Glossary: A


Abrasion ResistanceResistance to being worn away by rubbing or friction.
AbsorptionThe process by which a liquid or mixture of liquid and gases is drawn into the pores of a porous solid material.
AbsporptivityThe relative ability to absorb sound and light.
Abutment JointA surface divider joint designed to allow free movement between new and existing construction or between different materials.
AcceleratorA substance, such as calcium chloride, added to a concrete mix to speed up its setting and strength development.
Access FlooringA raised finish floor surface consisting entirely of small, individually removable panels beneath which wiring, ductwork, and other services may be installed.
Access RightRight of an owner to have ingress and egress to and from a property.
Accessory BuildingA building or structure on the same lot as the main or principal building.
Acoustical CeilingA ceiling of fibrous tiles that are highly absorbent of sound energy.
Acoustical GlassA glazing unit used to reduce the transmission of sound through the glazed opening by bonding a soft interlayer between the layers of glass.
Acoustical PlasterCalcined gypsum mixed with lightweight aggregates.
AcousticsScience dealing with the production, control, transmission, reception and effects of sound, and the process of hearing.
AcrylicA transparent thermoplastic made from esters of acrylic acid.
Active PressureThe pressure exerted by retained earth against a retaining wall.
AdditiveMaterials mixed with a basic plastic resin to alter its properties.
AdhesionThe ability of a coating to stick to another surface.
AdhesiveA substance used to hold materials together by surface attachment.
AdmixtureA prepared substance added to concrete to alter or achieve certain characteristics.
AdsorbantA material that has the ability to cause molecules of gases, liquids, or solids to adhere to its surfaces without changing the adsorbent physically or chemically.
AestheticsThe sudy or theory of beauty.
AgglomerationA process that bonds ground iron-ore particles into pellets to facilitate handling.
AggregateSand, gravel, crushed stone or other material that is a main constituent of Portland Cement, concrete and aggregated gypsum plaster. Also, polystyrene, perlite and vermiculite particles used in texture finishes.
AIA(1) The American Institute of Architects. Founded in 1857 and headquartered in Washington DC, the AIA offers resources for architects and is an advocate for the value of architecture.Architects also use the AIA designation to indicate that they are both members of The American Institute of Architects and licensed to practice the profession.(2) American Insurance Assn., successor to the National Board of Fire Underwriters and a nonprofit organization of insurance companies.
Air EntrainmentThe incorporation of tiny air bubbles into concrete or mortar to improve its workability and resistance to freezing.
Air GapIn plumbing, an unobstructed vertical distance between the lowest opening of any pipe that supplies a plumbing fixture and the level at which the fixture will overflow.
Air-ConditioningThe process of treating air to control simultaneously its humidity, cleanliness, and temperature and to provide distribution within a building.
Air-Dried LumberWood dried by exposing it to air.
Air-Entrained CementA Portland cement with an admixture that causes a controlled quantity of stable, microscopic air bubbles to form in the concrete.
Air-Entrained ConcreteConcrete with an admixture added that produces millions of microscopic air bubbles in the concrete.
Air-Supported StructureA membrane enclosing a pressurized occupied space, which must be held down to its foundation.
Airborne SoundSound traveling through the medium of air.
AlkydSynthetic resin modified with oil for good adhesion, gloss, color retention, and flexibility.
Allowable StressThe maximum unit stress permissible in a structural member. Also referred to as working stress.
AlloyA metallic material composed of two or more chemical elements one of which is a metal.
Aloying ElementAmu substance added to a molten metal to change its mechanical or physical properties.
Alternating CurrentAn electric current that varies periodically in value and direction by flowing first in one direction and then in the opposite direction.
AltitudeThe angle that the sun makes with the horizon.
AluminaA hydrated form of aluminum oxide from which aluminum is made.
Ambient TemperatureThe temperature of the surrounding air.
AmpereA basic SI unit that measures the rate of flow of electric current.
Anaerobic Bonding AgentsBonding agents that set hard when not exposed to oxygen.
AnchorMetal securing device embedded or driven into masonry, concrete, steel or wood.
Anchor BoltHeavy, threaded bolt embedded in the foundation to secure sill to foundation wall or bottom plate of exterior wall to concrete floor slab.
Angle of ReposeThe angle of the sloped surface of the sides of an excavation.
AnnealingHeating a metal to a high temperature followed by controlled cooling to relieve internal stresses.
Annular Ring NailA deformed shank nail with improved holding qualities specially designed for use with gypsum board.
AnodizingAm electrolytic process that forms a permanent, protective oxide coating on aluminum.
ANSIAmerican National Standards Institute, a nonprofit, national technical association that publishes standards covering definitions, test methods, recommended practices and specifications of materials. Formerly American Standards Assn. (ASA) and United States of America Standards Institute (USASI).
APA Performance-Rated PanelsPlywood manufactured to the structural specifications and standards of APA – The Engineered Wood Association.
AquiferAn underground permeable material through which water flows.
Arc ResistanceThe total elapsed time in seconds and electric current must arc to cause a part to fail.
ArchA curved structure in which the internal stresses are essentially compression.
Architectural Terra CottaClay masonry units made with a textured or sculptured face.
Area Separation WallResidential fire walls, usually with a 2- to 4-hour rating, designed to prevent spread of fire from an adjoining occupancy; extends from foundationGlossFoundation.1041 to or through the roof. Identified by codes as either “fire wall”, “party wall” or “townhouse separation wall.”
ASAFormerly American Standards Assn., now American National Standards Institute (ANSI).
AsphaltDark brown to black hydro-carbon solids or semisolids having bituminous constituents that gradually liquify when heated.
ASTMFormerly American Society for Testing and Materials, now ASTM, a nonprofit, national technical society that publishes definitions, standards, test methods, recommended installation practices and specifications for materials.
AttenuationReduction in sound level.
AutoclaveA high-pressure steam room that rapidly cures green concrete units.
Awning WindowA window that pivots near the top edge of the sash and projects toward the exterior.
Axial LoadA longitudinal load that acts at the centroid of a member and perpendicular to it’s cross section.
Axminster ConstructionCarpet formed by weaving on a loom that inserts each tuft of pile individually into the backing.
AzimuthA horizontal angle measured clockwise from North or South.