ABS: A type of black plastic pipe commonly used for waste water lines.

Aggregate: Crushed rock used as a top layer in some flat-roof applications.

Algae: Micro organisms that may grow to colonies in damp environments, including certain rooftops. Often described as fungus, algae can discolor shingles.

Allowances: A sum of money set aside in the construction contract for items which have not been selected and specified in the construction contract. Best kept to a minimum number and used for items who’s choice will not impact earlier stages of the construction. For example, selection of tile as flooring may require an alternative framing or underlayment material.

Amperage or AMPS: A unit of electrical current or volume- see voltage. Most homes have an electrical service ‘entrance’ package of 125 or 200 amps. Some older homes have 60 or 100 amp ‘entrances’.

Anchor Bolts: ‘L’ shaped bolts which are set in the concrete foundation and used to attach the framing of the house to the foundation.

APA Plywood: APA=American Plywood Association, number one rated exterior plywood, contains no voids between laminate layers.

Asbestos: (1) A common form of magnesium silicate which was used in various construction products due to it’s stability and resistance to fire. Asbestos exposure by inhaling loose 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.

Asphalt plastic cement: An asphalt-based cement used to bond roofing materials. Also known as flashing cement or mastic.