Architectural and Engineering Glossary

Vapor Lock Device

Any device,such as an orifice or capillary tube,which eliminates or minimizes the collection of vapor in a pipe.

Vapor Migration

The movement of water vapor as a result of a vapor pressure differential between a building roof or walls and the outside,resulting in vapor penetration.

Vapor Permeance

See permeance.

Vapor Pressure

The component of the total pressure which is caused by the presence of a vapor,as,for example,by the presence of water vapor in air.

Vapor Resistance

The resistance to the flow of water vapor;the reciprocal of permeance.

Vapor Retarder

1.A membrane covering the outer surface of an insulated cold water pipe that is used to prevent moisture from penetrating the insulation and reaching the pipe.2.A layer of material or laminate used to reduce,appreciably,the flow of water vapor into a roofing system.

Vapor Transmission

See water vapor transmission.

Vapor Vent, Vapor Relief Vent

Same as local vent.


Said of a surface that is enclosed so as to resist the passage of vapor,often including the use of a gasket around its periphery.


See vapor.

Variable Air Valve (VAV)

In an HVAC system,a control unit consisting of a metal box containing damper position control equipment,a controller,and a sensor.The box is usually supplied with “primary” air through a duct from the main distribution system;the output delivers air to diffusers located in the space being served.

Variable-volume Air System

An air-conditioning system in which the quantity of air supplied to each controlled zone is regulated automatically,from some preset minimum value to a maximum value based on the load in each zone.


A written authorization,from the responsible agency,permitting construction in a manner which is not allowed by code or other regulations.

Variation Order

British term for change order.variegated Said of material or a surface which is irregularly marked with different colors;dappled.varnish A clear,unpigmented preparation consisting of resinous matter dissolved in alcohol (spirit varnish) or other volatile liquid,or in oil (oil varnish);when applied as a thin coating on a surface,it dries leaving a hard,smooth,transparent,glossy protective film.

Varnish Drier

See drier.

Varnish Remover

A material,usually liquid,which softens or dissolves a dry film of varnish so that it can be removed easily.

Varnish Stain

A varnish which is colored with a transparent material,leaving a colored coating on the surface;has less penetrating power than a true stain.

Varved Clay

Alternating thin layers of silt (or fine sand) and clay formed by variations in sedimentation during the various seasons of the year,often exhibiting contrasting colors when partially dried.


See wat.


1.A structure based on the  principle  of the arch,often constructed of masonry;typically consists of an arrangement of arches that cover the space below;also see barrel vault, cradle vault,cylindrical vault, fan vault,groined vault,lierne vault,rampant vault,ribbed vault, segmental vault,sidewalk vault,stilted vault,tunnel vault,wagon vault,Welsh vault.2.A burial chamber,especially one under a church. 3.An underground chamber especially designed for maintaining electrical equipment.4.A room for the safekeeping of valuables.

Vault Bay

An area of vaulting limited by two transverse ribs;a severy.

Vault Door

A factory assembled door with a frame and hardware which are designed to protect a storage room against fire and/or burglars.

Vault Light

Same as pavement light.

Vault Rib

An arch under the soffit of a vault that seems to support it.

Vault Shell

The web plates between the ribs of the vault that are, or seem to be,supported by them.

Vault Springing

The point where the ribs of a vault rise upward from an arch impost,capital,or corbel.


1.Constructed as a vault. 2.Covered or closed by a vault.


1.Vaulted work.2.Vaults,collectively.

Vaulting Boss

A boss,1 set at intervals in a ribbed vault,at a junction between the ribs.

Vaulting Capital

The capital of a pier or colonette intended to support a vault or a rib thereof.

Vaulting Cell

One compartment of a vault which is so planned that one part can be built at a time.

Vaulting Course

A horizontal course made up of the abutments or springers of a vaulted roof.

Vaulting Shaft

A colonette in a membered pier that appears to support a rib in a vault.

Vaulting Tile

A special type of hollow tile,shaped according to the specific job;used in vaulting to reduce the weight of the upper parts of large masses of masonry.


Abbr. for “video display terminal.”


 Abbr. for “visual display unit.”

Vebe Apparatus

An apparatus for measuring the consistency of freshly mixed concrete;determined from a measurement of the time for a vibrated,truncated cone to be transformed into a right cylinder.


See V-.


See V-joint.

Vegetable Black

Same as lampblack.

Vegetable Glue

A water based treated starch which spreads easily;has low strength and poor moisture resistance;esp.used for hanging wall paper.

Vegetable Oil

An oil extracted from vegetable matter;esp.castor,linseed,safflower,soya,and tung oil;used in paints and plastics.


In a paint,the liquid in which the pigment is dispersed.

Vehicular Way

A route intended for vehicular traffic,such as along a street.

Vein Cut

Quarried stone that is cut perpendicular to its natural bedding plane.


The awning sheltering the seats in an ancient Roman theater or amphitheater from sun and rain.

Vellum Glaze

A semimatte glaze having a satin like appearance.

Velocity Head

Of a fluid moving with a given velocity:the equivalent height through which a body must fall to acquire the same velocity.


A stadium or arena with a banked track designed for bicycle or motorcycle racing.


Same as velarium.