Acrylic Coating: A type of coating that has an acrylic resin base.
Aggregate: A surfacing or ballast for a roof system. Aggregate can be rock, stone, crushed stone or slag, water-worn gravel, crushed lava rock or marble chips.
Air Blown Asphalt: Asphalt produced by blowing air through molten asphalt held at an elevated temperature. This procedure is used to modify properties of the asphalt.
Alligatoring: The cracking of the surfacing bitumen on a built-up roof, producing a pattern of cracks that resemble an alligator’s hide.
APP: See Atactic Polypropylene.
Application Rate: The rate at which a material is applied per unit of area, such as gallons per square.
Architectural Shingle: A type of asphalt shingle whose raised profile mimics the random shadows and patterns of slate, wood shingles or tile. See also Dimensional Shingle.
ASHRAE: American Society of Heating, Refrigerating & Air-Conditioning Engineers, Inc.
Asphalt: A brownish-black solid or semisolid mixture of bitumens obtained from native deposits or as a petroleum byproduct, which is typically used in paving, roofing and waterproofing. Asphalt can be refined to conform to various roofing grade specifications:
Type I (Dead-Level) Asphalt: A roofing asphalt for use in roofs which do not exceed a ¼ in 12 slope (2%).
Type II (Flat) Asphalt: A roofing asphalt for use in roofs which do not exceed a ½ in 12 slope (4%).
Type III (Steep) Asphalt: A roofing asphalt for use in roofs which do not exceed a 3 in 12 slope (25%).
Type IV (Special Steep) Asphalt: A roofing asphalt for use in roofs which do not exceed a 6 in 12 slope (50%).
Asphalt Emulsion: A mixture of asphalt particles and an emulsifying agent such as bentonite clay and water.
Asphalt Felt: An asphalt-saturated and/or an asphalt-coated roofing felt. (See also Felt.)
ASTM: American Society for Testing and Materials.
Atactic Polypropylene (APP): The polymer that is added to asphalt in APP modified bitumen roofing that gives the material greater elasticity.
Back-Nailing: The method of fastening the back or upper side of a ply of roofing felt or other component in a roof system so that the fasteners are covered by the following ply.
Ballast: A material installed over the top of a roof membrane to help hold it in place, such as aggregate or concrete pavers.
Base Flashing: Plies of roof membrane material used to seal a roof at vertical plane intersections, such as roof-wall and roof-curb junctures. (See also Flashing.)
Base Ply: The primary ply of roofing material in a roof system.
Base Sheet: An asphalt-impregnated or coated felt used as the first ply in some built-up and modified bitumen roof systems.
Batten: A strip of wood fastened to the structural deck or rafters for use in attaching a primary roof system, such as tile.
Bird Bath: A small, inconsequential amount of water that may accumulate on a roof, but quickly evaporates.
Bird Screen: Wire mesh installed over vents or other openings to prevent birds from entering a building or roof cavity.
Bitumen: Any of various flammable mixtures of hydrocarbons and other substances, whether occurring naturally or obtained by distillation from coal or petroleum, that are a component of asphalt and are used for roofing and waterproofing, as well as for surfacing roads.
Blind-Nailing: The use of nails so that they are not exposed to the weather in the finished roofing system. See Back-Nailing
Blister: A pocket of air or water vapor trapped between layers of roofing felt or membrane.
Blocking: Pieces of wood that are built into a roof assembly to stiffen the deck around an opening, support a curb, or to serve as nailers for the attachment of membranes or flashings.
Blown Asphalt: See Air Blown Asphalt.
Blueberry: A small bubble found in the flood coat of an aggregate-surfaced built-up roof. See also Tar Boil.
Boot: A piece of preformed material designed to protect roof penetrations from dirt, moisture and other foreign and/or damaging substances.
Brooming: Embedding a ply of roofing material into hot bitumen or adhesive by using a broom, squeegee, or other piece of equipment to eliminate voids and help ensure adhesion.
Built-Up Roof: A roof membrane consisting of layers of bitumen, which serves as the waterproofing component, with plies of reinforcement fabric installed between each layer. The reinforcement material can consist of bitumen-saturated felt, coated felt, polyester felt or other fabrics. A surfacing is generally applied to complete the roof system. Common surfacings include asphalt, aggregate, emulsion and granule-surfaced cap sheets.
Bundle: An individual package of shingles or shakes.
BUR: An acronym for Built-Up Roof.
Butt Joint: Where two separate, adjacent pieces of material abut.
Cant Strip: A triangular-shaped strip of material used to ease the transition from a horizontal plane to a vertical plane. Cant strips can be made of wood, wood fiber, perlite or other materials.
Cap Flashing: A material used to cover the top edge of base flashings or other flashings. (See also Coping.)
Cap Sheet: A granule-surfaced membrane often used as the top ply of BUR or modified bitumen roof systems.
Caulk: A material with no elastomeric properties that is used for sealing joints.
Caulking: The act of sealing a joint.
Cellulose: A complex carbohydrate that is the main constituent of the cell wall in most plants, and is used in the manufacturing of organic roofing materials.
Chopped Glass and Emulsion (CG&E): A roof coating that consists of asphalt or clay emulsion and glass fiber reinforcement.
Cladding: A material used to cover the exterior wall of a building.
Cleat: A continuous metal strip used to secure two or more metal roof components together.
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 installed over the top of those and then trimmed back from the valley centerline.
Coal Tar Pitch: A type of coal tar used in dead-level or low-slope built-up roofs. Because of its tight molecular structure, coal tar pitch is very resistant to corrosive environments and virtually impervious to standing water.
Coated Base Sheet: An asphalt-saturated base sheet membrane that is later coated with harder, more viscous asphalt, thereby increasing its impermeability to moisture.
Coated Felt: An asphalt-saturated ply sheet that has also been coated on both sides with harder, more viscous asphalt.
Cold Process Built-Up Roof: A roof consisting of multiple plies of roof felts laminated together with adhesives that do not require heating.
Composition Shingle: A type of asphalt shingle used in steep-slope roofing and generally comprised of weathering-grade asphalt, a fiber glass reinforcing mat, an adhesive strip, and mineral granules.
Concealed-Nail Method: A method of installing asphalt roll roofing material in which all nails or fasteners are driven into the underlying roofing and then covered by an overlapping course.
Cool Roof: A roofing material certified by the Cool Roof Rating Council as having a minimum solar reflectance of at least 0.70 and a minimum thermal emittance 0.75. The use of a “cool” roofing material can increase a building’s energy efficiency by reducing the surface temperature of the roof, which in turn reduces the air conditioning load on the building.
Coping: A piece of material used to cover the top of a wall and protect it from the elements. Copings can be constructed from metal, masonry or stone.
Counter Batten: Wood strips installed vertically on sloped roofs over which horizontal battens are secured.
Counterflashing: Formed metal sheeting secured to walls, curbs, or other surfaces, for use in protecting the top edge of base flashings from exposure to weather.
Course: The term used for each row of roofing material that forms the roofing or flashing system.
Crack: A separation or fracture occurring in a material. See also Split.
Creep: Movement of the roof membrane that can cause the roof system to deform.
Cricket: A roof component used to divert water away from curbs, platforms, chimneys, walls or other roof penetrations and projections. See also Saddle.
Curb: A raised member used to support skylights, HVAC units, exhaust fans, hatches or other pieces of mechanical equipment mounted above the level of the roof surface. A curb should usually be a minimum of eight inches (8") in height.
Cutback: Bitumen thinned by solvents that is used in cold-process roofing adhesives, roof cements, and roof coatings.
Cutout: The open area between shingle tabs.
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