ABS    A type of black plastic (acroylonitrile-butadiene-styrene) pipe commonly used for waste water lines.
Aggregate    A mixture of cement, sand and rock that becomes concrete when mixed with water. Crushed rock used as a top layer in some flat-roof applications.
Airway    A space between roof insulation and roof boards for movement of air.
Algae    Microorganisms that may grow to colonies in damp environments, including certain rooftops. Often described as fungus. Algae can discolor shingles.
Amperage or AMPS    A unit of electrical current. Single-family residences have an electrical service of 100 amps or more. Circuits within the residence vary from 15 to 40 amps depending on what electrical needs they service. Some older homes have 60 to 100-amp service.

Anchor bolts    'L' shaped bolts that are set in the concrete foundation and used to attach the framing of the house, via the sill plate, to the concrete foundation.
Angle iron    A section of a strip of structural steel bent to form a right angle.
APA Plywood    APA=American Plywood Association, number one rated exterior plywood, contains no voids between laminate layers.
Apron    The flat member of the inside trim of a window placed against the wall immediately beneath the stool.
Apse    A projecting part of a building that is usually semicircular in plan and vaulted
Architect    One who has completed a course of study in building and design, served an internship, and is licensed as an architect. The architect is normally the prime design professional in the construction of buildings. The architect generally contracts with the owner or with a "turnkey" contractor. The architect usually obtains the services of civil, structural, electrical engineers as well as landscape architects. The architect produces a set of plans and specifications on which the construction contract is based.

Architrave    Lowermost part of an entablature
Area drain    A drain set in a flat area that cannot be drained otherwise. This might be the floor of a basement, entryway, exterior concrete flat work, or landscaping
Area separation wall    A fire-rated wall (e.g. one-hour) that extends from ground to roof for the purpose of restricting the spread of fire from one area of a large building to another.
Areaway    An open subsurface space adjacent to a building used to admit light or air or as a means of access to a basement.
Asbestos    1. A common form of magnesium silicate which was used in various construction products due to its stability and resistance to fire. The inhaling of asbestos fibers is associated with various forms of lung disease. 2. The name given to certain inorganic minerals when they occur in fibrous form. Though fire-resistant, its extremely fine fibers are easily inhaled, and exposure to them over a period of years has been linked to cancers of the lung or lung-cavity lining and to asbestosis, a severe lung impairment.
Asphalt    A bituminous material employed in roofing materials because of its waterproofing ability. Most native asphalt is a residue from evaporated petroleum. It is insoluble in water but soluble in gasoline and melts when heated.
Asphalt plastic cement    An asphalt-based cement used to bond roofing materials. Also known as flashing cement or mastic.
Attic ventilator    Screened openings provided for ventilating an attic space.