Architectural and Engineering Glossary

Backfilling, Backfill

1.Rough masonry built behind a facing or between two faces. 2.Filling over the extrados of an arch. 3.Brickwork in spaces between structural timbers. Also see nogging.4.Soil or crushed stone used to fill the space between the excavation or sheeting and the exterior of a structure, or around the founda- tion walls to provide means for water to drain away from a foundation.

Backflap Hinge, Flap Hinge

A hinge having a flat plate or strap which is screwed to the face of a shutter or door.


1.The flow of water or other liquids, mixtures, or substances into the distributing pipes of a potable supply of water from any other than its intended source. Also see back siphonage.2.Any flow in a direction opposite to the  natural or intended  direction of flow.

Backflow Connection

Any arrangement of pipes, plumbing fixtures, drains, etc., in which backflow can occur.

Backflow Preventer

A device used to prevent water (or other liquids) from being siphoned into a potable water system.

Background Noise

The total noise from all sources other than a particular one of interest. 


An excavating machine for cutting trenches; a boom mounted bucket moves toward the machine, cutting the ground like a hoe; then the machine turns away from the cut to permit the operator to dump the soil.

Backhouse, Back Building

1.A privy or outhouse.2.A structure that stands behind a building to which it is a subsidiary.

Backing Board

In a suspended acoustical ceiling, a flat sheet of gypsum board to which acoustical tile is attached by adhesive or mechanical means.

Backing Brick

A relatively low quality brick used behind face brick or other masonry.

Backing Coat

A coat of plaster other than the finish coat.

Backing Ring

A backing in the form of a ring, used during the welding of piping at butt joints. 

Backing Up

In masonry, the laying of backing brick.


In masonry, a rabbet such as that made on the inner side of a chimneypiece to receive a slip.


The illumination of an object from the rear.


A coat of plaster applied to the back side of lath, opposite the finished surface.


A plate, usually metal or wood, which serves as a backing for a structural member.

Backplate Lamp Holder

A lamp holder, integrally mounted on a plate, which is designed for screwing to a flat surface.


A saw having a metal strip along its back to stiffen it; has many small teeth for fine, accurate sawing, as for miters.


1.The horizontal distance from the face of a lock or latch to the center of the key hole, knob, or lock cylinder. 2.Same as set back.


 In surveying, a sight on a previously established survey point or line.


A protective panel on the wall behind a sink or counter;an apron,7.


The entire area behind the fire wall of the stage of a theater,including therear of the stage,storage areas,and dressing rooms.


1.That part of a masonry wall behind the exterior facing.2.A compressible material used behind a sealant to reduce its depth and to support the sealant against sag or indentation.3.Overflow in a drain or piping system,due to stoppage.4.A condition where waste water flows back into another fixture or compartment or water line (but does not flow back into the potable water system).

Backup Protection

In an electrical system,a type of protection initiated by a sensing device that detects a failure of a protective element (such as a circuit breaker);in that event, the next upstream protective device takes over the protective function.

Backup Rod

A strip of plastic foam that is inserted in a joint to limit the penetration of sealant into the joint.

Backup Strip

A piece of wood at the corner of  a ceiling and side wall;serves as the mounting for the ends of the gypsum board panels.

Backup Strip,lathing Board

A wood strip which is fixed at the corner of a partition or wall to provide a nailing surface for ends of lath.

Backwater Valve, Backflow Valve

A type of check valve in a drainage pipe;reversal of flow causes the valve to close,thereby cutting off flow.

Bacterial Corrosion

A corrosion which results from substances (e.g., ammonia or sulfuric acid) produced by the activity of certain bacteria.


1.A tool used inside a pipe or culvert to remove excess mortar or deposits.2.A badger plane.

Badger Plane

A hand plane,the mouth of  which is cut obliquely from side to side,so that it can work close up to a corner.


A filler or patching material used in masonry or wood work.


1.A plate used to control the flow of a liquid.2.An opaque or translucent plate used to shield a light source from direct view at certain angles;a light baffle.3.A flat deflector or obstruction designed to reduce sound transmission.4.A plate that retards and/or changes the direction of the flow of air,air gas mixtures,or flue gases.

Bag Molding

The application of pressure on a material during molding so that it takes the shape of a curved,rigid die.The material,contained within the die and a flexible cover,is deformed by changes of pressure within the enclosure.

Bag Plug

An inflatable drain stopper;when inflated,it acts to seal a pipe;usually located at the lowest point of the piping system.

Bag Trap

An S-shaped trap,1 in which the vertical inlet and outlet pipes are in alignment.

Bag-rubbed Joint

Same as flush cut joint.


A quantity of portland cement:94 lb in the United States,87.5 lb in Canada,112 lb (50.8 kg) in the United Kingdom,and 50 kg in most countries using the metric system.


A by product of sugar cane after the juice has been extracted;used as a fuel and also as the principal component in cellulose cane acoustical tile.

Bagged Brickwork

Brickwork that is prepared for painting by applying a thin mixture of water and mortar to the brickwork,such as by pounding the brickwork with a burlap (Hessian) bag containing the mixture.


A bead molding.


1.A bathing establishment.2.A brothel.2. A Turkish prison.


An annular molding encircling the shaft of a column or pillar,either half way between the base and capital or at lesser intervals.


A small,convex molding.


1.In a masonry wall or parapet,the rounded upper course.2.A low wall surmounting a cornice to carry the roof structure.


A box in a theater in the lowest  tier.


1.The wall of an outer court of a feudal castle.2.A hinged loop that is used for lifting.


The open area within a castle fortification.See inner bailey and outer bailey;also see motte and bailey.


A wattle and daub wall constructed of bagasse,which is covered with plaster mixed with clay and straw.