established direction or plane, as a result of forces acting on the body.


a deleterious change in the chemical structure, physical properties or appearance of a material from natural or artifical exposure (e.g., exposure to radiation, moisture, heat, freezing, wind, ozone, oxygen, etc.)

Degree days

a unit used in estimating the fuel consumption for a building; equal to the number of degrees that the mean temperature, for a 24-hour day, is below the "base temperature"; the base temperature is taken as 65 degrees F (18.3 C) in the U.S.A.


separation of the laminated layers of a component or system.

Design loads

the total load on a structural system for the most severe combination of loads and forces which it is designed to sustain.

Dew-point temperature

the temperature at which air becomes saturated with water vapor. The temperature at which air has a relative humidity of 100%.


a floor slab, metal wall panel, roof panel, or the like, having a sufficiently large in-plane shear stiffness and sufficient strength to transmit horizontal forces to resisting systems.


the movement of water vapor from regions of high concentration (high water vapor pressure) toward regions of lower concentration.

Dimensional shingle

a shingle that is textured, overlayed, or laminated and designed to produce a three-dimensional effect. (also see Laminated shingle and Architectural shingles.)

Dimensional stability

the degree to which a material maintains its original dimensions when subjected to changes in temperature and humidity.


Department of Energy.


a roof that is shaped like a half-circle, or a variation of one.


a structure projecting from a sloping roof usually housing a window or ventilating louver.

Double coverage

application of asphalt, slate, or wood roofing such that the lapped portion is at least 2 inches (50 mm) wider than the exposed portion, resulting in two layers of roofing material over the deck.

Double Graveling

the process of applying two layers or flood coats of bitumen and aggregate to a built-up roof. Loose aggregate should be swept from the first application prior to the second coating of bitumen and aggregate. Approximately 50% of the second aggregate application will remain adhered in the bitumen flood coat unless physically removed.

Double lock standing seam

in a metal roof panel or metal cap, a standing seam that uses a double overlapping interlock between two metal panels. (see Standing seam.)

Double pour

to apply two layers or flood coats of bitumen and aggregate to a built-up roof.


a vertical pipe or conduit used to carry runoff water from a scupper, conductor head or gutter of a building to a lower roof level or to the ground or storm water runoff system.

Drag load

the external force (e.g., from the weight of ice and snow) applied to a steep-slope roof system component forcing the component downslope.


an outlet or other device used to collect and direct the flow of runoff water from a roof area.

Drip edge

a metal flashing or other overhanging component with an outward projecting lower edge, intended to control the direction of dripping water and help protect underlying building components.


free or relatively free from a liquid, especially water; (2) to remove water or moisture.

Dry bulb temperature

the temperature of air as measured by an ordinary thermometer.

Dry film thickness

the thickness, expressed in mils, of an applied and cured coating or mastic. For comparison, see Wet film thickness.

Dry-In or Dry-In Felt

usually the underlayment or the process of applying the underlayment for steep roofing.

Drying time

the time required for the loss of volatile components so that the material will no longer be adversely affected by weather conditions such as dew, rain, or freezing.

Dual level drain

in waterproofing, an outlet or other device with provisions for drainage at both the wearing surface level and the waterproofing membrane levels used to collect and direct the flow of runoff water from a horizontal slab.


the ability to withstand physical, chemical, or environmental abuse.

Dust Free

a surface is considered dust free when a finger can be lightly run over the surface without picking up any dirt, dust, or chalk on the finger.

Dynamic load

any load which is nonstatic, such as a wind load or a moving live load.


the lower edge of a sloping roof that projects beyond the wall.

Eave height

the vertical dimension from finished grade to the eave.


see Gutter.


polyepichlorohydrin, commonly referred to as epichlorohydrin. (see Epichlorohydrin.)

Edge stripping

membrane flashing strips cut to specific widths used to seal/flash perimeter edge metal and the roof membrane application of felt strips cut to narrower widths than the normal felt-roll width to cover a joint between metal perimeter flashing and built-up roofing.

Edge venting

the practice of providing regularly spaced or continuously protected (e.g., louvered) openings along a roof edge or perimeter, used as part of a ventilation system to dissipate heat and moisture vapor.


an encrustation of soluable salts, commonly white, deposited on the surface of stone, brick, plaster, or mortar, usually caused by free alkalies leached from mortar or adjacent concrete as moisture moves through it.


ethylene interpolymer.


the property of a body that causes it to tend to return to its original shape after deformation (as stretching, compression or torsion).


a macromolecular material that returns rapidly to its approximate initial dimensions and shape after substantial deformation by a weak stress and subsequent release of that stress.


the elastic, rubber-like properties of a material that will stretch when pulled and will return relatively quickly to its original shape when released.

Elastomeric coating

a coating that is capable of being stretched at least twice its original length (100 percent elongation) and recovering to its original dimensions.


a liquid, most often a solution, that will conduct current.


the ratio of the extension of a material to the length of the material prior to stretching.


(1) the process of pressing/positioning a felt, aggregate, fabric, mat, or panel into hot bitumen or adhesive to ensure intimate contact at all points; (2) the process of pressing/positioning granules into coating in the manufacture of factory-prepared roofing, such as shingles.


the loss of flexibility or elasticity of a material.


a mixture of bitumen and water, with uniform dispersion of the bitumen or water globules, usually stabilized by an emulsifying agent or system.

End lap

the distance of overlap where one ply, pane, or piece extends beyond the end of the immediately adjacent underlying ply, panel, or piece.

Envelope (Bitumen-stop)

a continuous membrane edge seal formed at the perimeter and at penetrations by folding the base sheet or ply over the plies above and securing it to the top of the membrane. The envelope prevents bitumen seepage from the edge of the membrane.


Ethylene propylene diene monomer (see also Ethylene propylene diene terpolymer.)

Epichlorohydrin (ECH)

a synthetic rubber including two epichlorohydrin based elastomers. It is similar to and compatible with EPDM.


a class of synthetic, thermosetting resins that produce tough, hard, chemical-resistant coatings and adhesives.

Equilibrium moisture content (EMC)

(1) the moisture content of a material stabilized at a given temperature and relative humidity, expressed as percent moisture by weight.

Equiviscous temperature (EVT)

the temperature at which a bitumen attains the proper viscosity for built-up membrane application.

Equiviscous temperature (EVT) application range

the recommended bitumen application temperature range. The range is approximately 25 degrees F (14 degrees C) above or below the EVT, thus giving a range of approximately 50 degrees F (28 degrees C). The EVT range temperature is measured in the mop cart or mechanical spreader just prior to application of the bitumen to the substrate.

Equiviscous temperature (EVT) for asphalt

the recommended EVT for roofing asphalt (ASTM D 312, Type I, II, III, or IV) is as follows Mop Application: the temperature at which the asphalt's apparent viscosity is 125 centipoise (0.125 Pa s). Mechanical Spreader Application: the temperature at which the asphalt's apparent viscosity is 75 centipoise (0.075 Pa s). Note: In order to avoid the use of two kettles if there are simultaneous mop and mechanical spreader applications, the EVT for mechanical spreader application can be used for both application techniques.

Equiviscous temperature (EVT) for coal tar

the recommended EVT for roofing coal tar (ASTM D 450, Type I or III) is the temperature at which the coal tar's apparent viscosity is 25 centipoise (0.025 Pa s).

Ethylene interpolymers (EIP)

a group of thermoplastic compounds generally based on PVC polymers from which certain single-ply roofing membranes can be formulated.

Ethylene propylene diene terpolymer (EPDM)

designated nomenclature of ASTM for a terpolymer of ethylene, propylene, and a diene. EPDM material is a thermosetting synthetic elastomer.


Equiviscous temperature.

Exhaust ventilation

air that is vented or exhausted from the roof cavity, typically through vents installed on the up slope portion of the roof. For example, with most steep-slope roof assemblies, exhaust vents are typically located at or near the ridge.


heat generated by a chemical reaction.

Expansion cleat

a cleat designed to accommodate thermal movement of the metal roof panels.

Expansion joint

a structural separation between two building elements that allows free movement between the elements without damage to the roofing or waterproofing system.

Exposed-nail method

a method of asphalt roll roofing application in which all nails are driven into the adhered, overlapping course of roofing. Nails are exposed to the weather.


(1) the traverse dimension of a roofing element or component not overlapped by an adjacent element or component in a roof covering. For example, the exposure of any ply in a built-up roof membrane may be computed by dividing the felt width, minus 2 inches (51 mm), by the number of shingled plies; thus, the exposure of 36 inch (914 mm) wide felt in a shingled, four-ply membrane should be approximately 81/2 inches (216 mm); (2) the dimension of sidewall or roofing covering that is not covered or overlapped by the up slope course of component. The typical exposure for a standard-size, 3-tab shingle is 5 inches (127 mm), depending upon manufacturer specifications.


a process in which heated or unheated material is forced through a shaping orifice (a die) in one continuously formed shape, as in film, sheet, rod or tubing.


a dormer, usually of small size, whose roof line over the upright face is typically an arched curve, turning into a reverse curve to meet the horizontal at either end. Also, a small shed roof projecting from the gable end of the larger, main roof area.


a woven cloth or material of organic or inorganic filaments, threads, or yarns used for reinforcement in certain membranes and flashings.

Factory Mutual Research (FMR)

commonly referred to as "FM," a research and testing organization that classifies roofing components and assemblies for their fire, traffic, impact (hail), weathering, and wind-uplift resistance for four major insurance companies in the United States.

Factory seam

a splice/seam made by the manufacturer during the assembly of sections of materials into larger sheets/panels.


any lightening of initial color.


a reduction in the softening point, sometimes caused by refluxing or overheating in a relatively closed container. (see Softening Point Drift.)


(1) in steep-slope roofing, a board that is nailed to the ends of a roof rafter; sometimes supports a gutter; (2) in a low-slope roofing, the vertical or steeply sloped roof or trim located at the perimeter of a building. Typically, it is a border for the low-slope roof system.


any of a wide variety of mechanical securement devices and assemblies, including nails, staples, screws, cleats, clips, and bolts, which may be used to secure various components of a roof assembly.

Feathering strips

tapered wood filler strips placed along the butt ends of old wood shingles to create a relatively smooth surface when reroofing over existing wood shingle roofs. Referred to in some regions of the country as "horse feathers" or leveling strips.


a flexible sheet manufactured by the interlocking of fibers with a binder or through a combination of mechanical work, mositure and heat. Felts are manufactured principally from wood pulp and vegetable fibers (organic felts), asbestos fibers (asbestos felts), glass fibers (glass fiber felts or ply sheets), or polyester fibers.

Felt machine (Felt Layer)

a mechanical device used for applying bitumen and roofing felt or ply sheet simultaneously.


a metal sleeve placed inside a gutter at the top. A spike or screw is nailed/screwed through the gutter face and ferrule into the fascia board to hold the gutter in place. The ferrule acts as a spacer in the gutter to maintain its original shape.

Fiberglass Insulation

blanket or rigid board insulation, composed of glass fibers bound together with a binder, faced or unfaced, used to insulate roofs and walls. Rigid boards usually have an asphalt and kraft paper facer.

Field of the Roof

the central or main portion of a roof, excluding the perimeter and flashing.

Field seam

a splice or seam made in the field (not factory) where overlapping sheets are joined together using an adhesive, splicing tape, or heat- or solvent-welding.


a relatively inert ingredient added to modify physical characteristics.


a heavy bead of waterproofing compound or sealant material generally installed at the point where vertical and horizontal surfaces meet; the desired effect to take out the 90 degree angle at the base of a vertical flashing.


sheeting having a nominal thickness not greater than 10 mils (0.25 mm).

Film thickness

the thickness of a membrane or coating. Wet film thickness is the thickness of a coating as applied; dry film thickness is the thickness after curing. Film thickness is usually expressed in mils (thousandths of an inch).


a term used to describe a deck surface condition. A sharp raised edge (generally in concrete) capable of damaging a roof membrane or vapor retarder.

Fine mineral-surfacing

water-insoluble, inorganic material, more than 50 percent of which passes through a No. 35 sieve. Used on the surface of various roofing materials and membranes to prevent sticking.

Fire resistance

the property of a material or assembly to withstand fire or give protection from it.

Fire retardant treated (FRT) plywood

plywood which has been impregnated, under pressure, with mineral salts; in the event of fire, the burning wood and salts emit noncombustible gases and water vapor instead of the usual flammable vapors.


(also referred to as an edge wrinkle) (1) a half-cylindrical or half-conical shaped opening or void in a lapped edge or seam, usually caused by wrinkling or shifting of ply sheets during installation; (2) in shingles, a half-conical opening formed at a cut edge.


in protective coatings, the detachment of small pieces of the coating film.

Flame retardant

a chemical used to impart flame resistance.

Flame spread

a propagation of a flame away from its source of ignition.


those characteristics of a material that pertain to its relative ease of ignition and ability to sustain combustion.


the projecting edge of a rigid or semi-rigid component, such as a metal edge flashing flange.

Flash point

the lowest temperature at which vapors above a volatile combustible substance ignite in air when exposed to a flame.


components used to weatherproof or seal the roof system edges at perimeters, penetrations, walls, expansion joints, valley, drains, and other places where the roof covering is interrupted or terminated. For example, membrane base flashing covers the edge of the field membrane, and cap flashings or counterflashings shield the upper edges of the base flashing.

Flashing cement

a trowelable mixture of solvent-based bitumen and mineral stabilizers that may include asbestos or other inorganic or organic fibers. Generally, flashing cement is characterized as vertical-grade, which indicate it is intended for use on vertical surfaces. (see Asphalt Roof Cement and Plastic Cement.)

Flashing collar

(sometimes referred to as a roof jack or flashing boot) an accessory flashing used to cover and/or seal soil pipe vents and other penetrations through the roof.

Flat lock

a method of interlocking metal panels in which one panel edge is folded back on top of itself and the other panel is folded under, after which the two panels are hooked together.


mats or felts composed of fibers, sometimes used as a membrane backer.

Flood (pour) coat

the surfacing layer of bitumen into which surfacing aggregate is embedded on an aggregate-surfaced built-up roof.

Flood test

the procedure where a controlled amount of water is temporarily retained over a horizontal surface to determine the effectiveness of the waterproofing system.

Fluid-applied elastomer

a liquid elastomeric material that cures after application to form a continuous waterproofing membrane.


method of application for roll materials by which the dry sheet is set into the bitumen or adhesive applied to the roof surface.


see Factory Mutual Research (FMR).

Foam stop

the roof edge treatment upon which SPF is terminated.


a strength or energy exerted or brought to bear; cause of motion or change.


Forest Products Laboratory.

Framed Opening

an opening in a wall or roof of a building, surrounded by structural framing, usually for field installed accessories such as skylights or ventilators.

Froth pack

a term used to describe small, disposable aerosol cans that contain SPF components. Two component froth packs are available to do small repairs for sprayed polyurethane foam-based roofs.


a designation for galvanized metal sheet, indicating 0.90 ounces (26 g) of zinc per square foot, measured on both sides.


the vertical triangular portion of the end of a building having a double-sloping roof, from the level of the eaves to the ridge of the roof.

Gable roof

a single-ridge roof that terminates at gable end(s).

Gable-Shaped Roof

a single-ridge roof that terminates at gable end(s). (See Figure 11.)


trade name for a metal alloy coating that is composed of aluminum, zinc and silicone.

Galvanic action

an electrochemical action that generates electrical current between two metals of dissimilar electrode potential.

Galvanic series

an list of metals and alloys arranged according to their relative electrolytic potentials in a given environment.


to coat steel or iorn with zinc.

Galvanized steel

steel coated with zinc for corrosion resistance.


a roof that has two pitches on each side, where the upper roof area has less slope than the lower roof areas.


a metal thickness measurement.


a prefabricated water drainage material used to relieve hydrostatic pressure against waterproofing and promote drainage.

Geodesic Dome

a rounded structure made of short, straight, triangular sections that form polygons. (See Figure 13.)


a tightly woven fabric used to restrict the flow of fine soil particles and other contaminants while allowing water to pass freely through; used to protect drainage systems from clogging.


a horizontal beam that supports wall cladding between columns.

Glass felt

glass fibers bonded into a sheet with resin and suitable for impregnation with asphalt in the manufacture of bituminous waterproofing, roofing membranes and shingles.

Glass fiber insulation

blanket or rigid board insulation, composed of glass fibers bound together with a binder, faced or unfaced, used to insulate roofs and walls.

Glass mat

a thin mat of glass fibers with or without a binder.

Glaze coat

(1) the top layer of asphalt on a smooth-surfaced built-up roof membrane; (2) a thin protective coating of bitumen applied to the lower plies or top ply of a built- up roof membrane when application of additional felts or the flood coat and aggregate surfacing are delayed. (also see Flood coat.)


the shine, sheen, or luster of a dried film.


a unit used to measure in the English System of units; 7,000 grains equals 1 lb.; used as a measure of the weight of moisture in air.


(also referred to as mineral or ceramic granule) opaque, natural, or synthetically colored aggregate commonly used to surface cap sheets, shingles, and other granule-surfaced roof coverings.


coarse granular aggregate resulting from the natural erosion of rock.

Gravel stop

a flanged device, frequently metallic, designed to prevent loose aggregate from washing off the roof and to provide a continuous finished edge for the roofing.

Groundwater level

at a particular site, the level below which the subsoil and rock masses of the earth are fully saturated with water.


a mixture of cement, sand, and water used to fill cracks and cavities in masonry.

Grout (Non-Shrink)

a cementitious material used to fill pitch-pans/pockets, prior to the application of a pourable sealer.


used at the bottom of a steep-slope roof system valley, a large flat metal piece(s) wider than the valley to help prevent build-up at the base of the valley, either from debris or ice dam formations.


a channeled component installed along the downslope perimeter of a roof to convey runoff water from the roof to the drain leaders or downspouts.

Gypsum board panels

cementititious board stock with noncombustible core primarily comprised of gypsum that is commonly used as a barrier board thermal barrier or cover board in a roof assembly.


method of spot applying asphalt-based adhesive to shingles for securement and wind resistance.


the relative resistance of a material to indentation.


the distance of overlap measured from the uppermost ply or course to the point where it laps over the undermost ply or course.

Heat Aging

controlled exposure of materials to elevated temperatures over time.

Heat flow

the quantity of heat transferred to or from a system in a unit of time.

Heat seaming

the process of joining thermoplastic films, membranes, or sheets by heating and then applying pressure to bring both materials in contact with each other. (see Heat welding.)

Heat transfer

the transmission of thermal energy from a location of higher temperature to a location of lower temperature. This can occur by conduction, convection, or radiation.

Heat welding

method of melting and fusing together the overlapping edges of separate sheets or sections of polymer modified bitumen, thermoplastics or some uncured thermoset roofing membranes by the application of heat (in the form of hot air or open flame) and pressure. (see Heat seaming.)


the edge created by folding metal back on itself.


the inclined external angle formed by the intersection of two sloping roof planes.

Hip roof

a roof that rises by inclined planes to form one or more hips.


a mechanical lifting device.


an area where a liquid-applied material is missing or absent.


voids left in concrete resulting from failure of the mortar to effectively fill the spaces among course aggregate particles.

Hot or Hot stuff

a roofing worker's term for hot bitumen.


the subjective perception of color such as red, yellow, green, blue, purple or some combination; white, black or gray possess no hue.


the condition of the atmosphere with respect to water vapor. See relative humidity.


heating, ventilating, and air conditioning equipment.

Hybrid roof covering

combination of two or more separate and distinct roof membranes; e.g., three ply smooth BUR and a modified bitumen cap.


the chemical reaction by which a substance (such as Portland cement) combines with water, giving off heat to form a crystalline structure in its setting and hardening.


an organic chemical compound primarily containing the elements carbon and hydrogen.

Hydrostatic pressure

the pressure equivalent to that exerted on a surface by a column of water of a given height.

Hydrostatic pressure relief system

a system of perimeter and/or under slab drains used to regulate the hydrostatic pressure in the earth surrounding a below-grade structure.


attracting, absorbing and retaining atmosphere moisture.


a registered trademark of E.I. duPont de Nemours & Co., for "chlorosulfonated polyethylene" (CSPE). (see Chlorosulfonated polyethylene.)


a decorative steep-sloped roof on the perimeter of a building.

Mansard roof

a steeper roof that terminates into a flat roof at its high point.


construction, usually set in mortar, of natural building stone or manufactured units, such as brick, concrete block, adobe, glass block, tile, manufactured stone or gypsum block.


a thick adhesive material used as a cementing agent for holding waterproofing membrane in place. (see Asphalt roof cement).


a thin layer of woven, non-woven, or knitted fiber that serves as reinforcement to the material or membrane.

Mat slab

a concrete slab designed with reinforcement to resist the uplift forces created by hydrostatic pressure.

Material safety data sheets (MSDS)

a written description of the chemicals in a product and other pertinent data including such things as safe handling and emergency procedures. In accordance with OSHA regulations, it is the manufacturer's responsibility to produce an MSDS and the employer's responsibility to communicate its contents to employees.


formerly Metal Builders Dealers Association, now Systems Builders Association.


Metal Building Manufacturers Association


Metal Construction Association

Mechanical damage

in SPF-based roofing, physical damage to a completed SPF-based roof system not caused by normal wear and tear.

Mechanically-fastened membranes

generally used to describe membranes that have been attached at defined intervals to the substrate.


a flexible or semi-flexible roof covering or waterproofing whose primary function is to exclude water.


any of various opaque, fusible, ductile and typically lustrous substances that are good conductors of electricity and heat.

Metal Film

a layer of foil made from a single metallic substance, or from an alloy, that is laminated to a membrane during manufacture. The metal foil serves as the weathering surface of the membrane or flashing material.

Metal Flashing

accessory components fabricated from sheet metal and used to weatherproof terminating roof covering edges. Frequently used as through-wall flashing, cap flashing (coping), counterflashing, step-flashing, etc. (See Flashing.)

Metal rain collar

a metal counterflashing used to wrap a penetration and prevent water infiltration though the top of the penetration base flashing.

Metal roof panel

an interlocking metal sheet having a minimum installed weather exposure of 3 square feet (279000 mm2 or 0.28 m2)per sheet.

Metal roof shingle

an interlocking metal sheet having an installed weather exposure less than 3 square feet (279000 mm2 or 0.28 m2) per sheet.

Metallic waterproofing

consist of finely graded iron particles combined with an oxidizing catalyst. When mixed with water (or water, cement, and sand), the finely distributed particles expand, creating a waterproof layer that becomes a part of the surface to which it is applied.


unit of length measurement in the metric system, 1 meter is equal to 39.37 inches.

Mica Dust

crystallized complex silicate minerals that are pulverized into dust form for use as a release agent. (See Talc.)

Microbiological Resistance

the ability of a material to resist attack and degradation by various air- and soil-borne micro-organisms.


the absorption of oil or vehicle from a compound into an adjacent porous surface.


a unit of measure, one mil is equal to 0.001 inches, or 25.4 micrometers (um), often used to indicate the thickness of a roofing membrane.


a superficial growth produced on organic matter or living plants by fungi.


a unit of measure equal to one thousandth (0.001) of a meter, or 0.03937 inches.


Mineral Insulation Manufacturers Association

Mineral fiber

insulation composed principally of fibers manufactured from rock, slag or glass, with or without binders.

Mineral granules

see Granules.

Mineral stabilizer

a fine, water-insoluble inorganic material, used in a mixture with solid or semi-solid bituminous materials.

Mineral-surfaced roofing

roofing materials whose surface or top layer consists of granule-surfaced sheet.

Mineral-surfaced sheet

a roofing sheet that is coated on one or both sides with asphalt and surfaced with mineral granules.


the joint produced by joining two diagonally cut pieces.

Miter joint

a joint between two members at an angle to each other; each member is cut at an angle equal to half the angle of the junction; usually the members are at right angles to each other.

Model (building) codes

a compilation of standards or codes established to provide uniformly in regulations pertaining to building construction.

Model Codes

a compilation of standards or codes established to provide uniformity in regulations pertaining to building construction. Examples ICBO - International Conference of Building Officials; BOCA - Building Officials and Code Administrators; SBC - Standard Building Code.

Modified bitumen

(1) a bitumen modified by including one or more polymers (e.g., atactic polypropylene, styrene butadiene styrene, etc.); (2) composite sheets consisting of a polymer modified bitumen often reinforced with various types of mats or films and sometimes surfaced with films, foils or mineral granules.

Moisture contour map

a map used to graphically define the location of moisture within a roof assembly after a moisture scan has been performed.

Moisture relief vent

a venting device installed through the roofing membrane to relieve moisture vapor pressure from within the roofing system.

Moisture scan

the use of a mechanical device (capacitance, infrared, or nuclear) to detect the presence of moisture within a roof assembly. (see Non-destructive testing.)

Mole run

a meandering ridge in a roof membrane not associated with insulation or deck joints.


formed from or composed of a single material; seamless.


a low-molecular-weight substance consisting of molecules capable of reacting with like or unlike molecules to form a polymer.


an application procedure in which roofing elements (insulation boards, felt plies, cap sheets, etc.) are initially placed upside down adjacent to their ultimate locations; coated with adhesive or bitumen; and turned over and adhered to the substrate.


the application of hot bitumen with a mop or mechanical applicator to the substrate or plies of a bituminous membrane. There are four types of mopping. Solid mopping: a continuous coating. Spot mopping: bitumen is applied roughly in circular areas, leaving a grid of unmopped perpendicular areas. Sprinkle mopping: bitumen is shaken onto the substrate from a broom or mop in a random pattern. Strip mopping: bitumen is applied in parallel bands.

Mud cracking

surface cracking resembling a dried mud flat.

Mud slab

a layer of concrete, typically 2 inches (50 mm) to 6 inches (150 mm) thick, used as the substrate for membrane waterproofing.

Multiple Coat

two or more layers of coating applied to a substrate.


National Association of Home Builders


(sometimes referred to as blocking) a piece or pieces of dimensional lumber and/or plywood secured to the structural deck or walls, which provide a receiving medium for the fasteners used to attach membrane or flashing.


the application of nails. May be (1) exposed nailing of roofing wherein nail heads are exposed to the weather; (2) concealed nailing of roofing wherein nail heads are concealed from the weather by an overlapping material.


acrylonitrile butadiene polymer blend. One proprietary NBP membrane is commonly referred to as nitrile butadiene copolymer.

Needle Punched Fabric

a fabric where barbed needles (in multiple punches) achieve mechanical bonding/locking or carding of fibers.

Negative side waterproofing

an application wherein the waterproofing system and source of hydrostatic pressure are on opposite sides of the structural element.


a synthetic rubber (polychloroprene) used in liquid and sheet-applied elastomeric roof membranes or flashings.


(1) the installation of new metal roof deck directly on top of existing metal roof deck; (2) a method of reroofing with new asphalt shingles over existing shingles in which the top edge of the new shingle is butted against the bottom edge of the existing shingle.

Net free vent area

the area (measured in square inches) open to unrestricted air flow and commonly used as a yardstick to measure relative vent performance; the area of the opening of a vent minus the area displaced by the screening material.

Newton (N)

SI unit of measure for force.


National Insulation Contractors Association

Night seal (or night tie-in)

a material and/or method used to temporarily seal a membrane edge during construction to protect the roofing assembly in place from water penetration. Usually removed when roofing application is resumed.


a prepared organic felt roll roofing with a granule surfacing that has a mass of approximately 90 pounds per 100 square feet, (4400 g/m²).


National Institute of Standards and Technology

Nitrile alloy

an elastomeric material of synthetic non-vulcanizing polymers.

Nitrile rubber

a membrane whose predominant resinous ingredient is a synthetic rubber made by the polymerization of acrylonitrile with butadiene.

No-cutout shingles

shingles consisting of a single solid strip with no cutouts.


in reference to metal, inert; opposite of active.

Noble metal

a metal that readily receives electrons from an anodic metal (see Galvanic series).

Non-Breathing Membrane

a membrane that does not allow significant amounts of water vapor or air to pass through; which has a perm rating 1.0 or less per ASTM E 96, Procedure E.

Non-traffic bearing

for waterproofing purposes, a membrane system requiring some form of protection barrier and wearing surface.

Non-Vulcanized Membrane

a membrane manufactured from thermoplastic compounds that retains its thermoplastic properties throughout the service life of the membrane.

Nondestructive testing (NDT)

a method to evaluate the disposition, strength or composition of materials or systems without damaging the object under test. Typically used to evaluate moisture content in roofing assemblies, the three common test methods are electrical capacitance, infrared thermography and nuclear back-scatter.


not easily ignited and not burning rapidly if ignited.


a material that, when dry, cannot be crumbled, pulverized or reduced to powder by hand pressure.


a material which resists oxidation in exterior exposures or accelerated weathering.

Nonvolatile content

the portion of a coating that does not evaporate during drying or curing under specified conditions, comprising the binder and, if present, the pigment. (The percent volatile content is obtained by subtracting the nonvolatile content from 100.).


a term used to describe the random arrangement of reinforcing fibers (glass, polyester, etc.) in a mat or scrim.

Nonwoven fabric

a textile structure produced by bonding or interlocking of fibers, or both, accomplished by mechanical, chemical, thermal, or solvent means and combinations thereof.


National Roofing Contractors Association.


National Tile Roofing Manufacturers Association

Nuclear hydrogen detection (NHD) meter

a device that contains a radioactive source to emit high velocity neutrons into a roof system. Reflecting neutrons are measured by a gauge that is used to detect hydrogen; the quantity of hydrogen detected may be linked to the pressure of water.

Nuclear Testing (Nuclear Back-Scatter)

a device that contains a radioactive source to emit high velocity neutrons into a roof system. Reflecting neutrons are measured by a gauge that is used to detect moisture.


generic name for a family of polyamide polymers, used as a scrim in some fabric-reinforced sheeting.


a platform (typically wooden) used for storing and shipping materials.


the bottom flat part of a roofing panel which is between the ribs of the panel.

Pan former

power roll-forming equipment that produces a metal roofing panel from a flat sheet.

Parapet wall

the part of a perimeter wall that extends above the roof.


in masonry construction, a coat of cement mortar on the face of rough masonry, the earth side of foundation and basement walls, or the like.

Partially attached

a roofing assembly in which the membrane has been "spot affixed" to a substrate, usually with an adhesive or a mechanical device.

Parting agent

a material applied to one or both surfaces of a sheet to prevent blocking.


SI unit of measure for force per unit area.


1) a layer of material, usually applied by the spray method, that is allowed to reach cure before another layer ("pass") is applied; 2) a term used to explain a spray motion of the foam gun in the application of the spray polyurethane foam (SPF) material. The speed of the pass controls the thickness of the SPF.

Pass line

the junction of two passes of SPF. A distinct line is formed by the top skin of the bottom pass and the next pass adhering to this skin.


a support or base for roof top components such as pavers, pipes and small roof top units.

Peel strength

the average load per unit width required to separate progressively a flexible member from a rigid member or another flexible member.


(1) any construction (e.g., pipes, conduits, HVAC supports) passing through the roof; (2) the consistency of a bituminous material expressed as the distance, in tenths of a millimeter (0.1 mm), that a standard needle penetrates vertically into a sample of material under specified conditions of loading, time, and temperature.

Percent Elongation

in tensile testing, the increase in the gauge length of a specimen measured at or after fracture of the specimen within the gauge length. Usually expressed as a percentage of the original gauge length.


an aggregate used in lightweight insulating concrete and preformed perlitic insulation boards, formed by heating and expanding siliceous volcanic glass.


see Permeance.


(1) the capacity of a porous material to conduct or transmit fluids; (2) the time rate of vapor transmission through unit area of flat material of unit thickness induced by unit vapor pressure difference between two specific surfaces, under specified temperature and humidity conditions. The English (inch.pound) unit of measurement for permeability is gr/hr.ft2.(in. Hg/in.), which is commonly referred to as "perm.inch" units.


(1) the rate of water vapor transmission per unit area at a steady state through a material, membrane, or assembly; (2) the time rate of water vapor transmission through unit area of flat material or construction induced by unit vapor pressure difference between two specific surfaces, under specified temperature and humidity conditions. The English (inch.pound) unit of measurement for permeance is gr/ Hg, which is commonly referred to as "perm" units.


a measure of the acidity or alkalinity of a solution, with neutrality represented by a value of 7, with increasing acidity represented by increasingly smaller values, and with increasing alkalinity represented by increasingly larger values.

Phased application

the installation of a roofing or waterproofing system during two or more separate time intervals or different days. Application of surfacings at different time intervals are typically not considered phased application. (see Surfacing.) A roofing system not installed in a continuous operation.

Picture framing

a square or rectangular pattern of ridges in a roof membrane or covering over insulation or deck joints.


an insoluble compounding material used to impart color.


Polyisocyanurate Insulation Manufacturers Association


a tiny hole in a coating, film, foil, membrane, or laminate comparable in size to one made by a pin.

Pipe boot

prefabricated flashing piece used to flash around circular pipe penetrations.


see Coal tar.

Pitch-pocket (Pitch-pan)

a flanged, open bottomed enclosure made of sheet metal or other material, placed around a penetration through the roof, filled with grout and bituminous or polymeric sealants to sealants to seal the area around the penetration.

Pittsburgh lock seam

a method of interlocking metal, usually at a slope change.

Plastic cement

a roofing industry generic term used to describe asphalt roof cement that is a trowelable mixture of solvent-based bitumen, mineral stabilizers, and other fibers and/or fillers. Generally, intended for use on relatively low slopes, not vertical surfaces. (also see Asphalt roof cement and Flashing cement.)

Plastic Film

a flexible sheet made by the extrusion of thermoplastic resins.


a material incorporated in a material to increase its ease of workability, flexibility or distensibility.

Plasticizer migration

in some thermoplastic roofing membranes, the loss of plasticizer chemicals from the membrane, resulting in shrinkage and embrittlement of the membrane, typically PVC.


a plastic-like polymer consisting of any of various complex organic compounds produced by polymerization, and capable of being molded, extruded, or cast into various shapes or films.


the material property of being flexible or moldable.


a layer of felt or ply sheet in a built-up roof membrane or roof system.


protected membrane roof.


see Neoprene.


a polymer in which the repeated structural unit in the chain is of the ester type.

Polyester Fiber

a synthetic fiber usually formed by extrusion. Scrims made of polyester fiber are used for fabric reinforcement.

Polyisobutylene (PIB)

a product formed by the polymerization of isobutylene. May be compounded for use as a roof membrane material.


a macromolecular material formed by the chemical combination of monomers having either the same or different chemical composition.

Polymer modified bitumen

see Modified bitumen.

Polymeric methylene diphenyl diisocyanate (PMDI)

component A in SPF. An organic chemical compound having two reactive isocyanate groups. It is mixed with the B component to form polyurethane.


a chemical reaction in which monomers are linked together to form polymers.


a polyhydric alcohol, i.e., one containing three or more hydroxyl groups, one component of polyisocyanurate and polyurethane compounds.


a polymer prepared by the polymerization of propylene as the sole monomers.


a polymer prepared by the polymerization of styrene as the sole monomer.

Polyvinyl chloride (PVC)

a synthetic thermoplastic polymer prepared from vinylchloride. PVC can be compounded into flexible and rigid forms through the use of plasticizers, stabilizers, fillers, and other modifiers. Rigid forms are used in pipes; flexible forms are used in the manufacture of sheeting and roof membrane materials.


a surface which is incompletely drained.


the excessive accumulation of water at low-lying areas on a roof that remains after the 48 hours after the end rainfall under conditions conducive to drying.

Pop rivet

a relatively small-headed pin with an expandable head for joining light gauge sheet metal.

Popcorn surface texture

in SPF roofing, the condition in which the foam surface shows a coarse texture where valleys form sharp angles. This surface is unacceptable for proper coating and protection.

Positive drainage

the drainage condition in which consideration has been made during design for all loading deflections of the deck and additional roof slope has been provided to ensure drainage of the roof area within 48 hours of rainfall during conditions conducive to drying.

Positive side waterproofing

an application where the waterproofing systems and the source of the hydrostatic pressure are on the same side of the structural element.

Pot life (Working life)

the period of time during which a reacting composition remains suitable for its intended processing after mixing with reaction initiating agents.

Pourable sealer

a type of sealant often supplied in two parts and used at difficult-to-flash penetrations, typically in conjunction with pitch-pockets to form a seal.


coating a metal with solder or tin alloy prior to soldering or brazing it.

Press brake

a machine used in cold-forming sheet metal or strips of metal into desired profiles.

Prestressed concrete

concrete in which the reinforcing cables, wires, or rods in the concrete are tensioned before there is load on the structural member, holding the concrete in compression for greater strength.


(1) a thin, liquid-applied solvent-based bitumen that may be applied to a surface to improve the adhesion of subsequent applications of bitumen; (2) a material which is sometimes used in the process of seaming single-ply membranes to prepare the surfaces and increase the strength (in shear and peel) of the field splice; (3) a thin liquid-applied material that may be applied to the surface of SPVF to improve the adhesion of subsequent application of SPVF protective coatings.


the basic pumping unit for SPF or two-component coating systems. Consists of two positive displacement pumps designed to dispense two components at a precisely controlled ratio.

Protected membrane roof (PMR)

an insulated and ballasted roofing assembly in which the insulation and ballast are applied on top of the membrane (sometimes referred to as an "inverted roof assembly").

Protection course

a sacrificial material used to shield a waterproofing material from damaging external forces.

Protection mat

a sacrificial material used to shield one roof system component from another.


an instrument used to measure humidity in the atmosphere from two thermometers which are similar except that the bulb of one is kept wet, the bulb of the other being dry.

Psychrometric chart

chart showing the relationship between dew point temperature, dry bulb temperature, wet bulb temperature and relative humidity.

Puncture resistance

the ability of a material to withstand the action of a penetrating or puncturing object.


horizontal secondary structural member that transfers loads from the primary structural framing.


polyvinyl chloride.


see Thermal resistance.


a method of asphalt shingle application, also referred to as the straight-up method, whereby shingle courses are applied vertically, up the roof rather than laterally or across and up.


one of a series of sloped structural members, that extend from the ridge or hip to the downslope perimeter or eave, designed to support the roof deck and its associated loads.


a groove or slot, often cut in a masonry wall or other vertical surface adjoining a roof, for inserting an inset flashing component such as a reglet.


the sloped edge of a roof at or adjacent to the first or last rafter.

Rake-starter (Bleeder strip)

starter-strip used along rake edges in conjunction with asphalt shingle roofing.


Roof Consultants Institute


Roof Coatings Manufacturers Association


Roof Deck Contractors Association


the addition of a new roof membrane or steep-slope roof covering over a major portion of an existing roof assembly. This process does not involve removal of the existing roofing.


see Light reflectance.


a sheet metal receiver for the attachment of counterflashing. A reglet may be surface-mounted, inset into a raggle or embedded behind cladding.

Reinforced membrane

a roofing or waterproofing membrane that has been strengthened by the addition or incorporation of one or more reinforcing materials, including woven or nonwoven glass fibers, polyester mats or scrims, nylon, or polyethylene sheeting.

Relative humidity (RH)

the ratio of the pressure of water vapor present in a given volume of air to the pressure of fully saturated water vapor at the same temperature, expressed as a percentage.

Release tape (or strip)

a plastic film or paper strip that is applied to the back of self-sealing shingles and other materials. The strip prevents the material from sticking together in the roll or bundle. With asphalt shingles, the strip need not be removed for application of the shingles.


the practice of removing an existing roof system down to the roof deck and replacing it with a new roofing system.


the process of re-covering, or tearing-off and replacing an existing roof system.


component B in SPF. This component contains a catalyst, blowing agent, fire retardants, surfactants and polyol. It is mixed with the A component to form polyurethane.

Resistance, Thermal

the average temperature difference between two defined surfaces of a particular body or assembly when unit thermal transmission in unit time through unit area is established between the surfaces. R=_Fòhòsòft2/Btu (R=Kòm2/W).


highest point on the roof, represented by a horizontal line where two roof areas intersect, running the length of the area.

Ridge cap

a material or covering applied over the ridge of a roof.

Ridge course

the last or top course of roofing materials, such as tile, roll roofing, shingles, etc., that covers the ridge and overlaps the intersecting field roofing.

Ridge vent

a ventilator located at the ridge that allows the escape of warm and/or moist air from the attic area or rafter cavity.


see Buckle.


Roofing Industry Educational Institute


Rubber Manufacturers Association

Roll Goods

a general term applied to rolls of roofing felt, ply sheet, etc., which are typically furnished in rolls.

Roll materials

a general term applied to rolls of roofing felt, ply sheet, etc., which are typically furnished in rolls.

Roll roofing

coated felts, either smooth or mineral-surfaced.


(1) the cover of a building; (2) to cover with a roof.

Roof area divider

refer to area divider.

Roof area expansion joint

see expansion joint.

Roof assembly

an assembly of interacting roof components including the roof deck, vapor retarder (if present), insulation, and roof covering.

Roof cement

see Asphalt roof cement or Coal tar roof cement.

Roof covering

the exterior roof cover or skin of the roof assembly, consisting of membrane, panels, sheets, shingles, tiles, etc.

Roof curb

raised frame used to mount mechanical units (such as air conditioning or exhaust fans), skylights, etc. on a roof.

Roof Diaphragm

a structural roof deck that is capable of resisting shear that is produced by lateral forces, such as wind or seismic loads.

Roof jack

a metal or wood bracket used to support toe-boards on steep-slope roofs. (also see Flashing Collar.)

Roof or Roofer's Cement

see Asphalt Roof Cement or Coal Tar Roof Cement.

Roof overhang

a roof extension beyond the exterior wall of a building.

Roof seamer

(1) machine that crimps neighboring metal roof panels together; (2) machine that welds laps of membrane sheets together using heat, solvent, or dielectric energy.

Roof slope

the angle a roof surface makes with the horizontal, expressed as a ratio of the units of vertical rise to the units of horizontal length (sometimes referred to as run). For English units of measurement, when dimensions are given in inches, slope may be expressed as a ratio of rise to run, such as 4:12 or as an angle.

Roof system

a system of interacting roof components, generally consisting of membrane or primary roof covering and roof insulation (not including the roof deck) designed to weatherproof and, sometimes, to improve the building's thermal resistance.


craftsman who applies roofing materials.

Rosin paper (specifically Rosin-sized sheathing paper)

a nonasphaltic paper used as a sheathing paper or slip sheet in some roof systems.


a material that is capable of recovering from large deformations quickly and forcibly.


horizontal dimension of a slope.

Rust Blush

the earliest stage of rusting characterized by the orange or red color. Occurs frequently on freshly sand blasted steel if allowed to stand too long before coating.


a small tapered/sloped roof area structure that helps to channel surface water to drains. Frequently located in valley. A saddle is often constructed like a small hip roof or pyramid with a diamond-shaped base. (see Cricket.)


undesirable excessive flow in material after application to a surface.

Saturated felt

a felt that has been immersed in hot bitumen; the felt adsorbs as much bitumen as it can retain under the processing conditions, but remains porous and contains voids.


Systems Builders Association


Southern Building Code Congress International, Inc.


see Styrene butadiene styrene.


shaped by grinding.


the process of striking off excess concrete to bring the top surface of the concrete to the proper finish and elevation.

Screen wall

a nonstructural wall erected around units or curbs on a roof. Typically the framing consists of girts with a wood or metal covering attached to the frame.


a woven, nonwoven or knitted fabric composed of continuous strands of material used for reinforcing or strengthening membranes.


drainage device in the form of an outlet through a wall, parapet wall or raised roof edge lined with a soldered sheet metal sleeve.


a hatch that provides access to the roof from the interior of the building.


Steel Deck Institute.


(1) a generic term for a function that prevents or controls the passage of water; (2) to secure a roof or structure from the entry of moisture.


(1) a material that has the adhesive and cohesive properties to form a seal; (2) a mixture of polymers, fillers, and pigments used to fill and seal joints where moderate movements is expected; unlike caulking, it cures to a resilient solid.

Sealant backing

a compressible material placed in a joint before applying a sealant.


a coating designed to prevent excessive absorption of finish coats into porous surfaces; a coating designed to prevent bleeding.

Sealing washer

a rubber or neoprene washer, sometimes metal-backed, typically placed on a fastener to prevent water from migrating into a through the fastener hole.


a joint formed by mating two separate sections of material. Seams can be made or sealed in a variety of ways, including adhesive bonding, hot-air welding, solvent welding, using adhesive tape, sealant, etc.

Seam sample

in single-ply and sometimes modified bitumen membrane roofing, a sample from the membrane that extends through the side lap of adjacent rolls of membrane, taken for the purpose of assessing the quality of the seam.

Seam Strength

the force or stress required to separate or rupture a seam in the membrane material.

Self-adhering membrane

a membrane that can adhere to a substrate and to itself at overlaps without the use of an additional adhesive. The undersurface of a self-adhering membrane is protected by a release paper or film, which prevents the membrane from bonding to itself during shipping and handling.

Self-drilling screw

a fastener that taps and drills its own hole during application.

Self-sealing shingle

an asphalt shingle containing factory-applied strip or spots of heat sensitive adhesive intended to adhere the overlying shingle once installed on the roof and warmed by the sun.

Self-tapping screw

a fastener that forms receiving threads when turned in a previously drilled hole.

Self-Vulcanized Membrane

a membrane manufactured from compounds that are thermoplastic during manufacture and installation, but whose polymers eventually cross-link and cure during exposure.


(1) an edge or edging that differs from the main part of a fabric, granule-surfaced roll roofing or cap sheet, or other material; (2) a specially defined edge of the material (lined for demarcation), which is designed for some special purpose, such as overlapping or seaming.

Selvage Edge

an edge designed for certain sheet good materials, e.g., mineral-surfaced sheets. With mineral surfaced sheets, the surfacing is omitted over a portion of the longitudinal edge of the sheet (e.g., mineral surface cap sheet) in order to obtain better adhesion of the overlapping sheet.

Separator layer

refer to Slip sheet.

Service temperature limits

the minimum or maximum temperature at which a coating, SPF, or other material will perform satisfactorily.


to convert into a fixed or hardened state by chemical or physical action.


slight differences in surfacing color, such as shingle granule coloring, that may occur as a result of manufacturing operations.

Shark fin

an upward-curled felt side lap or end lap.

Shear strength

the resistance to forces that cause or tend to cause two contiguous parts of the body to slide relative to each other in a direction parallel to their contrast.

Shed roof

a roof having only one sloping plane and no hips, ridges or valleys.

Shelf life

the maximum time a package material can be stored under specified conditions and still meet the performance requirements specified.


(1) a small unit of prepared roofing designed for installation with similar units in overlapping rows or courses on inclines normally exceeding 3:12 slope (14 degrees); (2) to cover with shingles; (3) to apply any sheet material in succeeding overlapping rows like shingles.


(1) the application of shingles; (2) the procedure laying parallel felts so that one longitudinal edge of each felt overlaps and the other longitudinal edge overlaps an adjacent felt. Normally felts are shingled on a slope so that water flows over rather than against each lap.

Shore "A" Hardness

a measure of firmness of a material by means of a Durometer Hardness Gauge. (A measure of 20 is about the firmness of a gum eraser; 90 is about that of a rubber heel.)


a decrease in one or more dimensions of an object or material.

Shrinkage crack

in waterproofing, a separation in a material, such as a concrete substrate, caused by the inability of the material to resist a reduction in size which occurs during its hardening or curing process or both.


an abbreviation for the International System of Units (Le Systeme International d'Unites).

Side lap

the continuous longitudinal overlap of neighboring like materials.

Side lap fastener

a fastener used to connect adjacent panels together at the side lap.

Side Lap-Ganging

pattern or application for roofing materials, as related to the amount of cover or side overlap of adjacent like materials.


the finish covering of an exterior wall of a frame building; the siding may be cladding material such as wood, aluminum or vinyl (but not masonry).


an apparatus with square apertures for separating sizes of material.

Silicone-based Water Repellants

any of the organopolysiloxanes (silicone derivative) applied to masonry materials for dampproofing or repelling water.


the bottom horizontal framing member of an opening, such as below a window or door.

Sill flashing

a flashing of the bottom horizontal framing member of an opening, such as below a window or door.

Single Coverage

roofing material that provides one layer over the substrate to which it is applied.

Single-lock standing seam

a standing seam that uses one overlapping interlock between two seam panels, in contrast with the double interlocking used in a double standing seam.

Single-ply membranes

roofing membranes that are field applied using just one layer of membrane material (either homogeneous or composite) rather than multiple layers.

Single-ply roofing

a roofing system in which the principal roof covering is a single layer flexible membrane often of thermoset or thermoplastic membrane.


the condition created by the overlapping intersection of three or four sheets in the membrane.


the exposed portion of strip shingles defined by cutouts.

Tack-free time

in SPF-based roofing, a curing phase of polyurethane foam to when the material is no longer sticky. When the polyurethane foam is tack free, it can be sprayed over with another pass, referred to as a "lift". With some care the polyurethane foam can be walked on soon after it is tack free.


whitish powder applied at the factory to the surface of some roofing materials (e.g., vulcanized EPDM membranes), used as a release agent to prevent adhesion of the membrane to itself.

Tapered edge strip

a tapered insulation strip used to (1) elevate and slope the roof at the perimeter and at curbs, and (2) provide a gradual transition from one layer of insulation to another.


(1) the technique of connecting joints between insulation boards or deck panels with tape; (2) the technique of using self-adhering tape-like materials to seam or splice single-ply membranes.


a brown or black bituminous material, liquid or semi-solid in consistency, in which the predominating constituents are bitumens obtained as condensates in the processing of coal, petroleum, oil-shale, wood, or other organic materials.

Tar boils

bubbles of moisture vapor encased in a thin film of bitumen, also known as "blackberries."

Tarred felt

see Coal tar felt.

Tear resistance

the load required to tear a material, when the stress is concentrated on a small area of the material by the introduction of a prescribed flaw or notch. Expressed in psi (pounds force) per inch width or kN/m (kilonewton per meter width).

Tear strength

the maximum force required to tear a specimen.

Tear-off and reroof

the removal of all roof system components down to the structural deck, followed by installation of a completely new roof system.

Tensile Fatigue Resistance

the ability of a given membrane material to resist "fatigue" and/or other damage (such as loss of elasticity) caused by the alternate stretching and relaxing of the material over a period of time.

Tensile strength

the strength of a material under tension as distinct from torsion, compression or shear.

Tensile Test

a test in which a specimen is subjected to increasing longitudinal pulling stress until fracture occurs.

Tension leveling

the process of pulling metal coil stock between two spools under a certain pressure to help reduce side camber and potential oil canning in the coil stock caused by manufacturing and cutting processes.


the treatment or method of anchoring and/or sealing the free edges of the membrane in a roofing or waterproofing system.


an alloy of lead and tin, used to coat sheets of carbon steel or stainless steel for use as metal roofing sheet.

Terra cotta

low-fired clay, either glazed or unglazed.

Test cut

a sample of the roof system or assembly which exposes the roof deck and is used to diagnose the condition of the membrane, evaluate the type and number of plies or number of membranes, or rates of application (e.g., the weight of the average interply bitumen moppings).

Thatch Roof

the covering of a roof usually made of straw, reed, or natural foliage (palms) bound together to shed water.


a unit of heat equivalent to 100,000 BTUs (105.6 x 106). Commonly used by utilities in quoting prices or costs.

Thermal Barrier

a material applied over polyurethane foam designed to slow the temperature rise of the foam during a fire and delay its involvement in the fire. Thermal barriers for use with SPF must have a time rating of not less than 15 minutes.

Thermal block

a compression-resistant insulation block installed between structural steel and the panels and their supporting members to help maintain insulation R-values and reduce condensation.

Thermal bridge

the penetration of a material of high thermal conductivity (e.g., a metal insulation or roof membrane fastener) through a material of low thermal conductivity (e.g., thermal insulation); the result is a lowered thermal resistance for the assembly.

Thermal conductance ©

the time rate of heat flow through a unit area of a body induced by a unit temperature difference between bodies. In English (inch.pound) units of measurement, the number of BTUs that pass through a specified thickness of a one square foot (0.09 m2) sample of material in one hour with a temperature difference between the two surfaces of 1 degree F. In English (inch.pound) units it is expressed as Btu/h.ft2.f. Note 1: A thermal conductance (C) value applies to a specific thickness of a specific material. Note 2: It is mathematically incorrect to multiply or divide the thermal conductance (C) value for a specific thickness of a material to determine the thermal conductance value of a different thickness of the same material. Note 3: It is mathematically incorrect to add thermal conductance (C) values to determine overall thermal performance. If it is necessary to determine the overall thermal performance of a construction, it is appropriate to convert the individual thermal conductance (C) values to thermal resistance (R) values (i.e., R=1/c, and then add the thermal resistance values (i.e., RT-R1, + R2 + ...).

Thermal conductivity (k)

the time rate of heat flow through a unit area of a homogeneous material in a direction perpendicular to isothermal planes induced by a unit temperature gradient is called thermal conductivity (k or k-value). In English (inch-pound) units of measurement, it is the number of BTUs that pass through a 1 inch (25 mm) thickness of a 1 square foot (0.09 m2) sample of material in one hour with a temperature difference between the two surfaces of 1 degree F. In English (inch-pound) units it is expressed as Btu.inch/ F. Note 1: A thermal conductivity (k) value applies to 1 inch (25 mm) thickness of a specific material. Note 2: It is mathematically incorrect to add, multiply, or divide the thermal conductivity (k) value of a material to determine the thermal performance value of a different thickness of the same material. If it is necessary to determine the thermal performance of a specific thickness of a material, it is appropriate to convert the thermal conductivity (k) of the material to a thermal resistance (R) value (i.e., R = 1/k), and then perform the mathematical calculation.

Thermal cycling

sequence of values by a repetitive temperature differential due to changes in radiant energy.

Thermal expansion

the increase in the dimension or volume of a body due to temperature variations.

Thermal Image

a visual representation of temperature distribution over a surface area. The image is displayed on a screen, presenting the response to infrared light waves.

Thermal insulation

a material applied to reduce the flow of heat.

Thermal movement

changes in dimension of a material as a result of temperature changes.

Thermal resistance (R)

under steady conditions, thermal resistance is the mean temperature difference between two defined surfaces of material or construction that induces unit heat flow through a unit area. In English (inch.pound) units it is expressed as degree F.ft2.h/Btu. Note 1: A thermal resistance (R) value applies to a specific thickness of a material or construction. Note 2: The thermal resistance (R) of a material is the reciprocal of the thermal conductance (C) of the same material (i.e., R = 1/C). Note 3: Thermal resistance (R) values can be added, subtracted, multiplied, and divided by mathematically appropriate methods.

Thermal shock

the stress-producing phenomenon resulting from sudden temperature changes in a roof membrane when, for example, a cold rain shower follows brilliant sunshine.

Thermal stress

stress introduced by uniform or non-uniform temperature change in a structure or material that is contained against expansion or contraction.

Thermal transmittance (U or U-factor)

thermal transmittance (U or U-factor) is the time rate of heat flow per unit area under steady conditions from the fluid (e.g., air) on the warm side of a barrier to the fluid (e.g., air) on the cold side, per unit temperature difference between the fluids. In English (inch.pound) units expressed as Btu/ F. Note 1: A thermal temperature transmittance (U) value applies to the overall thermal performance of a system (e.g., roof assembly). Note 2: Thermal transmittance (U) is sometimes called the overall coefficient of heat transfer. Note 3: Thermal transmittance (U) is reciprocal of the overall thermal resistance (RT) of a system (i.e., U = 1/RT).


a visible light record of the display of an infrared camera system via a Polaroid print, 35mm film, video tape, or computer generated image.

Thermography, Infrared

see Infrared thermography.


a material that softens when heated and hardens when cooled. This process can be repeated provided that the material is not heated above the point at which decomposition occurs.

Thermoplastic olefin membrane (TPO)

a blend of polypropylene and ethylene-propylene polymers. Colorant, flame retardants, UV absorbers, and other proprietary substances which may be blended with the TPO to achieve the desired physical properties. The membrane may or may not be reinforced.


a class of polymers that, when cured using heat, chemical, or other means, changes into a substantially infusible and insoluble material.


(1) a volatile liquid added to an adhesive or coating material to modify the consistency or other properties; (2) a liquid used to clean equipment or other surfaces.


the property of a material that enables it to stiffen in a relatively short time on standing, but6 upon agitation or manipulation to change to a very soft consistency or to a fluid of high viscosity, the process being completely reversible.

Thread Count

the number of threads per inch in each direction, with the warp mentioned first, and the fill second, (e.g., a thread count of 20 x 10 means 20 threads per inch [25.4mm] in the warp and 10 threads per inch [25.4mm] in the fill direction).

Through-wall flashing

a water-resistant membrane or material assembly extending totally through a wall and its cavities, positioned to direct water within the wall to the exterior, usually through weep holes.


in roofing and waterproofing, the transitional seal used to terminate a roofing or waterproofing application at the top or bottom of flashings or by forming a watertight seal with the substrate, membrane, or adjacent roofing or waterproofing system.


(in roofing and waterproofing) the transitional seal used to terminate a roofing or waterproofing application at the top or bottom of flashings, or by forming a watertight seal with the substrate, membrane or adjacent roofing or waterproofing system.


Thermal Insulation Manufacturers Association

Toggle bolt

a bolt having a nut with pivoted, flanged wings that close against a spring when it is pushed through a hole, and open after emerging from the hole; used to fasten objects to a hollow wall or to a wall which is accessible only from one side.

Tongue and groove planks

one of the oldest types of dimensional structural wood used as roof decking. The sides are cut with convex and concave grooves so adjacent planks may join in alignment with each other to form a uniform roof deck.


method used in the installation of polymer modified bitumen membranes characterized by using open flame propane torch equipment.


Tri-Polymer Alloy.


thermoplastic olefin.

Traffic bearing

in waterproofing, a membrane formulated to withstand a predetermined amount of pedestrian or vehicular traffic with separate protection and a wear course.

Transverse seam

the joint between the top of one metal roof panel and the bottom of the next panel, which runs perpendicular to the roof slope.

Treebark surface texture

in SPF roofing, the surface condition of the foam which shows a coarse texture where valleys form sharp angles. This surface is unacceptable for proper coating and protection.


the process of removing deteriorated mortar from an existing masonry joint and troweling new mortar or other filler into the joint.

Two-Part System

a coating of SPF formed by the mixing and (usually) the reaction of two different materials.

Warm roof assembly

a roof assembly configured with each component placed immediately on top of the preceding component; each component is in contact with the adjacent component. No space is provided for ventilation of the roof assembly. Also known as a "compact" roof assembly.

Wash coat

a primer, typically provided on the back side of painted metal products to help protect the underlying metal from wear and corrosion.

Water Absorption

the amount of water absorbed by a material after immersion for a prescribed period of time. May be expressed as a percentage of the original weight of the material.

Water cure

a method of curing a material, such as concrete, by applying a fine mist of water over the surface to control the rate of moisture evaporation from the material.

Water cutoff

see Cutoff.

Water stop

a diaphragm used across a joint as a sealant, usually to prevent the passage of water.

Water table

the level within the ground, below which the soil is saturated with water.

Water vapor transmission

a measure of the rate of transmission of water vapor through a material under controlled laboratory conditions of temperature and humidity. Customary units are grains/hòft2.


the ability of individual, overlapping components to resist the passage of water without hydrostatic pressure.


the quality of a membrane, membrane material, or other component to prevent water entry.


treatment of a surface or structure to prevent the passage of water under hydrostatic pressure.

Wear course

the top layer of surfacing that carries pedestrian or vehicular traffic. Sometimes referred to as wearing surface.

Wearing surface

see Wear course.

Weather Infiltration

the negative condition where rain or snow penetrate the roof. The condition is typically wind-driven.


an instrument used to subject material specimens to accelerated weathering conditions.


the ability of a membrane or roof covering to prevent the passage of water with a limited amount of hydrostatic pressure.

Weep holes

small openings whose purpose is to permit drainage of water that accumulates inside a building component (e.g., a brick wall, skylight frame, etc.).


to join pieces of metal together by heat fusion.


a condition where free water is present in a substance.

Wet bulb temperature

the temperature of air as registered by a thermometer whose bulb is covered by a water wetted wick.

Wet film thickness

the thickness, expressed in mils, of a coating or mastic as applied but not cured. For comparison, see Dry film thickness.


the process of moisture movement by capillary action.

Wind clip

a steep-slope roofing attachment device that fits over the butt end of tile, slate and stone to help secure individual roofing units from wind uplift.

Wind load

force exerted by the wind on a structure or part of a structure.

Wind uplift

the force caused by the deflection of wind at roof edges, roof peaks or obstructions, causing a drop in air pressure immediately above the roof surface.


being in or facing the direction toward which the wind is blowing. The side exposed to the prevailing wind.

Wire Tie System

a scheme of attachment for steep-slope roofing units (e.g., tile, slate, and stone) utilizing fasteners (nails and/or screws) in conjunction with wire to make up a concealed fastening system.

Wire tie system

a system of attachment for steep-slope roofing units (e.g., tile, slate and stone) using fasteners (nails and/or screws) in conjunction with wire to provide a concealed fastening system.

Work slab

see Mud slab.

Woven valley

a method of valley construction in which shingles or roofing from both sides of the valley extend across the valley and are woven together by overlapping alternate courses as they are applied.


a masonry wall, one masonry unit, a minimum of two inches thick.