(1) The ability of the membrane to resist mechanical abrasion such as foot traffic and wind-blown particles which tend to progressively remove materials from its surface; (2) 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.; (3) The ability of a membrane to resist being worn away by contact with a moving, abrasive surface, such as foot traffic.

(1) The ability of a material to accept within its body quantities of gases or liquid, such as moisture; (2) The ability of a porous solid material to hold within its body relatively large quantities of gases or liquid.

The proves 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 materials' 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.

American Concrete Institute

In waterproofing, use of a strong acid to cut away and remove the surface of concrete to expose the aggregate.

American Council of Independent Laboratories

Asbestos Containing Material

Metal deck panel perforated to absorb sound.

A group of thermoplastics formed by polymerizing esters of acrylic acid. Acrylic coatings are permeable and water-based, curing by evaporation. Colors are available.

Polymerization in which monomers are linked together without the splitting off of water or other molecules.

(1) 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; (2) To cause two surfaces to be held together by the combined strength of the molecular forces and the mechanical interlocking achieved between adhesive and the bonded surface.

(1) The ability of the membrane to remain adhered during its service life to the substrate or to itself; (2) The state in which two surfaces are held together by interfacial forces which may consist of molecular forces or interlocking action or both.

Failure of the bond between a compound and the surface with which it is in contact, allowing the compound to pull away and create an openings. See COHESIVE FAILURE.

A polyurethane rubber, strong, tough and abrasion-resistant.

The adhesion of an extremely thin layer of molecules (of gases or liquids) to the surface of solids or liquids with which they are in contact.

American Fiberboard Association

A three-piece rigid structural frame in the shape of the upright capital letter A. See FRAMING.

(1) Crushed stone, crushed slab or water-worn gravel used for surfacing or ballasting a built-up roof; (2) Any granular mineral material; (3) Gravel, crushed stone, slag, or mineral granules either (a) Embedded in a conventional built up membrane's bituminous flood coat, or (b) Applied to a loose laid roof system as a protective ballast; (4) Crushed stone, slag, or water-worn gravel used for surfacing a built-up roof; any granular mineral material.

Associated General Contractors of America

Rock, stone, crushed stone, crush slag, water worn gravel or marble chips used for surfacing and/or ballasting a roof system.

(1) The effect on materials that are exposed to an environment for an interval of time; (2) The process of exposing materials to an environment for an interval of time.

American Hardboard Association

American Institute of Architects

A device used to test, in the field, the integrity of field seams in plastic sheeting. It consists of a wand or tube through which compressed air is blown.

(As it Relates to Passive Ventilation): A negative conditions 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.

American Institute of Steel Construction

A type of roof discoloration caused by algae. Commonly called fungus growth.

(1) The cracking of the surfacing bitumen on a built-up roof, producing a pattern of cracks similar to an alligator's hide; the cracks or may not extend through the surfacing bitumen; (2) Deep shrinkage cracks, progressing down from the surface, in smooth surfaced membrane coatings and sometimes in bare spots of aggregate surfaced membranes. It is a consequence of photo oxidative hardening.

A mixture or blend of similar materials (thermoplastic) melted and re extruded into a new material from which the original materials cannot be separated.

Normally used as a topcoat, a material that contains a specific class of iscyanates based on a long, straight-chain molecular structure noted for its high tensile strength, high gloss, color-stable properties and ultraviolet resistance.

The capacity of water to neutralize acids, a property imparted by the water's content of carbonates, bicarbonates, hydroxides, and occasionally borates, silicates, and phosphates. It is expressed in milligrams of calcium carbonate equivalent per liter. This is one method of determining the amount of base in water.

The cracking of the surfacing bitumen asphalt which occurs curing the aging process in which the loss of volatile oils and the oxidation brought about by solar radiation; produces a pattern of cracks similar to an alligator's hide. The cracks may or may not extend through the surfacing bitumen.

Material that has metallic properties and which is composed of two or more elements, of which at least one element is a metal.

A chemical blend of two or more polymers, typically a rubber and a plastic to improve a given property (i.e., impact strength).

An electrical current in which the charge flow periodically reverses.

Silvery, lightweight, easily worked, metallic element that resists corrosion.

Surrounding air temperature.

A meter used to measure electrical current flow.

A steel bolt usually fixed in a building structure with its threaded portion projecting; used to secure frameworks, timbers, etc.

(A<F128M>É<F255D>) A unit of measurement equal to .0001 microns (.0000000001 meters). Generally used to measure the wavelength of certain types of electromagnetic radiations. For example, the red line of cadmium is defined as 6438 A<F128M> É<F255D>.

Term for metal treatment of modification.

Prevents corrosion of exposed areas of the base metal by galvanic protection. The coating provides a sacrificial anode and undergoes corrosion so that the base metal cathode is protected from further corrosion until all the nearby anode coating metal is gone.

A uniform annual amount equivalent to the project costs or benefits taking into account the time value of money throughout the sturdy period. (Syn: annual worth, equivalent uniform annual vale.)

Costs incurred in a regular pattern each year throughout the study period, normally for operation and maintenance (O & M).

A deviation beyond the range of normal variations.

American National Standards Institute

A compounding material used to retard deterioration caused by oxidation, ozone, light and combinations of these.

A substance that prevents or retards oxidation of material exposed to air.

Approval drawings may include framing drawings, elevations and sections through the building as furnished by the manufacturer for the approval of the buyer. Approval by the buyer affirms that the manufacturer has correctly interpreted the overall contract requirements for the system and its accessories, and the exact location of accessories in the building.

An avenue or passageway, roofed over and enclosed except at the ends; serving as a common entrance and egress for shops, stores and similar places of business located therein.

A person technically qualified and professionally licensed to practice architecture, the designing and administering the construction of buildings.

A drawing that shows the plan view and/or elevations of the finished building for the purpose of showing the general appearance of the building, indicating all accessory locations.

Requirements establishing criteria materials and methods used for a specific construction.

The art of science of building, including planning, designing, construction and decorative treatment.

(1) A raised, double wood member attached to a properly flashed wood base plate that is anchored to the roof deck. It is used to relieve thermal stresses of thermal expansion and contraction in a roof system where no expansion joints have been provided (See NRCA Construction Detail D-1); (2) 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).

A method of work or construction that is widely used in a geographical area and therefore sets the norm for that area.

Asphalt Roofing Manufacturers Association

A single or plural-component polyurethane coating that is a polymer-based on cyclical molecular structure. It is normally used as a base coat for aliphatic top coat systems and as a ultraviolet-retardant top coat.

American Subcontractors Association

(1) A group of natural, inorganic, fibrous, impure silicate materials; used to reinforce some roofing products.

Roofing felt reinforced with asbestos.

Associated Specialty Contractors

American Society of Civil Engineering

The incombustible material that remains after a substrate has been burned.

American Society of Home Inspectors

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

(1) A dark brown to black cementitious material, solid or semisolid, in which the predominating constituents are bitumens, which occur in nature (Trinidad asphalt) or are obtained in petroleum processing; (2) A similar material obtained from refining petroleum, used as a waterproofing agent; (3) Dark brown to black, highly viscous, hydrocarbon produced from the residuum left after the distillation of petroleum, used as the waterproofing agent of a built-up roof; (4) a bituminous waterproofing agent applied to roofing materials during manufacture; (5) 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. See DEAD LEVEL ASPHALT.

Flat Asphalt: A roofing asphalt conforming to the requirements of ASTM Specification D 312, Type II. See FLAT ASPHALT.

Steep Asphalt: A roofing asphalt conforming to the requirements of ASTM Specification D 312, Type III. See STEEP ASPHALT.

Special Steep Asphalt: A roofing asphalt conforming to the requirements of ASTM Specification D 312, Type IV. See SPECIAL STEEP ASPHALT.

An asphalt produced by blowing air through molten asphalt at an elevated temperature to raise its softening point and modify other properties.

(1) 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; (2) Asphalt which has been rendered liquid by the addition of water and an emulsifying agent. After application, the water evaporates leaving asphalt. (Cannot be sotred or used in freezing weather without damage to the product)..

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

An asphalt-saturated and/or an asphalt-coated felt. See FELT.

A mixture of asphaltic material and grade mineral aggregate that can be poured when heated but requires mechanical manipulation to apply when cool. See FLASHING CEMENT, MASTIC, PLASTIC CEMENT and ROOF CEMENT.

An asphalt based cement used to bond roofing materials. Also known as flashing cement or mastic; should conform to ASTM D 4586.

Asphalt tinned to a liquid by solvent, so that it may be brushed or spray-applied to surfaces to ensure adhesion of hot asphalt. See PRIMER.

A trowelable mixture of solvent-base bitumen, mineral stabilizers, other fibers and/or filler. Classified by ASTM D 2822 91 Asphalt Roof Cement, and D 4586-92 Asphalt Roof Cement, Asbestos Free, Types I and II.

(Type I): Generally referred to as "plastic cement", and is made from asphalt characterized as self-sealing, adhesive and ductile, and conforming to ASTM D 312, Type I; Specification D 449, Types I or II; or Specification D 946. See PLASTIC CEMENT AND FLASHING CEMENT.

(Type II): Generally referred to as "vertical-grade flashing cement" and is made form asphalt characterized by high softening point and relatively low ductility; and, and conforming to the requirements of ASTM Specification D 312, Types II or III; or Specification D 449, Type III. (See Plastic Cement and Flashing Cement.)

A device on wheels with nozzles that may be adjusted to control the flow of asphalt released as it is pulled over the roof.

An asphalt produced by blowing steam through molten asphalt to modify its properties, normally used for highway bitumen.

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

The American Society for Testing and Materials; a consensus standards setting organization; Philadelphia, PA. A voluntary organization concerned with development of consensus standards, testing procedures and specifications, and recognized for setting standards by which materials are judged.

A chain of molecules in which the position of the side methyl groups is more or less random (amorphic; low crystallinity).

(1) A group of high molecular weight polymers formed by the polymerization of propylene; (2) Amorphous polypropylene with a random arrangement; used in modified bitumens as a plastic additive to permit heat fusion (torching).

Defined by the number of protons in the nucleus of a chemical element.

The mass of the neutrons and protons in the nucleus of an atom of any given element.

(1) The main inner hall of a Roman house with an aperture in the roof for rainwater and a rectangular basin to receive the water; (2) The forecourt of an early Christian basilica.

Any space immediately under the roof rafters and above the ceiling joists of the story nearest the roof.

A welding operation utilizing a machine to make a uniform, high quality weld.

All specified dynamic line loads other than the basic design loads which a building must safely withstand; includes cranes, material-handling systems, machinery, elevators, vehicles and impact loads.

In statistics, the mean average is the sum/quantity of the values from a series of tests performed. The median average would be the middle value of a series of numbers. The mode would be the most common number of a set of numbers.

This is a broad category of fixed or movable rooflike structures including the following: cabana, roller curtain, canopy, canopy shutter and they may be rigid, folding, self-supporting or cantilevered.

American Wood Preservatives Association

American Welding Society