Glossary of Roofing and Waterproofing Terms

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: American Architectural Manufacturers Association

Abrasion Resistance: the ability of a material to resist being worn away by contact with another moving, abrasive surface, such as foot traffic, mechanical equipment, wind-blown particles, etc.

Absorption: the ability of a material to accept within its body quantities of gases or liquid, such as moisture.

Accelerated Weathering: the process in which materials are exposed to a controlled environment where various exposures such as heat, water, condensation, or light are altered to magnify their effects, thereby accelerating the weathering process. The material's physical properties are measured after this process and compared to the original properties of the unexposed material, or to the properties of the material that has been exposed to natural weathering.

ACI: American Concrete Institute

Acid Etch: in waterproofing, use of a strong acid to cut away and remove the surface of concrete to expose the aggregate.

ACIL: American Council of Independent Laboratories

Acrylic Coating: a coating system based on an acrylic resin. Generally, a latex-based coating system which cures by air drying.

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: to cause two surfaces to be held together by adhesion, typically with asphalt or roofing cements in built-up roofing and with contact cements in some single-ply membranes.

Adhesion: the state in which two surfaces are held together by interracial forces which may consist of molecular forces or interlocking action, or both.

AFA: American Fiberboard Association

AGO: Associated General Contractors of America

Aggregate: rock, stone, crushed stone, crushed slag, water-worn gravel or marble chips used for surfacing and/or ballasting a roof system.

Aging: the effect on materials that are exposed to an environment for an interval of time.

AHA: American Hardboard Association

AIA: American Institute of Architects

Air Leakage: (as it relates to passive ventilation) negative condition where air leaks into the roof cavity (designed for use as a passive ventilation system) through cracks or openings in the structure in lieu of through the intended intake vents.

Alligatoring: the cracking of the surfacing bitumen on a built-up roof, producing a pattern of cracks similar to an alligator's hide; the cracks may or may not extend through the surfacing bitumen.

Aluminized Steel: sheet steel with a thin aluminum coating bonded to the surface to enhance weathering characteristics.

Aluminum: a non-rusting metal sometimes used for metal roofing and flashing.

Ambient Temperature: the temperature of the air; air temperature.

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 oxidizes and produces an electrical current to protect the cathode from corrosion.

ANSI: American National Standards Institute

APA: American Plywood Association

APP: see Atactic Polypropylene.

Application Rate: the quantity (mass, volume, or thickness) of material applied per unit area.

Apron Flashing: a term used for a flashing located at the juncture of the top of the sloped roof and a vertical wall or steeper-sloped roof.

Architectural Panel: a metal roof panel, typically a double standing seam or batten seam; usually requires solid decking underneath and relies on slope to shed water.

Architectural Shingle: shingle that provides a dimensional appearance.

Area Divider: a raised, flashed assembly (typically a single- or double-wood member attached to a wood base plate) 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 (sometimes between expansion joints), and may be used to facilitate installation of tapered insulation. (See NRCA Construction Details.)

ARMA: Asphalt Roofing Manufacturers Association

ASA: American Subcontractors Association

Asbestos: a group of natural, fibrous, impure silicate materials used to reinforce some roofing products.

ASC: Associated Specialty Contractors

ASHI: American Society of Home Inspectors

ASHRAE: American Society of Heating, Refrigerating & Air-Conditioning Engineers, Inc.

Asphalt: a dark brown or black substance found in a natural state or, more commonly, left as a residue after evaporating or otherwise processing crude oil or petroleum. Asphalt may be further 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.
  • Flat Asphalt: a roofing asphalt conforming to the requirements of ASTM Specification D 312, Type II.
  • Steep Asphalt: a roofing asphalt conforming to the requirements of ASTM Specification D 312, Type lilt
  • Special Steep Asphalt: a roofing asphalt conforming to the requirements of ASTM Specification D 312, Type IV.

Asphalt, Air Blown: produced by blowing air through molten asphalt held at an elevated temperature, to raise the asphalt's softening point and modify other properties.

Asphalt Emulsion: a mixture of asphalt particles and an emulsifying agent such as bentonite clay and water. These components are combined by using a chemical or a clay emulsifying agent and mixing or blending machinery.

Asphalt Felt: an asphalt-saturated and/or an asphalt-coated felt. (See Felt.)

Asphalt Primer: see Primer.

Asphalt Roof Cement: a trowelable mixture of solvent-based bitumen, mineral stabilizers, other fibers and/or fillers. Classified by ASTM Standard D 2822-91 Asphalt Roof Cement, and D 4586-92 Asphalt Roof Cement, Asbestos-Free, Types I and 11

  • Type I is generally referred to as "plastic cement," and is made from asphalt characterized as self-sealing, adhesive and ductile, and conforming to ASTM Specification D 312, Type l; Specification D 449, Types I or Il; or Specification D 946. (See Plastic Cement and Flashing Cement.)
  • Type II is generally referred to as "vertical-grade flashing cement," and is made from asphalt characterized by a high softening point and relatively low ductility, and conforming to the requirement of ASTM Specification D 312, Types II or lil; or Specification D 449, Type lilt (See Plastic Cement and Flashing Cement.)

Asphaltene: a high molecular weight hydrocarbon fraction precipitated from asphalt by a designated solvent (paraffinic naphtha) at a specified temperature and solvent-asphalt ratio.

ASTM: American Society for Testing and Materials

Atactic Polypropylene: a group of high molecular weight polymers formed by the polymerization of propylene.

Attic: the cavity or open space above the ceiling and immediately under the roof deck of a steep-sloped roof.

AWPA: American Wood Preservatives Association

AWS: American Welding Society


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