Architectural and Engineering Glossary


Activated Alumina

A form of aluminum oxide which adsorbs moisture readily and is used as a drying agent.

Activated Carbon

See activated charcoal.

Activated Charcoal, Activated Carbon

Charcoal obtained by carbonizing organic material,usually in the absence of air;usually in granular or powdered form;highly effective in adsorbing odors in air or in removing colors in solution.

Activated Rosin Flux

A flux having a resin or rosin base and containing an additive to increase wetting by the solder.

Activated Sludge

Sewage sediment that has been subjected to vigorous aeration and the action of microorganisms.


Same as catalyst.

Active Door

In a pair of doors, the leaf,1 that is the first to open and is the leaf to which a lock is applied.

Active Earth Pressure

The component of pressure in a horizontal direction which a mass of earth exerts on a wall.

Active Lateral Pressure

The horizontal soil pressure which is exerted by soil on a retaining structure.

Active Leaf,active Door

In a door having a pair of leaves,that leaf to which the latching or locking mechanism is attached;usually the leaf that is permitted to open first;sometimes both leaves are active.

Active Sludge

A sludge,3 which is rich in destructive bacteria;useful in breaking down fresh sewage.

Active Solar Energy System

A building subsystem in which solar energy is collected and is transferred predominantly by mechanical equipment (fans,pumps) powered by energy not derived from solar radiation.Compare with passive solar energy system.

Active Sound Attenuator

A special type of sound attenuator that incorporates a sound source which generates sound waves intended to cancel some of the noise generated by the fans in an HVAC system.


In CPM terminology,a task or item of work that must be performed in order to complete a project.

Activity Duration

In CPM terminology,the amount of time estimated as required to accomplish an activity.

Actual Start Of Construction

The first placement of permanent construction of a building on a site,such as pile driving,or the pouring of slabs or footings.


Finished in a point,as a lofty Gothic roof.

Acute Angle

An angle of less than 90.

Acute Arch, Lancet Arch

A sharply pointed arch whose centers are farther apart than the width of the arch.


1.Abbr. for “air dried.” 2.Abbr. for  access door.3.Abbr. for area drain.4.Abbr.for “as drawn.”


Abbr.for Americans with Disabilities Act. 

Adam Revival

See Colonial Revival.

Adam Style

An architectural style based on the work of Robert Adam (1728–1792) and his brothers,predominant in England in the late 18th century and strongly influential in the US,Russia,and elsewhere.It is characterized by clarity of form,use of color,subtle detailing,and unified schemes of interior design.Basically Neoclassical,it also adapted Neo-Gothic,Egyptian,and Etruscan motifs.

Adamesque Style

An inexact term implying a derivation from the Adam style,but having possible differences depending on the time and location of application.


To make suitable for a particular purpose or new requirements or conditions,by means of modifications or changes.


The capacity of building spaces and elements for being altered or being added to for specific needs,as,for example,to accommodate the needs of persons with and without disabilities. 


According to the ADA,a restroom or bathroom to which grab bars can be added or which can be otherwise altered to accommodate the needs of individuals with disabilities.

Adaptable Dwelling Unit

One of a number of dwelling units that is on an accessible route and equipped so it may be converted to be used,with a minimum of structural change,by all categories of physically disabled persons.


The process by which the eye changes sensitivity and becomes accustomed to more or less light than it was exposed to during an immediately preceding period.


1.A device for matching and properly connecting items,tubing,or devices (especially electric) which are of different size,operating characteristics,or design.2.A device that enables different sizes or types of plugs,pipes,etc.,to be joined.

Adaptive Use,adaptive Re Use

The extensive alteration,restoration,and/or renovation of an existing building so that it will serve a new or modified purpose.Also see building rehabilitation.


Abbr.for “Air Diffusion Council.”


1.On drawings,abbr. for addendum.2.On drawings,abbr. for addition.


lean to Same as integral lean to.


A written or graphic instrument issued prior to the execution of the contract which modifies or interprets the bidding documents,including drawings,and specifications,by additions,deletions,clarifications or corrections;becomes part of the contract documents when the construction contract is executed.


1.A floor or floors,a room,wing,or other expansion  to an existing  building.2.In building code usage:Any new construction which increases the height or floor area of an existing building or adds to it (as a porch or attached garage).3.An amount added to the contract sum by a charge order;also see extra.

Additional Service Authorization

An AIA form that authorizes additional work,1 to be performed,for an additional fee,for services not covered in the originally specified scope of the architect’s work.

Additional Services

The professional services which may,upon the owner’s request or approval,be rendered by the architect in addition to the basic services or the designated services.


A material,used in very small quantity,to modify a specific property of another material or otherwise improve its characteristics;used in paints,plasters,mortars, etc.

Additive Alternate

An alternate bid resulting in an addition to the same bidder’s base bid.Also see alternate bid.

Additus Maximus

In an ancient Roman amphitheater,a main entrance.


Said of animals or figures placed back to back in decorative sculpture.

Addressable System

A fire alarm system whose integrity can be monitored and which provides easy identification of the location of an alarm condition;also provides for remote testing and monitoring of the sensitivity of the detectors from a control panel.


In the lumber industry,abbr.for “after deducting freight.”


On drawings,abbr.for adhesive.


A body which is held to another by an adhesive.


1.The joining of two surfaces as pieces of wood,metal,plastic,or other construction materials,by means of a viscous,sticky composition such as cement or glue.2.Thesticking together of two surfaces by means of physical and chemical forces such as those which bind a paint film to a surface.

Adhesion Bond

The adhesion of mortar or grout to masonry units.

Adhesion Type Filter

A type of air filter in which dirt particles are removed from air by adhering to the filter as the air flows through it. 

Adhesion-type Ceramic Veneer

Thin sections of ceramic veneer held in place by the adhesion of mortar to unit and backing,requiring no metal anchors;not more than 11⁄4  in. (3.2 cm) in overall thickness.Also see anchored type ceramic veneer.