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Construction Terms and Slang

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Valley Rafter
A rafter that forms the intersection of an internal roof angle. The valley rafter is normally made of double 2-inch-thick members.

Valve
A device to stop, start or regulate the flow of liquid or gas through or from piping.

Vapor
The gaseous form of any substance.

Vapor Barrier
Material used to retard the movement of water vapor into walls and prevent condensation in them. Usually considered as having a perm value of less than 1.0. Applied separately over the warm side of exposed walls or as a part of batt or blanket insulation.

Varnish
A thickened preparation of drying oil or drying oil and resin suitable for spreading on surfaces to form continuous, transparent coatings, or for mixing with pigments to make enamels.

Vehicle
The liquid portion of a finishing material; it consists of the binder (nonvolatile) and volatile thinners.

Veining
In roofing, the characteristic lines or "stretch marks" which develop during the aging process of soft bitumens.

Veneer
Thin sheets of wood made by rotary cutting or slicing of a log.

Vent
A pipe or duct which allows flow of air as an inlet or outlet.

Vent Pipe
A vertical pipe of relatively small dimensions which protrudes through a roof to provide for the ventilation of gasses.

Vent Stack
A vertical vent pipe installed for the purpose of providing circulation of air to and from any part of a drainage system.

Vent System
In plumbing, a system to provide a flow of air to or from a drainage system or to provide circulation of air within such system to protect traps seals from siphonage and back pressure.

Ventilator
Device installed on the roof for the purpose of ventilating the interior of the building.

Venting
The process of installing roof vents in a roof assembly to relieve vapor pressure. Also: The process of water in the insulation course of the roof assembly evaporating and exiting via the roof vents.

Vermiculite
An aggregate somewhat similar to perlite that is used as an aggregate in lightweight roof decks and deck fills. It is formed from mica, a hydrous silicate with the ability of expanding on heating to form lightweight material with insulation quality. Used as bulk insulation and also as aggregate in insulating and acoustical plaster and in insulating concrete.

Vidiot
(slang) Someone whose knowledge is limited exclusively to what he sees on television.

Viscosity
The internal frictional resistance offered by a fluid to change of shape or to the relative motion or flow of its parts.

Visible Light Transmittance
The percentage of visible light (390 to 770) nanometers) within the solar spectrum that is transmitted through glass.

Visual Mock-up
Small scale demonstration of a finished construction product.

Volatile Thinner
A liquid that evaporates readily and is used to thin or reduce the consistency of finishes without altering the relative volumes of pigment and nonvolatile vehicles

Voltage
The driving force behind the flow of electricity somewhat like pressure is in a water pipe.

Voltmeter
measures the voltage flowing through a circuit. The circuit must be closed to allow the voltage to flow.