ROOFING GLOSSARY
This glossary contains many useful terms and definitions. You can browse the entire glossary by our alphabetical listing located on the right.
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.
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.
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.
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.
Application Rate
The quantity (mass, volume, or thickness) of material applied per unit area.
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.)
Asbestos
A group of natural, fibrous, impure silicate materials used to reinforce some roofing products.
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 III. 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 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 II. 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 I; Specification D 449, Types I or II; 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 III; or Specification D 449, Type III. (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
