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Aggregate: (1) crushed stone, crushed slag or water worn gravel used for surfacing a built-up roof; (2) any granular mineral material.
Alligatoring: the cracking of the surfacing bitumen on a built-up roof, producing a pattern of cracks similar to an alligators hide; the cracks may or may not extend through the surfacing bitumen.
Application Rate: the quantity (mass, volume or thickness) of material applied per unit area.
Area Divider: a raised double wood member attached to a properly flashed wood base plate that is anchored to the roof deck. It is used to relieve thermal stresses in a roof system where no expansion joints have been provided. (See NRCA Construction Details)
Asbestos: A group of natural, fibrous, impure silicate materials.
Asphalt: A dark brown to black cementitious material in which the predominating constituents are bitumens, which occur in nature or are obtained in petroleum processing.
Dead-Level Asphalt: A roofing asphalt conforming to the requirements of ASTM Specification D312, Type I.
Flat Asphalt: A roofing asphalt conforming to the requirements of ASTM Specification D312, Type II.
Steep Asphalt: A roofing asphalt conforming to the requirements of ASTM Specification D312, Type III.
Special Steep Asphalt: A roofing asphalt conforming to the requirements of ASTM Specification D312, Type IV.
Asphalt, Air Blown: an asphalt produced by blowing air through molten asphalt at an elevated temperature to raise its softening point and modify other properties.
Asphalt Felt: An asphalt-saturated felt or an asphalt coated felt.
Asphalt Mastic: A Mixture of asphaltic material and graded mineral aggregate that can be poured when heated but requires mechanical manipulation to apply when cool.
Asphalt, Steam Blown: an asphalt produced by blowing steam through molten asphalt to modify its properties.
Asphaltene: A high molecular weight hydrocarbon fraction precipitated from asphalt by a designated paraffinic naphtha solvent at a specified temperature and solvent-asphalt ratio.
NOTE Ð The asphaltene fraction should be identified by the temperature and solvent asphalt ratio used.
Backnailing: The practice of blind-nailing roofing felts to a substrate in addition to hot-mopping to prevent slippage. (See Blind Nailing)
Base Flashing: (See Flashing)
Base Ply: The lowermost ply of roofing material in a roof membrane assembly.
Base Sheet: A saturated or coated felt placed as the first ply in some multi-ply built-up roof membranes.
Bitumen: (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 asphalts, tars, pitches and asphaltites; (2) a generic term used to denote any material composed principally of bitumen.
Bituminous: containing or treated with bitumen. Examples: bituminous concrete, bituminous felts and fabrics, bituminous pavement.
Bituminous Emulsion: (1) A Suspension of minute globules of bituminous material in water or in an aqueous solution; (2) a suspension of minute globules of water or an aqueous solution in a liquid bituminous material (invert emulsion).
Bituminous Grout: A mixture of bituminous material and fine sand that will flow into place without mechanical manipulation when heated.
Blackberry: A small bubble or blister in the flood coating of a gravel-surfaced roof membrane.
Blind Nailing: The practice of nailing the back portion of a roofing ply in a manner that the fasteners are not exposed to the weather in the finished product.
Blister: An enclosed pocket of air mixed with water or solvent vapor, trapped between impermeable layers of felt, or between the felt and substrate.
Blocking: Wood built into a roofing system above the deck and below the membrane and flashing to stiffen the deck around an opening, act as a stop for insulation, or to serve as a nailer for attachment of the membrane or flashing.
Bond: The adhesive and cohesive forces holding two roofing components in intimate contact.
Brooming: Embedding a ply of roofing material by using a broom to smooth out the ply and ensure contact with the adhesive under the ply.
British Thermal Unit (Btu): The heat energy required to raise the teemperature of one pound of water one degree Fahrenheit.
Built-Up Roof Membrane: A continuous, semi-flexible roof membrane assembly, consisting of plies of saturated felts, coated felts, fabrics or mats between which alternate layers of bitumen are applied, generally surfaced with mineral aggregate, bituminous materials, or a granule-surfaced roofing sheet. (Abbreviation: BUR.)
Cant Strip: A beveled strip used under flashing to modify the angle at the point where the roofing or water proofing membrane meets any vertical element.
Cap Flashing: (See Flashing)
Capillarity: the action by which the surface of a liquid (where it is in contact with a solid) is elevated or depressed, depending upon the relative attraction of the molecules of the liquid for each other and for those of the solid.
Cap Sheet: A granule-surfaced coated sheet used as the top ply of a built-up roof membrane or flashing.
Caulking: A composition of vehicle and pigment, used at ambient temperatures for filling joints that remains plastic for an extended time after application.
Coal Tar: A dark brown to black, semi-solid hydrocarbon obtained as residue from the partial evaporation of distillation of coal tar.
Coal-Tar Pitch: A cola tar used as the waterproofing agent in dead-level or low slope built-up roof membrane, conforming to ASTM Specification D450, Type II
Coal-Tar Waterproofing Pitch: A Cola tar used as the dampproofing or waterproofing agent in below-grade structures, conforming to ASTM Specification D450, Type II.
Coal-Tar Bitumen: A coal tar used as the waterproofing agent in dead-level or low slope built-up roof membrane, conforming to ASTM D450, Type III.
Coal-Tar Felts: A felt that has been saturated with refined coal tar.
Coated Sheet Felt: (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.
Cold Processing Roofing: A continuous, semi-flexible roof membrane, consisting of plies of felts, mats or fabrics that are laminated on a roof with alternate layers of cold-applied roof cement and surfaced with a cold-applied coating.
Condensation: The conversation of water vapor or other gas to liquid as the temperature drops or the atmospheric pressure rises. (See Dew-Point)
Coping: The covering piece on top of a wall exposed to the weather, usually sloped to shed water.
Counterflashing: 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.
Course: (1) The term used for each application of material that forms the waterproofing system or the flashing; (2) one layer of a series of materials applied to a surface (i.e., a five-course wall flashing is composed of three applications of mastic with one ply of felt sandwiched between each layer of mastic).
Coverage: The surface are continuously covered by a specific quantity of a particular roofing material.
Crack: A separation or fracture occurring in a roof membrane or roof deck, generally caused by thermal induced stress or substrated movement.
Creep: The permanent deformation of a roofing material or roof system caused by the movement of the roof membrane that results from continuous thermal stress or loading.
Cricket: A relatively small, elevated area of a roof constructed to divert water around a chimney, curb or other projection.
Cutback: Solvent-thinned bitumen used in cold process roofing adhesives, flashing cements and roof coatings.
Cutoff: A detail designed to prevent lateral water movement into the insulation where the membrane terminates at the end of a dayÕs work, or used to isolate sections of the roofing system. It is usually removed before the continuation of the work.
Dampproofing: 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-Level Asphalt: (See Asphalt)
Dead Loads: Non-moving rooftop loads, such as mechanical equipment, air conditioning units, and the roof deck itself.
Deck: The structural surface to which the roofing or waterproofing system (including insulation) is applied.
Delamination: Separation of the plies in a roof membrane system or separation of laminated layers of insulation.
Dew Point: The temperature at which water vapor starts to condense in cooling air at the existing atmospheric pressure and vapor content.
Double-Pour: The process of applying two layers of aggregate and bitumen to a built-up roof.
Drain: A device that allows for the flow of water from a roof area. (See NRCA Construction Details)
Dropback: A reduction in the softening point of bitumen that occurs when bitumen is heated in the absence of air. (See Softening Point Drift)
Edge Sheets: Felt strips that are cut to widths narrower than the standard width of the full felt roll, used to start the felt shingling pattern at a roof edge.
Edge Stripping: Application of felt strips cut to narrower widths than the normal felt roll width to cover a joint between flashing and built-up roofing.
Edge Venting: The practice of providing regularly spaced protected opening along a roof perimeter to relieve moisture vapor pressure.
Elastomer: A macromolecular material that returns rapidly to its approximate initial dimensions and shape after substantial deformation by a weak stress and the subsequent release of that stress.
Elastomeric: A rubber like synthetic polymer that will stretch when pulled and will return quickly to its original shape when released.
Embedment: (1) The process of pressing a felt, aggregate, fabric, mat or panel uniformly and completely into hot bitumen or adhesive; (2) the process of pressing granules into coating in the manufacture of factory prepared roofing.
Emulsion: The intimate dispersion of an organic material and water achieved by using a chemical or clay emulsifying agent.
Envelope: 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 birumen seepage from the edge of the membrane.
Equilibrium Moisture: (1) The moisture content of a material stabilized at a given temperature and relative humidity, expressed as percent moisture by weight; (2) the typical moisture content of a material in any given geographical area.
Equiviscous Temperature (EVT): The temperature at which the viscosity is 75 centipoise for asphalt and 25 centipoise for coal tar products; the recommended temperature ply or minus 25 F at the time of application.
Expansion Joint: A structural separation between two building elements that allows free movement between the elements without damage to the roofing or waterproofing system.
Exposure: (1) The traverse dimension of a roofing element not overlapped by an adjacent element in any roof system. The exposure of any ply in a membrane may be computed by dividing the felt width minus 2 inches by the number of shingled plies; thus, the exposure of 36 inch wide felt in a shingled, four-ply membrane should be 8 * inches; (2) the time during which a portion of a roofing element is exposed to the weather.
Fabric: A woven cloth of organic or inorganic filaments, threads or yarns.
Factory Mutual (FM): An organization that classifies roof assemblies for their fire characteristics and wind uplift resistance for insurance companies in the United States.
Factory Square: 108 square feet of roofing material.
Fallback: (See Dropback)
Felt: A flexible sheet manufactured by the interlocking of fibers through a combination of mechanical work, moisture and heat. Felts are manufactured principally from vegetable fibers (organic felts), asbestos fibers (asbestos felts) or glass fibers (glass fiber felts); other fibers may be present in each type.
Felt Layer: A machine used for applying bitumen and built-up roofing felts.
Felt Mill Ream: The mass in pounds of 48- square feet or dry, unsaturated felt; also termed "point weight."
Fine Mineral Surfacing: Water Insoluble, inorganic material. More than 50 percent of which passes the No. 35 sieve, used on the surface of roofing.
Fishmouth: (1) A half-cylindrical or half-conical opening formed by an edge wrinkle; (2) in shingles, a half-conical opening formed at a cut edge.
Flashing: The system used to seal membrane edges at walls, expansion joints, drains, gravel stops, and other places where the membrane is interrupted or terminated. Base flashing covers the edge of the membrane. Cap flashing or counterflashing shields the upper edges of the base flashing.
Flashing Cement: A trowelable mixture of cutback bitumen and mineral stabilizers, including asbestos or other inorganic fibers.
Flat Asphalt: (See Asphalt)
Flood Coat: The top layer or bitumen into which the aggregate is embedded on an aggregate-surfaced built up roof.
Fluid Applied: An elastomeric material, fluid at ambient temperature, that dries or cures after application to form a continuous membrane. Such systems normally do not incorporate reinforcement.
Glass Felt: Glass fibers bonded into a sheet with resin and suitable for impregnation in the manufacture of bituminous waterproofing materials, roof membranes, and shingles.
Glass Mat: A thin mat composed of glass fibers with or without a binder.
Glaze Coat: (1) The top layer of asphalt in a smooth surfaced built-up roof assembly; (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.
Gravel: Course, granular aggregate, with pieces larger than sand grains, resulting from the natural erosion of rock.
Gravel Spot: A flanged device, frequently metallic, designed to provide a continuous finished edge for roofing material and to prevent loose aggregate from washing off the roof.
Headlap: The minimum distance, measured at 90 degrees to the eaves along the face of a shingle or felt, from the upper edge of the shingle or felt to the nearest exposed surface.
Holiday: An area where a liquid-applied material is missing.
"Hot Stuff" or "Hot": The roofer’s term for hot bitumen.
Hygroscopic: Attracting, absorbing and retaining atmospheric moisture.
Ice Dam: A mass of ice formed at the transition from a warm to a cold roof surface, frequently formed by refreezing meltwater at the oeverhang of a steep roof, causing ice and water to back up under roofing materials.
Incline: The slope of a roof expressed either in percent or in the number of vertical units of rise per horizontal unit of run.
Inorganic: Being or composed of matter other than hydrocarbons and their derivatives, or matter that is not of plant or animal origin.
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