Building Glossary A



A Joining - See Joining.


AA - Acronym for Aluminum Association.


AAA - Acronym for American Arbitration Association.


AAC - Initials representing Autoclaved Aerated Concrete.


AAMA - Acronym for Architectural Aluminum Manufacturere's Association or American Architectural/Manufacturers Association.


Abacus - The top component of a column capital.


Abamurus - A masonry buttress for the support of a wall.


Above Grade - The portion of a building that is above ground level.


Abrams Law - The rule stating that with given materials, curing, and testing conditions, concrete strength is inversely related to the ratio of water co cement.  Low water-to-cement ratios produce high strengths.


Abrasion - the process of wearing away a surface by friction.


Abrasion Resistance - Ability of a coating/surface to resist degradation caused by mechanical wear (mechanical erosion) due to its ability to dissipate the applied mechanical energy.  Abrasion resistance can be enhanced by incorporation of surface modifying additives.  Abrasion resistance is not necessarily related to hardness as believed by some, but is more clearly comparable with toughness.


Abrasive(s) - (1) A hard material used for wearing away or polishing a surface by friction.  (2) The material that is adhered to or embedded in a surface such as sandpaper or a whetstone.  (3) Substances rubbed on wood to smooth the surface.  Flint, gamet, aluminum oxide, and silicon carbide are common abrasives.


Abrasive Aggregate - the aggregate used to increase the abrasiveness of the surface of a concrete slab.


Abrasive Blasting - A method of cleaning surfaces with a high-pressure stream of air and an abrasive material such as sand or steel grit.


Abrasive Floor - A floor with an abrasive adhered to or embedded in the surface to provide traction and prevent sloping.


Abrasive Nosing - A strip or anti-skid abrasive adhered to or attached to the nosing of a stair tread.


Abrasive Stair Tread - A stair tread with an abrasive surface.


ABS - Acronym for Acrylonitrile-Butadiene-Styrene, a type of plastic pipe used primarily for drain lines and vents. Generally a black colored plastic pipe and fittings used in drainage, waster, sewer and vent systems of both residential and commercial applications.  ABS and PVC plastics have replaced much of the cast iron, lead and steel pipes formerly used for DWV (Drain, Waste, and Vent) systems.  It is important to note that no solvent cement (and primer) can totally adhere ABS to PVC plastic.  Also under normal conditions, quality ABS (where virgin resins are used) will not crack, chip or peel.   Most common grade for ABS piping is schedule 40.(Modified 3/9/2008)


Absolute Humidity - (1) Absolute humidity defines the mass of water vapor in a given volume of most air or gas, and is usually reported in grams per cubic meter, although grains per cubic foot is more commonly used in the United States.  The ability of air to hold water vapor depends on the air temperature.  As temperature increases, air's capacity to hold water vapor increases.  As temperature decreases, air's capacity to hold water vapor decreases. (2) The ratio of the mass of water vapor present to the volume occupied by the mixture.  It represents the density of water vapor in the air.


Absolute Pressure - Is the sum of gauge and atmospheric pressure (psia).  See Pressure.


Absolute Temperature - Is temperature measured on the Kelvin scale.


Absolute Zero - The lowest temperature theoretically attainable on the Kelvin scale.  Approximately -273.16 degree-Celcius


Absorbent - (1) A material that has an affinity for certain substances and attracts these substances from a liquid or gas with which it is contact, thus changing the physical and/or chemical properties of the material.  (2) A substance that attracts and holds large quantities of liquid.  (3) A substance with the ability to absorb another substance.


Absorber Plate - That part of a solar energy system that collects the solar energy.


Absorption/Absorb - (1) The process by which a liquid is drawn into the pores of a permeable material.  (2) The process by which solar energy is collected on a surface.  (3) The increase in weight of a porous object resulting from immersion in water for a given time, expressed as a percent of the dry weight. (4) In physics, the taking up of light, heat, or other energy by molecules.  The absorbed energy is converted into heat.  Absorption in chemistry is the taking up on one substance by another.  For example, a gas such as oxygen may be absorbed, or dissolved, in water.  In the HVAC industry heat energy is absorbed from the medium being cooled and transfers that energy in the refrigerant.  (5) Refers to the process of one material attracting and retaining foreign particles such as gas or liquid without transmission of these particles.


Absorption Chiller - A water chilling process in which cooling is accomplished by the evaporation of a fluid (usually water), which is then absorbed by a different solution (usually lithium bromide), than evaporated under heat and pressure.  The fluid is then condensed with the heat of condensation rejected through a cooling tower.  (Definition:  Washington State University Cooperative Extension Energy Program)


Absorption Loss - (1) Water losses that occur until soil particles are sufficiently saturated, such as in filling a reservoir for the first time.  (2) Water losses that occur until the aggregate in a concrete mix is saturated.


Absorption Rate - The weight of water absorbed by a brick or concrete masonry unit that is partially immersed in water for one minute, expressed in grams or ounces per minute.  Often referred to as the "Initial Rate of Absorption".


Abstract of Title - A condensed version of the history of title to a piece of land that lists any transfers in ownership, as well as any liabilities attached to it, such as mortgages.


Abut - To join or touch at one edge or end without overlapping.


Abutment - (1) The structure that supports the end of a bridge or that anchors the cables of a suspension bridge.  (2) The surface at which one member abuts another.


Abutting - The joining, reaching, or touching of adjoining land.  Abutting pieces of land have a common boundary.


AC - Abbreviation or acronym for:  (1) Air-Conditioning,  (2) Alternating Current (on drawings),  or (3) Asbestos Cement


AC (Alternating Current) - A flow of electrons which regularly reverses its direction of flow.  60 cycles per second is the U.S. and Canadian Standard.  One cycle per second is called one Hertz (Hz).  AC can not be stored like DC in a battery. 


AC Generator - A generator that produces alternating current.  Because of how generators work the switching of peak positive current to peak negative current takes place gradually in a sine wave pattern. 


A/C - An abbreviation for air conditioner or air conditioning.


A/C Circuit - (Alternating Current) The flow of current through a conductor first in one direction then in reverse.  It is used exclusively in residential and commercial wiring because it provides greater flexibility in voltage selection and simplicity of equipment design.


A/C Condenser - the outside fan unit of the Air Conditioning System.  It removs the heat from the freon gas and coverts the gas back into a liquid stage and pumps it back to the coil (normally A-coil) located in the furnace.


A/C Disconnect - The main electrical ON-OFF switch near the A/C Condenser.  NOTE: For disconnect location IRC 4001.5 & NEC 440.14 applies.  Working clearance is covered by IRC 3305.1 & NEC 110.26A.


Accelerated Weathering - A test designed to simulate but at the same time intensify and accelerate the destructive action of natural outdoor weathering.


Acceleration - (1) An increase in velocity or rate of change.  (2) The ordered or voluntarily expedited performance of construction work at a faster rate than anticipated in the original schedule, the purpose of which is to recapture project delay.  This is accomplished by increasing labor hours and other resorces.  (3) The speeding up of the setting or hardening process of concrete by using an additive in the mix.  the process of acceleration allows forms to be stripped sooner or floors finished earlier.


Acceleration Clause - A provision in a written mortgage, note, bond or conditional sales contract that, in the event of default, the whole amount of principal and interest may be declared to be due and payable at once.


Accelerator - (1) A substance/additive which, when added to concrete, mortar, or grout, increases the rate of hydration of the hydraulic cement, shortens the time of setting, or increases the rate of hardening of strength development, or both.  In addition an accelerator may be added to paint products to speed the hardening process.  (2) A substance used in small proportions to increase the speed of a chemical reaction.  Accelerators are used to hasten the curring of a coating system.  Also known as catalyst.


Accent Lighting - Fixtures or directional beams of light arranged so as to bring attention to an object or area.


Acceptance - An offeree's consent to enter into a contract and be bound by the terms of the offer.


Access - (1) The means of entry into a building, area, or room.  (2) A port or opening through which equipment amy be inspected or repaired.


Access Control System - Computerized building security equipment, such as card readers, designed to protect against unauthorized entry into buildings or building zones.


Access Door/Panel - (1) A means of access for the inspection, repair, or service of concealed systems, such as air-conditioning equipment or a electrical service panel.  (2) A cover for a portal necessary to reach plumbing or electrical systems behind a wall.


Access Eye - A fitting provided at drainpipe bends for rodding.


Access Flooring - A raised flooring system with removable panels to allow access to the area below.  This type of flooring is frequently used in computer rooms because it provides easy access to cables.


Access Floor System - Is an assembly consisting of panels mounted on pedestals to provide an under-floor space for the installations of mechanical, electrical, communication or similar systems or to serve as an air-supply or return-air plenum.


Accessible - (1) Signifies access that requires the removal of an access panel or similar removable obstruction.   Access without the necessity for removing a panel or similar obstruction is referred to as "Readily Accessible". (2) (As applied to wiring) Capable of being removed or exposed without damaging the building structure or finish, or not permanently closed in by the structure or finish of the building; (3) (as applied to equipment) Admitting close approach by not being inaccessible because of guarded or locked doors, elevation, or other effective means.  (4) (as applied to Americans with Disability Act) a site, building facility, or portion thereof that complies with ADA requirements.


Accessible Equipment - Admitting close approach, not guarded by locked doors, elevation, or other effective means.  (Reference:  2006 IRC, Chapter 34, Electrical Definitions, Section E3401, page 477).


Accessible Means of Egress - A continuous and unobstructed way of egress travel from any  point in a building or facility that provides an accessible route to an area or refuge, a horizontal exit, or a public way.


Accessible Route - A continuous unobstructed path connecting all accessible elements and spaces of a building or facility.  Interior accessible routes may include corridors, floors, ramps, elevators, lifts, and clear floor space at fixtures.  Exterior accessible routes may include parking access aisles, curb ramps, crosswalks at vehicular ways, walks, ramps, and lifts.


Accessible, Readily - Capable of being reached quickly for operation, renewal, or inspections, without requiring those to whom access is requisite to climb over or remove obstacles or to resort to portable ladders, and so forth.  (Reference:  2006 IRC, Chapter 2, DEFINITIONS, Section R202, page 9; and 2006 IRC, Chapter 34, Electrical Definitions, Section E3401, page 477)


Accessible Wiring - Capable of being removed or exposed without damaging the building structure or finish, or not permanently closed in by the structure or finish of the building.  (Reference:  2006 IRC, Chapter 34, Electrical Definitions, Section E3401, page 477).


Accessory Structure - A structure not greater than 3,000 square feet in floor area, and not over two stories in height, the use of which is customarily accessory to and incidental to that of the dwelling(s) and which is located on the same lot.


Accordian Door - A retractable door, usually fabric-faced, hung from an overhead track and volding like the bellows of an accordion.


Accordian Partition - A retractable partition having the same features as an accordion door.


Accouplement - (1) In architecture, the pairing of plasters or columns, as in a colonnade or buttress.  (2) In carpenty, a tie or brace between timbers.


Accreditation Body - Is an approved, third-party organization that initially accredits and subsequently monitors, on a continuing basis, the competency and performance of a grading or inspection agency related to carrying out specific tasks. 


Accretion - An addition to land through natural causes.


Accrued Depreciation - The total reduction of the value of property as stated on a balance sheet for accounting or tax purposes.


Accumulator - A shell device installed in the suction line of a HVAC system to prevent liquids from entering the compressor.


Acetone - A highly flammable organic solvent used with lacquers, paint thinners, paint removers, and resins.


Acetylene - A carbon gas which, when combined with pure oxygen and ignited, produces an extremely hot flame used in gas welding and metal cutting.


Acetylene Torch - The torch used for welding and cutting.  Contains compressed acetylene and oxygen.


ACH - Air changes per hour.  the amount of air in a building that leaks out or is removed by a fan and is replaced by outdoor air.  Usually listed as a fraction of one air change per hour, such as .35 ACH.


ACI - Acronym for the American Concrete Institute, P.O. Box 9094, Farmington Hills, Michigan  48333


Acid - A liquid that has a ph of less than 7.0.


Acid Etch - (1) A method of cleaning the latence from concrete by washing it with an acid solution and rinsing with water.  (2) The use of a strong acid to remove the surface of concrete thereby exposing the aggregate; the use of a strong acid to etch the surface of material such as metal in order that that material to accept a primer or Spray Polyurethane Foam.


Acid Proof Floor - A floor that resists deterioration when exposed to acid.


Acid Resistance - A measurement of a surface's ability to resist the corrosive effect of acids.


Acid Resistant Brick - Brick that resists deterioration caused by exposure to acid.  This type of brick should be laid with acid-resistant mortar.


Acid Soil - Soil with a ph value of less than 6.6.


Acid/Alkali Resistant Grout or Mortar - A grout or mortar that is highly resistant to prolonged exposure to acid liquids, alkaline compounds or gases.


ACIL - Acronym for American Council of Independent Laboratories.


Acknowledgment - A declaration made by a person to a notary public, or other public official authorized to take acknowledgments, that the instrument was executed by him and that it was his free and voluntary act.


A-Coil - The part of the air conditioner system that is located inside the air handler.  Its primary function is to absorb the heat from the air.


Acoustic(s) - Science dealing with the production, control, transmission, reception and effects of sound, and the process of hearing. 


Acoustic Block - A masonry block with sound-absorbing qualities.  Also known as Acoustical Block.


Acoustic Lining - Insulating material secured to the inside of ducts to attenuate sound and provide thermal insulation.  Also known as Acoustical Lining.


Acoustical - A term used to define systems incorporating sound control.


Acoustical Barrier - A building system that restricts sound transmission.


Acoustical Board - A construction material in board form that restricts or controls the transmission of sound.


Acoustical Ceiling - A ceiling system constructed of sound control materials.  The system may include lighting fixtures and air diffusers.


Acoustical Door - A door constructed of sound-absorbing materials and installed with gaskets around the edges.


Acoustical Enclosure/Booth/Room - An enclosure constructed of acoustical materials for privacy in speaking, listening, and recording, as in a recording studio or a telephone booth.


Acoustical Glass - A pane of glass composed of two lites with dead air space between them for sound absorption.  This type of glass is frequently used for interior applications.


Acoustical Material - A material fabricated for the sole purpose of absorbing sound.


Acoustical Metal Deck - A metal decking that includes a sound absorbing material installed at a small additional cost per square foot.


Acoustical Panel - Modular units composed of a variety of sound absorbing materials for ceiling or wall mounting.


Acoustical Partition - A term applied particularly to movable, demountable, and operable partitions with sound absorbing characteristics.


Acoustical Plaster - Wall and ceiling plaster that has sound absorbing characteristics.


Acoustical Reduction Factor - A value, expressed in decibels, that defines the reduction in sound intensity that occurs when sound passes through a material.


Acoustical Sealant - A caulking or joint sealant with acoustical characteristics.


Acoustical Tile - A term applied to modular ceiling panels in board form with sound-absorbing properties.  This type of tile is sometimes adapted for use on walls.


Acoustical Transmission Factor - The reciprocal of the sound reduction factor.  A measure of sound intensity as it passes through a material, expressed in decibles.


Acoustical Wallboard - Wallboard with sound-absorbing properties.


Acoustical Window Wall - Double-glazed window walls with acoustical framing.  This type of wall system is used particularly at airports.


Acoustics - (1) The science of sound transmission, absorption, generation, and reflection.  (2) In construction, the effects of these properties on the acoustical characteristics of an enclosure.


Acre - A common unit of land area measurement equal to 160 square rods, or 43,560 square feet.


Acrolein - An agent added to methyl chloride, to aid in the indication of refrigerant leaks when testing.


Acrylic - A general class of resinous polymers derived from esters, amides or other acrylic acid derivatives.  Commonly used as the finished thermoplastic skin as the finished surfaces of bathtubs and whirlpools.  Comes in sheets and is formed to the shape of the mold (tubs/showers) at the factory.  Fiberglass is normally added to the backside of the Acrylic to add strength.  (Modified 3/9/2008)


Acrylic Coating - A coating system with an acrylic resin base.


Acrylic Fibre - Fibre produced from polymerized acrylontrile, a liquid derivative of natural gas.  A tough economical fibre commonly used in commercial and residential carpets and draperies.


Acrylic Latex - Water-reducible paint made containing acrylic as some portion of the composition.  Other modifiers of the binder that may be addes to reduce cost or add specific properties include styrene, epoxy, and polyvinyl acetate (PVA).


Acrylic Plastic Glaze - A clear plastioc sheet that is bonded to glass and that increases the ability of the glass to resist breaking and shattering.


Acrylic/Acrylate Resin - In construction, clear, tough, thermoplastic resin manufactured in sheet and corrugated form, used as an adhesive, and as the main ingredient in some caulking and sealing compounds.


Acrylontrile Butadiene Styrene - See ABS.


Action Level for Radon - EPA recommends home owners take action to lower radon levels indoors when concentrations are above 4pCi/L.


Activated Alumina - A type of aluminum oxide that absorbs moisture (used in refrigerant driers).


Activated Carbon - A processed Carbon used in filter driers, commonly used in air filters to clean/purify the air.


Activator - The curing agent of a two component/compound coating system.


Active - Will corrode in the presence of moisture.


Active Cooling - Compressor driven air-conditioning.


Active Leaf - In a double leaf door, the leaf to which the latching or locking mechanism is attached.


Active Solar - Active solar uses mechanical devices such as photovoltaic panels to transfer collected heat from the sun to storage mediums and/or end use.  Thus, solar radiation is used by special equipment to provide our homes with space heating, hot water, and/or electricity.


Active Solar Energy System - A system that primarily collects and transfers solar energy using mechanical means that are not powered by solar energy.


Act Of God - An unforeseeable, inevitable event caused by natural forces over which an insurance policyholder has little or no control.  Examples are windstorms, floods, earthquakes, and lightning strikes.


Activated Carbon/Charcoal - A material obtained principally as a by-product of the paper industry and used in filters for absorbing smoke, odors, and vapors.


Active Leaf - In a double leaf floor, the leaf to which the latching or locking mechanism is attached.


Active Solar Energy System - A system that primarily collects and transfers solar energy using mechanical means that are not powered by solar energy.


Actual Age - The actual age of a building as opposed to effective age.  It is the objective age in years measured simply by the passage of time since it was constructed.  Effective age is a subjective measurement of the condition of a building, influenced mostly by the maintenance and upkeep carried out on the building over the years.


Actual Dimension - The real dimensional measurement of a piece of timber, masonry unit, or other construction material.


Acute Angle - An angle less than 90o.


Ad Valorem - Designates an assessment of taxes against property.  Literally, according to value.


ADA - Acronym for Americans with Disability Act.  Issued by the Department of Justice these governmental guidelines are published in Title III regulations (28 CFR Part 36).  The ADA Standards for Accessible Design are in Appendix A of the Title III Regulations.  To download and view a pdf version go to  The pdf version of the ADA Standards contains full formatted text and graphics, as published in the Code of Federal Regulations, complete with links to figures, graphics and cross-referenced sections.  The file is 4.5 MB in size and may take some time to open when operating under a slow internet connection. (Added 3/9/2008)


Adaptability - Design strategy that allows for multiple future uses in a space as needs evolve and change.  Adaptable design is considered a sustainable building strategy as it reduces the need to resort to major renovation or tearing down a structure to meet future needs.


Adaptive Reuse - Renovation of a building or site to include elements that allow a particular use or uses to occupy a space that originally was intended for a different use.


Adaptor/Adapter - (1) A widely diversified term used to describe various plumbing parts (i.e. male/female adaptor, pitless adaptor, etc.), electrical parts (i.e. plug adaptor, 230 Volt to 115 Volt Electrical Adaptor, etc.).  (2) Any device designed to match the size or characteristics of one item to those of another, particularly in the plumbing, air-conditioning, and electrical trades.


Addendum - A document describing an addition, change, correction, or modification to contract documents.  An addendum is issued by the design professional during the bidding period or prior to the award of contract, and is the primary method of informing bidders of modification to the work during the bidding process.  Addenda become part of the contract documents.


Addition - (1) An expansion to an existing structure, generally in the form of a room, floor, or wing.  An increase in the floor area or volume of a structure.  (2) A chemical added to cement at the time of its manufacture to help the process or to alter the cements characteristics.


Additional Principal Payment - A payment by a borrower of more than the scheduled principal amount due in order to reduce the remaining balance on the loan.


Additive - A substance that is added to a material to enhance or modify its characteristics, such as curing time, plasticity, color, or volatility.


Address System - An electronic audio system with a microphone and speakers installed for either fixed (permanent) or mobile use.  Wiring for a permanent system should be done prior to any finish work.


Adhesion - (1) The state in which two surfaces are held together by interfacial forces which may consist of valence forces or interlocking action, or both.  (2) The binding together of two surfaces by an adhesive.


Adhesion, mechanical - Adhesion between surfaces in which the adhesive holds the parts together by interlocking action.


Adhesion, specific - Adhesion between surfaces which are held together by valence forces of the same type as those which give rise to cohesion.


Adhesive - Generally, any substance that binds two surfaces together.  A natural or synthetic material, generally in paste or liquid form, used to fasten or glue boards together, lay floor tile or fabricate plastic laminates for counter tops, etc.


Adhesive Failure - Loss of bond of a coating or sealant from the surface to which it is applied.


Adiabatic - A change in gas condition where no heat is added or removed except in the form of work.


Adjustable Clamp - A temporary clamping device that can be adjusted for position or size.


Adjustable Door Frame - A door frame with a jamb that can be adjusted to accommodate different wall thickness.


Adjustable Rate Mortgage (ARM) - A mortgage loan whose interest rate fluctuates according to the movements of an assigned index or a designated market indicator - such as the weekly average of one-year U.S. Treasury Bills - over the life of the loan.,  To avoid constant and drastic fluctuations.  ARM's typically limit how often and by how much the interest rate can vary.


Adjustable Square - A carpenter's tool used for marking and scribing timber.  An adjustable square usually incorporates a level bubble.  Also known as a Double Square.


Adjustable Wrench - A wrench with a jaw that can be adjusted to fit different size nuts or bolt heads.


Adjusted Basis - The original cost of a property plus the value of any capital expenditures for improvements to the property minus any depreciation taken.


Adjuster - A representative of the insurance company who negotiates with all parties involved in a loss in order to settle the claim equitably.  An adjuster deals with the policyholder, repair contractor(s), witnesses, and police (if necessary), and acts as a middleman between these parties and the insurance company.


Adjustment - The determination of: (a) the cause of a loss; (b) whether it is covered by the policy; (c) the dollar value of the loss, and (d) the amount of money to which the claimant is entitled after all allowances and deductions have been made.


Adjustment Date - The date on which the interest rate changes for an Adjustable Rate Mortgage (ARM).


Adjustment Factor - A constant (usually a multiplier) used in any calculation.


Adjustment Period - The period that elapses between the adjustment dates for an Adjustable Rate Mortgage (ARM).


Adjustments - Money that the buyer and sellers credit each other at the time of closing.  Often includes taxes and loan payment.


Administrator/Administratrix - A man/woman appointed by a court to settle the estate of a deceased person when there is no will.  Contrast with executor/executrix.


Administrative Authority - A governmental agency that adopts or enforces regulation and guidelines for the design, construction, or alteration of buildings and facilities.


Admixture - An ingredient other than water, aggregates or hydraulic cement, that is added to a concrete or mortar mix to affect the physical or chemical characteristics of the concrete or mortar.  The most common admixtures affect plasticity, air entrainment, and curring time.


Adobe - An aluminous clay used to make unfired brick.


Adobe Brick - A large, roughly formed, unfired brick made from adobe and straw.


Adsorption - Adsorption, which is often confused with absorption, refers to the adhering of molecules of gases and liquids to the surfaces of porous solids.  Adsorption is a surface phenomenon; absorption is an intermingling or inter-penetration of two substances.


Adverse Possession - The right of an occupant of land to acquire title against the real owner, where possession has been actual, continuous, hostile, visible, and distinct for the statutory period.  The requirements for adversely possessing property vary between states, but usually include continuous and open use for a period of five or more years and paying taxes on the 's in question.


Adz - A long-handled tool with a curved blade set perpendicular to the handle.  Used for dressing lumber.


Aeolian - Wind-blown or transported by the wind.


Aerate - To introduce air into soil or water, for example, by natural or mechanical means.


Aerated Concrete - Concrete that has had gas-forming chemicals mixed with the basic ingredients, so that the final set material is lighter than ordinary concrete, due to its porosity.


Aeration - The process of introducing air into a substance or area by natural or mechanical means.


Aerator - (1) The round screened screw on the tip of a sink spout.  It mixes water and air for a smooth water flow.  (2) A mechanical device that introduces air into a material such as soil, water, or sewage.


Aerial - Pertaining to, caused by, or present in the air.


Aerial Platform - A term commonly applied to mobile working platforms that are elevated hydraulically or mechanically.


Aerosol - A product that is dispensed by a propellant from a metal can up to a maximum size of 33.8 fluid ounces (100mL) or a glass or plastic bottle up to a size of 4 fluid ounces (118.3mL), other than a rim-vented container.


Aerosol Paints - Paints packaged in a pressurized can with a spray nozzle attached.


Aesthetic Value - A subjective element in the overall market value of a property created by the physical presentation of the land or buildings.


Affidavit - Written statement signed and sworn to before some person authorized to take an oath.


A-frame - (1) A structural system or hoisting system with three members erected in the shape of an upright capital letter "A".  (2) A building with a steep gable roof that extends to the ground. Photos and History


AFUE - Abbreviation/Acronym for Annual Fuel Utilization Efficiency which measures the amount of fuel converted to space heat in proportion to the amount of fuel entering the furnace.  This is commonly expressed as a percentage.  A furnace with an AFUE of 90 could be said to be 90% efficient.  AFUE includes any input energy required by the pilot light but does not include any electrical energy for fans or pumps.  The U.S. Government's minimum efficiency level is 78%.  The higher the AFUE, the more efficient the furnace. 


AGA - Acronym for American Gas Association.  The AGA was founded in 1918, and represents a large contingency of companies that deliver natural gas to millions of homes, businesses and industries throughout the United States.  AGA is an advocate for natural gas utility companies and their customers and provides several programs and services.  Many appliances and gas valves carry the AGA approval rating. 


Agency - the legal relationship between a principal and an agent.  In real estate transactions, usually the seller is the principal, and the broker is the agent; however, a buyer represented by a broker (i.e. buyer as principal is a growing trend).  In an agency relationship, the principal delegates to the agent the right to act on his or her behalf in business transactions and to exercise some discretion while so acting.  The agent has a fidiuciary relationship with the principal and owes to that principal the duties of accounting, care, loyalty, and obedience.  Also see Buyer's Broker.


Agent - A person authorized to act for and under the direction of another person when dealing with third parties.  The person who appoints an agent is called the principal.  An agent can enter into binding agreements on the principal's behalf and may even create liability for the principal if the agent causes harm while carrying out his or her duties.  See also Attorney-In-Fact. 


Aggregate - Granular material such as sand, gravel, crushed gravel, crushed stone, slag, and cinders.  Aggregate is used in construction for the manufacturing of concrete, mortar, grout, asphaltic concrete, and roofing shingles.  It is also used in leaching fields, drainage systems, roof ballast, landscaping, and as a base course for pavement and grade slabs.  Aggregate is classified by size and gradation.  Cement and Concrete Basics 


Aggregate Panel - A precast concrete panel with exposed aggregate.


Aggregate Spreader - A piece of equipment used for placing aggregate to a desired depth on a roadway or parking lot.


Agricultural Building - A structure designed and constructed to house farm implements, hay, grain, poultry, livestock or other horticultural products.  This structure shall not be a place of human habitation or a place of employment where agricultural products are processed, treated or packaged, nor whall it be a place used by the public.


Agricultural Waste - Materials left over from agricultural processes (i.e., wheat stalks, shell hulls, etc.).  Some of these materials are finding new applications as building materials and finishes.  Examples include structural sheathing and particle board alternatives made from wheat, ruy and other grain stalks, and panels made from sunflower seed hulls.


AHJ - See Authority Having Jurisdiction.


AIA - Acronym for American Insurance Association, successor to the National Board of Fire Underwriters and a nonprofit organization of insurance companies.  Also the Acronym for the American Institute of Architects.


Air Admittance Valve - A mechanical one-way valve designed to allow air into the plumbing drainage system when a negative pressure develops in the piping.  This device shall close by gravity and seal the terminal under conditions of zero differential pressure (no flow conditions) and under positive internal pressure.


Air Balance - To distribute air through a system to precisely match the required amount.


Air Barrier - The primary function of an air barrier is to control airflow between a conditioned space and an unconditioned space.  Air barrier systems are a component of building envelope systems that control the movement of air in and out of buildings.  Many performance problems of homes can be traced to air leakage through the building envelope.  These problems include everything from high heating/cooling costs to poor temperature control in occupied spaces to moisture. 


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


Airborne Particulates - Total suspended particulate matter found in the atmosphere as solid particles or liquid droplets.  Chemical composition of particulates varies widely, depending on location and time of year.  Sources of airborne particulates include dust, emissions from industrial processes, combustion products from the burning of wlld and coal, combustion products associated with motor vehicle or non-road engine exhausts, and reactions to gases in the atmosphere.


Airborne Sound - Sound traveling through the medium of air.  Airborne Sound Transmission Loss Characteristics of Wood-Frame Construction


Air Break (Drainage System) - An arrangement in which a discharge pipe from a fixture, appliance or device drains indirectly into a receptor below the flood-level rim of the receptor, and above the trap seal. 


Air Brick - Perforated brick or grating set into wall to provide ventilation.  Most frequently used at the base of walls to ventilate areas beneath joist and boarded ground floors.


Air Changes Per Hour (ACH) - The movement of a volume of air in a given period of time;  if a house has one air change per hour, it means that the air in the house will be replaced in a one-hour period.  See ACH.


Air Change Effectiveness - A measurement of the performance of a ventilation system, by measuring the age of air in a volume.  Often accomplished by using a tracer gas decay technique.


Air Cleaning - Indoor-Air quality-control strategy to remove various airborne particulates and/or gases from the air.  Most common methods are particulate filtration, electrostatic precipitation, and gas sorption.


Air Conditioner - A device used to control temperature and humidity of the air.


Air Conditioning - To condition air, transfer of heat and humidity from one medium to another.


Air-Conditioning System - A system that consists of heat exchangers, blowers, filters, supply, exhaust and return-air systems, and shall include any apparatus installed in connection therewith. 


Air Dried Lumber - Lumber that has been piled in yards or shed for drying time.  The minimum moisture content of thoroughly air-dried lumber is usually 12 to 15%.  Air-dried lumber often has a higher moisture content than other types of lumber.  As opposed to kiln-dried lumber which has a lower moisture content and thus tends not to warp as much after installation.


Air Duct - Ducts, usually made of sheet metal, that carry temperature controlled air to all rooms.


Air Exchange Rate - the rate at which outside air replaces indoor air in a given space.  Expressed in one of two ways:  the number of changes of inside air per unit of time (Air changes per hour, ACH); or the rate at which a volume of outside air enters per unit of time (Cubic feet per minute, cfm).


Air Filters - Air filter elements capture particles and prevent them from entering the conditioned air stream.  Filters are available in a wide range of sizes and configurations depending on the application.  Examples of filter media include paper, sponge foam, spun glass and pleated woven bags.  Other filters include electrostatic particle arresting types where the filter media is electrically charged to make it more effective in attracting and capturing particles.  Activated charcoal filters are used to address unpleasant odors associated with vapors or gases, but they should always be used in conjunction with a particle filter.  Filters are placed ahead of key system components mainly to extend life, reduce maintenance and repair costs and prevent damage from dirt and other pollutants.  A secondary usage for filters is to prevent contaminants from dispersing throughout the ventilation system and into occupied areas, which could pose health hazards or create a dirty, dusty environment.


Air Flow Retarder - Sealants used to keep outside air and inside air out of the building envelope.  Four common approaches to retarding air flow include careful sealing using the following building components:  drywall and framing, plastic sheets (should not be used in hot and humid climates) between drywall and framing, exterior sheathing, and building paper.  Air flow retarders define the pressure boundary in a house that separates indoor and outdoor air.


Air Gap, Drainage System - The unobstructed vertical distance through free atmosphere between the outlet of a waste pipe and the flood-level rim of the fixture or receptor into which it is discharging.


Air Gap, Water-Distribution System - The unobstructed vertical distance through free atmosphere between the lowest opening from a water supply discharge to the flood-level rim of a plumbing fixture.


Air Handler/Air Handling Unit - Equipment that includes a fan or blower, heating and/or cooling coils, regulator controls, condensate drain pans, and air filters.  Does not include ductwork, registers or grilles, or boilers and chillers.


Air Infiltration - The amount of air leaking in and out of a building through cracks in walls, windows and doors.


Air-Impermeable - A material or assembly having an air permeance equal or less than 0.02 l/(sm2) @ 75 Pa tested according to ASTM E 2178 or E283.


Airlock - A blockage in a pipe caused by a trapped air bubble.


Air Plenum - Any space used to convey air in a building, furnace, or structure.  The space above a suspended ceiling is often used as an air plenum.


Air Pollutant - Any substance in the air that could, in high enough concentration, harm man, other animals, vegetation, or material.  Pollutants may include almost any natural or artificial composition of airborne matter capable of being airborne.  They may be in the form of solid particles, liquid droplets, gases, or in combination thereof.  Generally, the fall into two main groups:  (1) those emitted directly from identifiable sources, and (2) those produced in the air by interaction between two or more primary pollutants, or by reaction with normal atmospheric constituents, with or without photo-activation.  Exclusive of pollen, fox, and dust, which are of natural origin, about 100 contaminants have been identified.  Air pollutants are often grouped in categories for ease in classification;  Some of the categories are: solids, sulfur compounds, volatile organic chemicals, particulate matter, nitrogen compounds, oxygen compounds, halogen compounds, radioactive compound, and odors.


Air Quality Construction Management Plan - A systematic plan for addressing construction practices that can impact air quality during construction and continuing on to occupation.


Air Space - The area of space between insulation facing and interior of exterior wall coverings.  Normally a 1-inch air gap.


Air, Standard - Air having a temperature of 68-degree F. (20-degree C.) a relative humidity of 36% at 14.7 psi.


Air to Air - In HVAC both the condensing and evaporating mediums are air.


Air Vent - A valve, either manual or automatic that is used to remove unwanted air from the highest point of a piping system.


Airway - The space between a ceiling's insulation and the roof boards that allows air movement through the roofing systems vents, allowing moisture and summer heat buildup to escape.


AISC - Acronym for The American Institute of Steel Construction, Inc., One East Wacker Drive, Suite 3100, Chicago, Illinois 60601-2001


Alcohol Brine - Water and alcohol solution which remains in a liquid state below 32-degrees F.


Alcove - A recess opening off a wall of a larger room.  Often used as a sitting area, coat room, or storage area.


Algae Discoloration - A type of roof discoloration caused by algae growth.  Commonly called "fungus growth".


Alienation Clause - A clause in a mortgage, which gives the lender the right to call the entire loan balance due if the property is sold; due-on-sale clause.


Alkali - A chemical substance which effectively neutralizes acid material so as to form neutral salts.  A base. The opposite of acid.  Examples are ammonia and caustic soda.


Allergen - Something (including biological material such as fungi, mold, spores, insect parts, skin flakes, and chemical compounds) which causes an allergic reaction.


Alley - Any public way for throughfare less than 16 feet (4877 mm) but not less than 10 feet (3048 mm) in width that has been dedicated or deeded to the public for public use.


Alligatoring - (1) A condition of paint or aged asphalt brought about by the loss of volatile oils and the oxidation caused by solar radiation.  "Alligatoring" produces a pattern of cracks that resemble an alligators hide and is ultimately the result of the limited tolerance of paint or asphalt to thermal expansion and contraction.  (2) Shrinkage cracking of the surfacing bitumen on a built-up roof, producing a pattern similar to an alligator's hide.  The cracks may or may not extend through the entire surfacing bitumen thickness.


Allowance(s) - A sum of money set aside in the construction contract for items, which have not been selected and specified in the construction contract.  For example, selection of tile as a flooring may require an allowance for an underlayment material, or an electrical allowance, which sets aside an amount of money to be spent on electrical fixtures.


Alter/Alteration - (1) Any change, addition or modification in construction or occupancy.  (2) A change to a building or facility that affects or could affect the usability of the building or facility or portion thereof.  Alterations include, but are not limited to, remodeling, renovation, rehabilitation, reconstruction, historic restoration, resurfacing of circulation paths or vehicular ways, changes or rearrangement of the structural parts or elements, and changes or rearrangement in the plan configuration of walls and full-height partitions.  Normal maintenance, reroofing, painting or wallpapering, or changes to mechanical and electrical systems are not alterations unless they affect the usability of the building or facility.


Alternating Current - Electrical current which reverses direction regularly (60 hertz, or cycles per second, in the U.S.)  As opposed to DC or direct current which does not reverse direction.


Alternative Energy - Energy from a source other than the conventional fossil-fuel sources of oil, natural gas and coal (i.e., wind, running water, the sun).  Also referred to as "alternative fuel."


Alternative Fuels - Substitutes for traditional liquid, oil-derived motor vehicle fuels like gasoline and diesel.  Includes mixtures of alcohol-based fuels with gasoline, methanol, ethanol, compressed natural gas, and others.


Aluminum Gutters - Aluminum gutters are often one piece gutters.  Aluminum one piece gutters are formed with a machine (normally on-site) and are carried directly to the roof.  These systems are not labor intensive and are less costly than other systems.  They are prepainted and last many years.  They are easily bent so objects such as ladders should not be leaned against them unless absolutely necessary.  Gutter systems should be checked prior to each rainy season to insure that they are properly fastened and are not stopped up with leaves or debris.


Aluminum Windows - Aluminum windows are one of the most common windows in use today.  Aluminum is especially durable requiring no special attention unless exposed to salt air.  In salt air areas a regular maintenance program of applying a light coating of an oily substance will help ward off the effects of salt air.  Aluminum windows will often be painted or anodized with a color.


Aluminum Wire - Conductors made of aluminum for carrying electricity.  Aluminum generally is limited to the larger wire sizes.  Due to its lower conductivity, aluminum wire smaller than #12 is not made.  Aluminum is lighter and less expensive than copper but not as good of a conductor.  In addition aluminum wire is more prone to breakage which results into electrical arcing and possible fires.


Ambient Temperature - (1) The temperature of the air, water, or surrounding earth not influenced by any man made temperature differential.  (2) The temperature surrounding an object.


Amenities - Non monetary benefits and satisfactions derived from property ownership, such as a pleasant view, pride in home ownership, etc.


American Method - Application of giant individual shingles with the long dimension parallel to the rake.  Shigles are applied with 3/4-inch space between adjacent shingles in a course.


Amendment - A modification to an existing contract, mutually agreed to by all parties.  Examples might include a change in the purchase price due to a low appraisal, or a change in the closing date.


Ammeter - (1) An electric meter used to measure electrical current, calibrated in amperes.  (2) An Instrument for measuring the current in amps, milliamps or micro amps.


Amortization - (1) A home mortgage payment plan by which a loan is reduced through monthly payments of principal and interest.  (2) The operation of paying off indebtedness, such as a mortgage, by installments.  The conventional amoritization periods are 15 or 30 years.  See Term.


Amortized Mortgage - A mortgage requiring periodic payments that include both interest and principal.  Also see Self Amortized Loan.


Ampacity - the current, in amperes, that a conductor can carry continuously under the conditions of use without exceeding its temperature rating.  Reference:  2006 IRC, Chapter 34, ELECTRICAL DEFINITIONS, Section E3401, page 477).


Ampere, or Amp (A) or (I) - Unit of measurement of electric flow, or current, like volume of water in a stream.  A count of how many electrons pass a given point in one second.  A closed circuit is necessary for current flow.  Named after Andre Ampere, a French mathematician and physicist who quantified electric flow around/about the year 1820.


Amplitude - The highest value reached by voltage, current or power during a complete cycle.


Amps (Amperes) - See Ampere, or Amp (A) or (I).


Amusement Building - A building or portion thereof, temporary or permanent, used for entertainment or educational purposes and that contains a system that transports passengers or provides a walkway through a course so arranged that the means of egress are not apparent due to theatrical distractions, are disguised or are not readily available due to the method of transportation through the building or structure.


Analogue - A system in which data is represented as a continuously varying voltage.


Anchor(s) - (1) Any fastener (usually metal) used to attach parts, such as joists, trusses, posts, etc., to masonry or masonry materials.  (2) Devices for supporting, hanging and securing pipes, fixtures and equipment.


Anchor Bolts - Bolts which fasten columns, girders or other members to concrete or masonry such as bolts used to anchor sills to masonry foundations.  Foundation sills or plates shall be bolted to the foundation with not less than 1/2-inch diameter steel bolts embedded at least 7-inches into the concrete or reinforced masonry or 15-inches into unreinforced grouted masonry.


Anemometer - An instrument that measures air speed.


Angle Iron - A piece of iron that forms a right angle and is used to span openings and support masonry at the openings.  In brick veneer, they are used to secure the veneer to the foundation.  Also known as a shelf angle.


Angle Stop - A shut-off valve that is usually installed immediately before the water supply line connection to common fixtures such as toilets and faucets.  These valves were commonly installed for emergency shut-off systems to facilitate the repair or replacement of fixture parts such as faucets, without the disruption of water supply to the entire plumbing system.  In older homes these angle stops have been found to be inoperative or frozen and have often been attributable to additional headaches for the property owner.  The difference between a "straight" and "angle" stop varies in that an "angle" stop changes flow direction by 90-degree while a "straight" stop is like most valves and does not change the flow direction.  (Added 3/9/2008)


Animal Dander - Tiny scales of animal skin.


Annealing - In the manufacturing of float glass, it is the process of controlled cooling done in a lehr to prevent residual stresses in the glass.  Re-annealing is the process of removing objectionable stress in glass by re-heating to a suitable temperature followed by controlled cooling.


Annual Fuel Utilization Efficiency - See AFUE.


Annual Membership - The amount that is charged annually for having a line of credit available.  Often charged regardless of whether or not you use the line.


Annual Percentage Rate (APR) - Annual cost of credit over the life of a loan, including interest, service charges, points, loan fees, mortgage insurance, and other items.


Anode Rod - Anode rods are designed to help protect the tank of a water heater by reducing internal corrosion.  Anode rods generally last about five years but it really depends mostly on the quality of the water and how much water travels through the water heater.  When sodium is added to the water (such as when a water softener is used) anode rods can corrode more quickly.  Water softeners can help reduce sediment, but anodes can corrode in as little as six months if the water is over-softened.  Failure to replace or maintain anode rods leads to the possibility of the anode rod becoming broken off, and then falling to the bottom of the water heater and bouncing around whenever water travels inside the water heater.  This in turn may cause cracks in the glass lining of the water heater or radically shorten the life of the water heater through deterioration or rust.  (Added 3/9/2008)


ANSI - Acronym for The American National Standards Institute, 1430 Broadway, New York, New York 10018


Anticipation - to realize in advance, i.e., a heat anticipator on a thermostat is used to shut down a furnace prior to the set point, as we are anticipating that the furnace will continue to run until the heat exchange is cooled and we will be at set point by that time.


Antisiphon - A term applied to valves or mechanical devices that eliminate siphonage.  Landscape Irrigation Antisiphon System Tutorial   


Antitrust Laws - Federal and State laws prohibiting, among other things, monopolies, monopolistic practices, restraint of trade, and price fixing. 


Anti-Walk Blocks - Elastomeric blocks that limit lateral glass movement in the glazing channel which may result from thermal, seismic, wind load effects, building movement, and other forces that may apply.


Apartment House/Building - Any building or portion thereof that contains three or more dwelling units.


Appliance - (1) Utilization equipment, generally other than industrial, that is normally built in standardized sizes or types and is installed or connected as a unit to perform one or more functions such as clothes washing, air conditioning, food mixing, deep frying, and so forth.  (2) Any machine or device that is powered by electricity.  (Reference:  2006 IRC, Chapter 34, ELECTRICAL DEFINITIONS, Section E3401, page 477).


Application - An initial statement of personal and financial information, which is required to approve a loan.


Application Fee - Fees that are paid upon application for a loan.  Charges for property appraisal and a credit report are usually included in the application fee.


Application Rate - The quantity (mass, volume or thickness) of material applied per unit area. 


Appraisal - A determination of the value of something, such as a house, jewelry or stock.  A professional appraiser - a qualified, disinterested expert - makes an estimate by examining the property, and looking at the initial purchase price and comparing it with recent sales of similar property.  Courts commonly order appraisals in probate, condemnation, bankruptcy or foreclosure proceedings in order to determine the fair market value of property.  Banks and real estate companies use appraisals to ascertain the worth of real estate for lending purposes.  Insurance companies require appraisals to determine the amount of damage done to covered property before settling insurance claims.


Appraised Value - An estimate of the present worth.


Appreciation - An increase in value or worth of property.  Opposite of depreciation.


Approach - The area between the sidewalk and the street that leads to a driveway or the transition from the street as you approach a driveway.


Approved -  (1) Meets acceptable requirements of some type of certifying authority, such as local building code officials, or written standards of such organizations such as ASTM or UL, ICC and many others.  (2)  Acceptable to the authority having jurisdiction.  (3) As to materials and types of construction, refers to approval by the building official as the result of investigation and tests conducted by the building official, or by reason of accepted principles or tests by recognized authorities, technical or scientific organizations. 


Approved Agency - An established and recognized agency regularly engaged in conducting tests or furnishing inspection services, when such agency has been approved by the building official.


Approved Fabricator - An established and qualified person, firm or corporation approved by the building official.


Apron - A trim board that is installed beneath a windowsill (stool) on the interior side of the window.


Arcade - A series of arches supported by columns or piers to provide an open passageway.


Arc-Fault Circuit Interrupter (AFCI) - A device with the purpose of providing protection from arc-faults by recognizing characteristics unique to arcing and by functioning to de-energize or shut-down the circuitry (by tripping) when an arc-fault is detected.  (Reference:  2006 IRC, Chapter 34, ELECTRICAL DEFINITIONS, Section E3401, page 477).


Arch - A curved structure that will support itself and the weight above its curved opening by mutual pressure.


Arched Roof - Arched roofs are usually found on larger commercial buildings.  They are almost always metal truss systems and most often have parapet walls around the outer edges.  The parapet walls vie the building a larger appearance with a square commercial look but also act as dams which hold water from running off the roof.  Water is usually directed to roof drains or scuppers, then into downspouts or pipes.  It is recommended by experts that the roof drains for inspected and cleared of debris at least twice per season.


Architect - One who has completed a course of study in building and design, and is licensed by the state as an architect.  The Architect is a tradesman who designs and produces plans for buildings, often overseeing the building process.


Architects Rule (Ruler) - Three sided ruler with different scales on each side.  Also referred to as a "scale".


Area Divider - 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 in a roof system where no expansion joints have been provided.


Areaway - Recessed area below grade around the foundation to allow light and ventilation into basement window.


Area Wells - Corrugated metal or concrete barrier walls installed around a basement window to hold back the earth.


Aromatic Red Cedar - Similar characteristics to (Western red cedar), primarily used in construction for chests and closet linings for its mothproof value.


Arrestance - The ability of a filter to remove injected standard dust from the test air.


Arris - A sharp edge formed when two planes or surfaces meet.  Found on edges of moldings, doors, shelves, and in cabinet construction.


Asbestos - (1) A group of natural, fibrous, impure silicate materials.  (2) A mineral fiber that can pollute air or water and cause cancer or asbestosis when inhaled.  The Environmental Protection Agency has banned or severely restricted its use in manufacturing and construction.


Ashpit - The area below the hearth of a fireplace, which collects the ashes.


ASHRAE - American Society of Heating, Refrigeration and Air Conditioning Engineers is an international group which is organized for the purpose of advancing the arts and sciences of heating, ventilation, air conditioning and refrigeration through research, standards writing, continuing education and publications.


Asking Price - The price placed on property for sale or the List Price.


Aspect Ratio - The ratio of the height to width (h/w) of a shear wall.  The shear wall height is the maximum clear height from top of foundation or diaphragm to bottom of diaphragm framing above and the shear wall width is the sheathed dimension in the direction of applied force on the shear wall.


Asphalt - A dark brown to black cementious material whose predominating constituents are bitumens that occur in nature or are obtained in pertoleum processing.


Asphalt Felt - An asphalt-saturated felt or an asphalt coated felt.


Asphalt Mastic - A mixture of asphaltic material and graded mineral aggregate that can be poured when heated but requires mechanical manipulation to apply when cool.


Asphalt Plastic Roofing Cement - An asphalt-based cement used to bond roofing materials.  Also known as "Flashing Cement", or "Mastic".  ASTM D-4586 is the Testing Standard that applies.


Asphalt Shingles - Composition roof shingles made from asphalt impregnated felt covered with mineral granules.


Asphaltene - A high molecular weight hydrocarbon fraction precipitated from asphalt by a designated paraffinic naphtha solvent as a specified temperature and solvent-asphalt ration.  NOTE:  The asphaltene fraction should be identified by the temperature and solvent asphalt ratio used.


Aspiration - The movement is a fluid produced by suction.


Assembly Area - A room or space accommodating a group of individuals for recreational, educational, political, social, civic, or amusement purposes, or for the consumption of food and drink.  Assembly type areas include, but are not limited to, classrooms, lecture halls, courtrooms, public meeting rooms, public hearing rooms, legislative chambers, motion picture houses, auditoriums, theaters, playhouses, dinner theaters, concert halls, centers for the performing arts, amphitheaters, arenas, stadiums, grandstands, or convention centers.


Assembly Building - A building or portion of a building used for the gathering together of 50 or more persons for such purposes as deliberation, education, instruction, worship, entertainment, amusement, drinking or dining, or awaiting transportation.


Assembly Group A Occupancy - Assembly Group A occupancy includes, among others, the use of a building or structure, or a portion thereof, for the gathering together of persons for purposes such as civic, social or religious functions, recreation, food or drink consumption or awaiting transportation.


Assessment - A tax levied on a property, or a value placed on the worth of a property.


Assessor - A local government official who determines the value of the property for taxation purposes.


Assignee - A person to whom a property right is transferred.  For example, an assignee may take over a lease from a tenant who wants to permanently move out before the lease expires.  The assignee takes control of the property and assumes all the legal rights and responsibilities of the tenant, including payment of rent.  However, the original tenant remains legally responsible if the assignee fails to pay the rent.


Assignment - A transfer of property rights from one person to another, called the assignee.


Assignor - A person who makes an assignment for a mortgage or contract for a home or piece of property.


Assistive Listening System (ALS) - An amplification system utilizing transmitters, receivers, and coupling devices to bypass the acoustical space between a sound source and a listener by means of induction loop, radio frequency, infrared, or direct-wired equipment.


Assumable Mortgage - An existing mortgage that can be taken over by the buyer on the same terms given to the original borrower.


Assumption - Allows a buyer to assume responsibility for an existing loan instead of getting a new loan.


Assumption of Mortgage - The transfer of title to property to a grantee wherein he assumes liability for payment of an existing note secured by a mortgage against the property; should the mortgage be foreclosed and the property sold for a lesser amount than that due, the grantee-purchaser who has assumed and agreed to pay the debt secured by the mortgage is personally liable for the deficiency.  Before a seller may be relieved of liability under the existing mortgage, the lender must accept the transfer of liability for payment of the note.  Also known as simple assumption.  Contrast with subject to mortgage.


ASTM - Acronym for The American Society for Testing and Materials, 100 Barr Harbor Drive, West Conshohocken, Pennsylvania 19428.  A voluntary organization concerned with development of consensus standards, testing procedures and specifications.


Astragal (Double Doors) - A molding, attached to one of a pair of swinging double doors, against which the other door strikes.


Astragal (Garage Doors) - Weather-stripping that runs along the bottom of the garage door, stopping any drafts or rain from entering the garage.


Atmospheric Condenser - A condenser operated with water that is exposed to the atmosphere.


Atmospheric Dust Spot Efficiency - The measurement of a devices ability to remove dust from the air.


Atmospheric Pressure - Is the pressure that the atmosphere exerts.  At sea level it is 14.7 psig also written as 29.92"Hg.


Atrium - An opening through two or more floor levels other than enclosed stairways, elevators, hoistways, escalators, plumbing, electrical, air-conditioning or other equipment, which is closed at the top and not defined as a mall.  Floor levels, as used in this definition, do not include balconies within assembly occupancies or mezzanines.


Attached Housing - Duplex, triplex, row housing, or townhouses.  Two or more dwellings that are attached physically but are owned and/or occupied by different people.


Attachment - Method by which a debtors' property is placed in the custody of the law and held as security pending outcome of a creditor's suit.


Attachment Plug - A device that, by insertion in a receptacle, establishes a connection between the conductors of the attached flexible cord and the conductors, connected permanently to the receptacle.  Also known as a "plug" or "plug cap".  (Reference:  2006 IRC, Chapter 34, ELECTRICAL DEFINITIONS, Section E3401, page 477)


Attic - The space between the ceiling joists of the top story and the roof rafters.


Attic Access - An opening that is placed in the dry walled ceiling of a home providing access to the attic.  May also be referred to as a "scuttle".   Energy Technical Bulletin


Attic Ventilators - In houses, screened openings provided to ventilate an attic space.  They are located in the soffit area inlet ventilators and in the gable end or along the ridge as outlet ventilators.  They can also consist of power-driven fans used as an exhaust system.  See Louver.


Attorney's Opinion of Title - An instrument written and signed by the attorney who examines the abstracts of title, stating his opinion as to whether a seller may convey good title.


Attractive Nuisance - Something on a piece of property that attracts children but also endangers their safety.  For example, unfenced swimming pools, open pits, farm equipment and abandoned refrigerators have all qualified as attractive nuisances.


Auction - A public sale of property to the highest bidder.


Auger - In carpentry, a wood-boring tool used to bore holes.


Authority Having Jurisdiction (AHJ) - The organization, office, or individual responsible for approving equipment, materials, installation, or a procedure.  Authority Having Jurisdiction or AHJ is used in a broad manner, since jurisdictions and approval agencies vary, as do their responsibilities.  Where public safety is primary, the authority having jurisdiction may be a federal, state, local, or other regional department or individual such as a fire chief; fire marshal; chief of a fire prevention bureau, labor department, or health department; building official; electrical inspector; or other having statutory authority.  For insurance purposes, an insurance inspection department, rating bureau, or other insurance company representative may be the authority having jurisdiction.  In many circumstances, the property owner or his or her designated agent assumes the role of the authority having jurisdiction; at government installations, the commanding officer or departmental official may be the authority having jurisdiction.


Automatic - (1) (Electrical) Self-acting, operating by its own mechanism when actuated by some impersonal influence, as, for example, a change in current, pressure, temperature, or mechanical configuration.  (2) As applied to fire-protection devices, is a device or system providing an emergency function without the necessity of human intervention and activated as a result of a predetermined temperature rise, rate of rise of temperature or increase in the level of combustion products.  (Reference:  2006 IRC, Chapter 34, ELECTRICAL DEFINITIONS, Section E3401, page 477)


Automatic Bleeder - An air bleeding apparatus commonly used with hot water base heating systems and steam heating systems, that eliminates the need to bleed the air-system by hand.


Automatic Door - A door equipped with a power-operated mechanism and controls that open and close the door automatically upon receipt of a momentary actuating signal.  The switch that begins the automatic cycle may be a photoelectric device, floor mat, or manual switch.


Automatic Expansion Valve - A pressure actuated metering device to regulate the flow of refrigerant into the evaporator according to the evaporator pressure.


Awning Window - An Awning Window is a window having a sash hinged on pins at the two top or bottom corners of the window frame, and which opens outward.   


Azeotropes - Refrigerants that are mixtures or blends of different refrigerants that are at the same ratio in vapor as well as in liquid state.


Azeotropes, Near - A zeotrope having a temperature glide sufficiently small that is inconsequential.


Azeotropic Mixture - A combination of different refrigerants to mask one with desirable refrigerant properties, an example of this is R-502 which is a mixture of 48.8% R-22 and 51.2% R-115.