Acid Etch: (1) The use of a strong acid to remove the surface of concrete thereby exposing the aggregate. (2) The use of a strong acid to etch the surface of material such as metal in order for that material to accept a primer or Spray Polyurethane Foam.
Acrylic Coating: A coating system with an acrylic resin base.
Acrylic Resin: Polymers of acrylic or methacrylic monomers often used as a latex base for coating systems.
Active: Will corrode in the presence of moisture or a “noble” metal.
Aggregate: A surfacing or ballast for a roof system. Aggregate can be rock, stone, crushed stone or slag, waterworn 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.
Aluminized Steel: Sheet steel with a thin aluminum coating on the surface to enhance the steel’s ability to withstand weathering.
Aluminum: A non-rusting metal used in roofing for metal roofing and the fabrication of gutter and flashings.
Anodic: When two metals are connected in an electrolyte, they will form a galvanic cell, with the higher metal in the galvanic series being the anode. The anodic will oxidize and produce an electrical current which protects the cathode from corrosion.
Apron Flashing: A flashing located at the low end of a curb or penetration.
Architectural Panel: A metal roof panel that usually requires solid decking underneath.
Architectural Shingle: Shingle that provides a dimensional appearance. See also Dimensional Shingle.
Area Divider: A flashed assembly usually extending above the surface of the roof that is anchored to the roof deck. It is used to relieve thermal stresses in a roof system where an expansion joint is not required, or to separate large roof areas.
ARMA: Asphalt Roofing Manufacturers Association
Asbestos: An incombustible fibrous mineral form of magnesium silicate formerly used for fireproofing and sometimes used for the reinforcement of roofing materials.
Asphalt: A substance left as a residue after evaporating or otherwise processing crude oil or petroleum.
Asphalt can be 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. This asphalt is for use in roofs which do not exceed a ¼ in 12 slope (2%).
Flat Asphalt: A roofing asphalt conforming to the requirements of ASTM Specification D 312, Type II. This asphalt is for use in roofs which do not exceed a ½ in 12 slope (4%).
Steep Asphalt: A roofing asphalt conforming to the requirements of ASTM Specification D 312, Type III. This asphalt is for use in roofs which do not exceed a 3 in 12 slope (25%).
Special Steep Asphalt: A roofing asphalt conforming to the requirements of ASTM Specification D 312, Type IV. This asphalt is 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 felt membrane.
Asphalt Roof Cement: The proper name for Plastic Cement and Flashing Cement. Asphalt roof cement consists of solventbased bitumen, mineral stabilizers, and other fibers (sometimes asbestos). Asphalt roof cement is categorized by ASTM standard D 2822-91 (1997) or for non-asbestos, ASTM standard D 4586-93. Plastic Cement is for use on low-slope surfaces, conforms to ASTM Specification D 312, Type I; Specification D 449, Types I or II; or Specification D 946. Plastic Cement is self-sealing, adhesive and ductile and is classified by ASTM Standard D 2822-91 Asphalt Roof Cement, and D 4586-92 Asphalt Roof Cement, Asbestos-Free, Types I and II. Flashing Cement can be used on vertical surfaces and has a high softening point, low ductility and conforms to the requirement of ASTM Specification D 312, Types II or III; or Specification D 449, Type III.
Atactic Polypropylene: A group of high molecular weight polymers formed by the polymerization of propylene.
Attic: The open area above the ceiling and under the roof deck of a steep-sloped roof.
