ACRYLIC COATING: A coating system with an acrylic resin base.

ADHERE: The bonding of one surface to another.

ADHESION: The state of adhering.

ALLIGATORING: Shrinkage cracking of the bituminous surface of built-up roofing, or the exposed surface of smooth-surfaced roofing, in which the loss of volatile oils and the oxidation pf compounds under solar radiation produces a pattern of deep cracks with the scaly look of an alligator’s hide. It occurs only in unsurfaced bitumen exposed to the weather.

ALUMINIZED STEEL: Sheet steel with a thin aluminum coating on the surface to enhance the corrosion resistance.

ALUMINUM: A non-ferrous metal used in roofing and fabrication of gutters and flashings. It is highly resistant to corrosion and lightweight.

ASBESTOS: An incombustible fibrous mineral form of magnesium silicate formerly used for fireproofing and sometimes used for the reinforcement of roofing materials.

ASPHALT: A dark brown to black, highly viscous, hydrocarbon produced from the residue left after the distillation of petroleum, used as the waterproofing agent of a built-up roof. It comes in a wide range of viscosities and softening points - from about 135ºF (dead level asphalt) to 210ºF or more (special steep asphalt.)

ASPHALT FELT: A reinforcing fabric membrane made by asphalt coating or saturating a paper, fiberglass, or polyester mat typically for use in a built-up roof system..

BASE FLASHING: Plies of roof membrane material used to seal a roof at the vertical plane intersections, such as at a roof-wall and roof-curb junctures.

BASE SHEET: A saturated and coated felt placed as the first ply in a multi-ply built-up roofing membrane.

BITUMEN: The generic term for an amorphous, semisolid mixture of complex hydrocarbons derived from petroleum or coal. In the roofing industry, there are two basic bitumens: asphalt and coal tar pitch. Before application, they are (1) heated to a liquid state, (2) dissolved in a solvent, or (3) emulsified.

BLISTER: A spongy, raised portion of a roofing membrane, ranging in size from 1” in diameter and barely detectable height to as much as 50 sq. ft. in area and 1 ft. high. Blisters result from the pressure of entrapped air or water vapor.

BUILT-UP ROOFING MEMBRANE: 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 and can be asphalt, aggregate, emulsion or a granule surfaced cap sheet.

BUR: Abbreviation sometimes used for built-up roofing membranes.

CANT STRIP: A continuous strip of triangular cross section, fitted into the angle formed by a roof deck and a wall or other vertical surface. The 45-degree slope of the exposed surface of the cant strip provides a gradual transition for base flashing and roofing membrane from a horizontal roof surface to a vertical surface.

CAP SHEET:  A mineral-surfaced coated felt used as the top ply of a built-up roofing system.

CAULK: The act of sealing a joint between two surfaces with an elastomeric compound.

COAL-TAR BITUMEN: A proprietary trade name for Type III coal tar used in dead-level or low-slope built-up roofs. It in not for use in roofs exceeding ¼” in 12” (2%) slope.

COAL-TAR PITCH:  A black solid hydrocarbon obtained from the residue of the distillation of coke-oven tar, used as the waterproofing agent of dead level or low slope built-up roofs. It comes in a narrow range of softening points - from 140º to 155ºF.

COLD-PROCESS ROOFING: A bituminous membrane comprising of layers of coated felts bonded with cold applied asphalt roof cement and surfaced with a cutback(solvent based) or emulsified asphalt roof coating.

CONDUCTER HEAD: A box-shaped sheet metal component used to direct water from a through-wall scupper to a downspout. Also known as a Collector Head.

COPING:  The piece of material used to cover the top of a wall and protect it from the elements. It can be constructed from metal, masonry, or stone.

CRICKET: A roof component used to divert water away from curbs, platforms, chimneys, walls, or other roof penetrations and projections.

CURB: A raised member used to support skylights, HVAC units, exhaust fans, hatches or other pieces of mechanical equipment above the level of the roof surface.

DELAMINATION: A built-up roofing membrane failure characterized by separation of the felt plies, sometimes resulting in wrinkling and cracking.

DOWNSPOUT: A conduit for carrying water from a gutter, scupper, drop outlet or other drainage unit from roof to ground level.

DRAIN: A device used to carry water off a roof.

ELASTOMERIC: Having elastic properties, capable of expanding or contracting with the surfaces to which the material is applied without rupturing.

EPDM: Ethylene Propylene Diene Monomer, a rubber compound used to produce roof membranes and many other products.

EXPANSION JOINT: A provision in design intended to allow movement to occur within a structure at a predetermined location.