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| Absorption | The act or process of retaining foreign particles such as gas or liquid without transmission of these particles. |
| Acid Etch | (1) The use of a strong acid to remove the surface of concrete thereby exposing the aggregate. <BR><BR>(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. |
| Adhere | The clinging of one surface to another; either molecularly or otherwise. |
| Adhesion | The state of adhering. |
| 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. |
| AHA | American Hardboard Association |
| AIA | American Institute of Architects |
| 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. |
| Ambient Temperature | The temperature of the air. |
| 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. |
| ANSI | American National Standards Institute |
| APA | American Plywood Association |
| APP | See Atactic Polypropylene. |
| Application Rate | The rate at which a material is applied per unit area. |
| 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 |
| ASA | American Subcontractors Association |
| Asbestos | An incombustible fibrous mineral form of magnesium silicate formerly used for fireproofing and sometimes used for the reinforcement of roofing materials. |
| ASC | Associated Specialty Contractors |
| ASHI | American Society of Home Inspectors |
| ASHRAE | American Society of Heating, Refrigerating & Air-Conditioning Engineers, Inc. |
| 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:<BR><BR>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%).<BR><BR>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%).<BR><BR>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%).<BR><BR>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. (See also Felt.) |
| Asphalt Primer | See Primer. |
| Asphalt Roof Cement | The proper name for Plastic Cement and Flashing Cement. Asphalt roof cement consists of solvent-based 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.<BR><BR>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. <BR><BR>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. |
| ASTM | American Society for Testing and Materials |
| 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. |
| AWPA | American Wood Preservatives Association |
| AWS | American Welding Society |