Roofing Terms, Words and Definitions

Roofing Terms, Words and Definitions


Common Roofing Terms Defined & Explained Roofing Terms Glossary Definitions
The following is a list of terms or phrases commonly used in the roofing industry. Each term is accompanied by a brief definition.

Ambient Temperature: the temperature of the air; air temperature.
Architectural Shingle: shingle that provides a dimensional appearance.

Back-Nailing: (also referred to as Blind-Nailing) the practice of 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.
Base Ply: the lowermost ply of roofing in a roof membrane or roof system.
Base Sheet: an impregnated, saturated, or coated felt placed as the first ply in some multi-ply built-up and modified bitumen roof membranes.
Batten: (1) cap or cover; (2) in a metal roof: a metal closure set over, or covering the joint between, adjacent metal panels; (3) 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 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.
Bitumen: (1) a class of amorphous, black or dark colored, (solid, semi-solid, or viscous) cementitious sub-stances, natural or manufactured, composed principally of high molecular weight hydrocarbons, soluble in carbon disulfide, and found in petroleum asphalts, coal tars and pitches, wood tars and asphalts; (2) a generic term used to denote any material composed principally of bitumen, typically asphalt or coal tar.
Blackberry (sometimes referred to as Blueberry or Tar-Boil): a small bubble or blister in the flood coating of an aggregate-surfaced built-up roof membrane.
Blister: an enclosed pocket of air, which may be mixed with water or solvent vapor, trapped between imper-meable layers of felt or membrane, or between the membrane and substrate.
BOMA: Building Owners & Managers Association
Brake: hand- or power-activated machinery used to form metal.
British Thermal Unit (BTU): the heat energy required to raise the temperature of one pound of water one degree Fahrenheit (joule).
Brooming: an action carried out to facilitate embedment of a ply of roofing material into hot bitumen by using a broom, squeegee, or special implement to smooth out the ply and ensure contact with the bitumen or adhe-sive under the ply.
Building Code: published regulations and ordinances established by a recognized agency prescribing design loads, procedures, and construction details for structures. Usually applying to designated jurisdictions (city, county, state, etc.). Building codes control design, construction, and quality of materials, use and occupancy, location and maintenance of buildings and structures within the area for which the code has been adopted.
Bundle: an individual package of shakes or shingles.
Butyl: rubber-like material produced by copolymerizing isobutylene with a small amount of isoprene. Butyl may be manufactured in sheets, or blended with other elastomeric materials to make sealants and adhesives.
Butyl Coating: an elastomeric coating system derived from polymerized isobutylene. Butyl coatings are char-acterized by low water vapor permeability.
Butyl Rubber: a synthetic elastomer based on isobutylene and a minor amount of isoprene. It is vulcanizable and features low permeability to gases and water vapor.
Butyl Tape: a sealant tape sometimes used between metal roof panel seams and end laps; also used to seal other types of sheet metal joints, and in various sealant applications.

Canopy: any overhanging or projecting roof structure, typically over entrances or doors. Sometimes the extreme end is unsupported.
Cant: a beveling of foam at a right angle joint for strength and water run off.
Cap Flashing: usually composed of metal, used to cover or shield the upper edges of the membrane base flashing, wall flashing, or primary flashing. (See Flashing and Coping.)
Cap Sheet: a granule-surface coated sheet used as the top ply of some built-up or modified bitumen roof membranes and/or flashing.
Capillary Action: the action that causes movement of liquids by surface tension when in contact with two adjacent surfaces such as panel side laps.
CCF: 100 cubic feet.
Chalk: a powdery residue on the surface of a material.
Chalk Line: a line made on the roof by snapping a taut string or cord dusted with colored chalk. Used for alignment purposes.
Chalking: the degradation or migration of an ingredient, in paints, coatings, or other materials.
Chimney: stone, masonry, prefabricated metal, or a wood framed structure, containing one or more flues, projecting through and above the roof.
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 (51mm) from the valley centerline.
Coal Tar: a dark brown to black colored, semi-solid hydrocarbon obtained as residue from the partial evapo-ration or distillation of coal tars. 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 waterproof-ing agent in dead-level or low-slope built-up roof membranes, conforming to ASTM D 450, Type III.
Coal Tar Pitch: a coal tar used as the waterproofing agent in dead-level or low-slope built-up roof mem-branes, conforming to ASTM Specification D 450, Type I or Type III.
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.
Coated Base Sheet: a felt that has previously been saturated (filled or impregnated) with asphalt and later coated with harder, more viscous asphalt, which greatly increases its impermeability to moisture.
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-saturated felt that has also been coated on both sides with harder, more viscous “coating” asphalt; (2) a glass fiber felt that has been simultaneously impregnated and coated with asphalt on both sides.
Coating: a layer of material spread over a surface for protection or decoration. Coatings for SPF are generally liquids, semi-liquids, or mastics; spray, roller, or brush applied; and cured to an elastomeric consistency.
Cohesion: the degree of internal bonding of one substance to itself.
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.
Combustible: capable of burning.
Composition Shingle: a unit of asphalt shingle roofing.
Concealed-Nail Method: a method of asphalt roll roofing application in which all nails are driven into the underlying course of roofing and covered by an adhered, overlapping course.
Condensation: the conversion of water vapor or other gas to liquid state as the temperature drops or atmos-pheric pressure rises. (Also see Dew Point.)
Conductor Head: a transition component between a through-wall scupper and downspout to collect and direct run-off water.
Copper: a natural weathering metal used in metal roofing; typically used in 16 or 20 ounce per square foot thickness (4.87 or 6.10 kg/sq m).
Cornice: the decorative horizontal molding or projected roof overhang.
Course: (1) the term used for each row of shingles 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 each layer of roof cement).
Coverage: the surface area covered by a specific quantity of a particular material.
Cure Time: the time required to effect curing. The time required for a material to reach its desirable long-term physical characteristics.
Cutoff: a permanent detail designed to seal and 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-off, which may be a temporary or permanent seal.) (See Tie-Off.)

Dead Level: essentially horizontal or flat, as in a roof deck or rooftop with no intentional slope to the roof drains. Also referred to as zero (0) slope.
Dew Point Temperature: the temperature at which water vapor condenses in cooling air at the existing atmospheric pressure and vapor content. Cooling at or below the dew point will cause condensation.
Dome: a roof that is shaped like a half-circle, or a variation of one.
Dormer: a framed projection through the sloping plane of a roof.
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: a standing seam that utilizes a double, overlapping interlock between two seam panels. (See Standing Seam.)
Downspout: a 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.
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. A drip edge also can be used to break the continuity of contact between the roof perimeter and wall components to help prevent capillary action.
Dynamic Load: any load which is non-static, such as a wind load or a moving live load.

Eave: a projecting edge of a roof that extends beyond the supporting wall.
Efflorescence: the formulation of crystalline deposits, generally whitish in color, on the surface of stone, brick, concrete, or other masonry surface when moisture moves through and evaporates on the masonry. May also be caused by free alkalies leached from mortar, grout, or adjacent concrete.
Elastomeric Coating: a coating system which, when fully cured, is capable of being stretched at least twice its original length (100% elongation) and recovering to its original dimensions.
Exposure: (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 (51mm) by the number of shingled plies; thus, the exposure of 36 inch (914mm) wide felt in a shingled, four-ply membrane should be approximately 8 1 Ú2 inches (216mm) (See Figure 8); (2) the dimension of sidewall or roofing covering that is not covered or overlapped by the upslope course of component. The typical exposure for a standard-size, 3-tab shingle is 5 inches (127mm), depending upon manufacturer specifications.
Extrusion: a manufacturing process which consists of forcing batched and formulated material (which may be molten) through an orifice called a “die.” The shape and dimensions of the orifice determine the shape and dimensions of the finished product. Extrusion is one method by which some single-ply roofing membranes are manufactured.

Factory Seam: a splice/seam made by the manufacturer during the assembly of sections of materials into large sheets.
Fading: any lightening of initial color.
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.
Fishmouth: (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.
Flaking: detachment of a uniform layer of a coating or surface material, usually related to internal movement, lack of adhesion, or passage of moisture.
Flashing Cement: as used by the roofing industry, an ASTM D 2822 Type II roof cement that is 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 indicates it is intended for use on vertical surfaces. (See Asphalt Roof Cement and Plastic Cement.)
Flood (Pour) Coat: the surfacing layer of bitumen into which surfacing aggregate is embedded on an aggregate-surfaced built-up roof. A flood coat is generally thicker and heavier than a glaze coat, and is applied at approximately 45-60 pounds per square (2-3 kilograms per meter).
Flood Test: the procedure where a controlled amount of water is temporarily retained over a horizontal surface to determine the effectiveness of the waterproofing.

Galvanic Action: an electrolytic reaction between dissimilar metals in the presence of an electrolyte.
Galvanize: to coat with zinc.
Galvanized Steel: steel coated with zinc for corrosion resistance.
Gambrel: a roof that has two pitches on each side.
Gravel: aggregate resulting from the natural erosion of rock.

Hem: the edge created by folding metal back on itself.
Hoist: a mechanical lifting device.
“Hot” or “Hot Stuff”: the roofer’s term for hot bitumen.
Humidity: the amount of moisture contained in the atmosphere. Generally expressed as percent relative humidity (the ratio of the amount of moisture [water vapor] actually present in the air, compared to the maxi-mum amount that the air could contain at the same temperature.)
HVAC: heating, ventilating, and air conditioning equipment.

Ignition Temperature: the minimum temperature to which a solid, liquid, or gas must be heated in order to initiate or cause self-sustained combustion independent of the heating element.
Impregnate: to coat, saturate, and/or surround the fibers of a reinforcing mat or fabric with an enveloping liquid material, (e.g., bitumen, elastomeric compound, etc.).
Infrared Thermography: a practice of roof system analysis where an infrared camera is used to measure the temperature differential of a roof surface to locate areas of underlying wet or moist insulation.
Interlocking Shingles: individual shingles that mechanically attach to each other to provide wind resistance.
Inverted Roof Membrane Assembly (IRMA TM): a patented, proprietary variation of the “Protected Membrane Roof Assembly” in which Styrofoam ® Brand Insulation and ballast are placed over the roof membrane. IRMA TM and Styrofoam ® are registered trademarks of the Dow Chemical Company.


Lap Cement: an asphalt-based roof cement formulated to adhere overlapping plies or asphalt roll roofing.
Lap Seam: occurs where overlapping materials are seamed, sealed, or otherwise bonded.
Latex: a colloidal dispersion of a polymer or elastomer in water which coagulates into a film upon evaporation of the water.
Lead: a soft workable metal used for miscellaneous flashings.
Loose-laid Membranes: membranes that are not attached to the substrate except at the perimeter of the roof and at penetrations. Typically, loose-laid membranes are held in place with ballast, such as water-worn stone, gravel, pavers, etc.

Mechanically-Fastened Membranes: generally used to describe membranes that have been attached at defined intervals to the substrate. Mechanical fastening may be performed with various fasteners and/or other mechanical devices, such as plates or battens.
Meter: unit of length measurement in the metric system, equal to 39.37 inches.
Mineral-Surfaced Roofing: roofing materials whose surface or top layer consists of mineral granules.
Mineral-Surfaced Sheet: a roofing sheet that is coated on one or both sides with asphalt and surfaced with mineral granules.
Miter: the joint produced by joining two diagonally cut pieces.
Modified Bitumen: (1) a bitumen modified through the inclusion of one or more polymers (e.g., atactic polypropylene, styrene butadiene styrene, etc.); (2) composite sheets consisting of a polymer modified bitumen often reinforced and sometimes surfaced with various types of mats, films, foils, and mineral granules.
Mopping: the application of hot bitumen, with a roofer’s hand mop or mechanical applicator, to the substrate or to the felts of a bituminous membrane.
Solid Mopping: a continuous mopping of a surface.
Sprinkle Mopping: a random mopping pattern in which heated bitumen beads are strewn onto the sub-strate with a brush or mop.

Night Seal (or Night Tie-Off): 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.
Nineteen-Inch Selvage (Double-Coverage or Split-Sheet): a prepared roofing sheet with a 17 inch (430mm) granule surfaced exposure and a non-granule surfaced 19 inch (485mm) selvage edge. This material is some-times referred to as SIS, double-coverage, or according to ASTM Standard D 371-89, Standard Specification for Asphalt Roll Roofing (Organic Felt) Surfaced with Mineral Granules, Wide Selvage.
Ninety-Pound: a prepared organic felt roll roofing with a granule surfacing that has a mass of approximately 90 pounds per 100 square feet, (4400 g/m 2 ).
NRCA: National Roofing Contractors Association.


Penetration: (1) any object passing through the roof; (2) the consistency (hardness) 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.
Perlite: an aggregate used in lightweight insulating concrete and in preformed perlitic insulation boards, formed by heating and expanding siliceous volcanic glass.
Pittsburgh Lock Seam: a method of interlocking metal, usually at a slope change.
Plastic Cement: a roofing industry generic term used to describe Type I asphalt roof cement that is a trowel-able mixture of solvent-based bitumen, mineral stabilizers, other fibers and/or fillers. Generally, intended for use on relatively low slopes — not vertical surfaces.
Pliability: the material property of being flexible or moldable.
PMR: Protected Membrane Roof.
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.
Puncture Resistance: extent to which a material is able to withstand the action of a sharp object without perforation.

Roll Roofing: smooth-surfaced or mineral-surfaced, coated, prepared felts.
Run: horizontal dimension of a slope.

Saddle: a relatively small raised substrate or structure constructed to channel or direct surface water to drains or off the roof. A saddle may be located between drains or in a valley, and is often constructed like a small hip roof or like a pyramid with a diamond-shaped base. (See Cricket.)
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 sur-face cap sheet) in order to obtain better adhesion of the overlapping sheet.
Shingle: (1) individual unit of prepared roofing material designed for installation with similar units in overlap-ping rows or courses on inclines normally exceeding 3:12 slope (25%); (2) to cover with shingles; (3) to apply any roofing material in succeeding overlapping rows or courses similar to shingles.
Side Lap: the continuous longitudinal overlap of neighboring like materials.
Skylight: a roof accessory, set over an opening in the roof, designed to admit light. Normally transparent, and mounted on a raised framed curb.
Slab-On-Grade: a horizontal placement of concrete placed directly over a prepared earth substrate.
Slope: the angle of incline, usually expressed as a ratio of rise to run, or as a percent.
Snow Guard: a series of devices attached to the roof in a pattern that attempts to hold snow in place, thus preventing sudden snow or ice slides from the roof.
Snow Load: a load imposed on buildings or other structures due to snowfall. (Categorized as live or environmental load.)
Soil Stack: a sanitation pipe that penetrates the roof; used to vent plumbing fixtures.
Spalling: a condition in which the outer layer or layers of masonry or concrete material begin to break off or flake away.
Square: 100 square feet (9.29 m 2 ) of roof area.
Stainless Steel: an alloy of steel that contains a high percentage of chromium. Also may contain nickel or copper. Generally, has very good resistance to corrosion.
Starter Sheets: (1) felt, ply sheet, or membrane strips that are made or cut to widths narrower than the standard width of the roll, used to start the shingling pattern at an edge of the roof; (2) particular width sheets designed for perimeters in some mechanically attached and fully adhered single-ply systems.

Tab: the exposed portion of strip shingles defined by cutouts.
Test Cut: a sample of the roof, which may contain all components or just the membrane, usually used to diagnose the condition of the existing membrane, evaluate the type and number of plies or number of membranes, or rates of application such as determine the weight of the average interply bitumen moppings.
Thermal Shock: the stress-producing phenomenon resulting from sudden temperature changes in a roof membrane when, for example, a cold rain shower follows brilliant hot sunshine, which may result in sudden cooling or rapid contraction of the membrane.
Tie-Off: (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.
Toggle Bolt: a two-piece assembly consisting of a threaded bolt and an expanding clip that can fit through a drilled hole. The clip can spring outward to provide anchorage from the blind side.


