VA loan: A home-loan guaranty for the purchase, building, repair, retention or adaptation of an owner-occupied home, with such benefit being insured by the U.S. Department of Veterans Affairs, a federal agency that extends various benefits and services to active service members and honorably discharged veterans (and their families) of the U.S. military.
vacuum breaker: An anti-siphon device that prevents wastewater from being drawn back into supply lines and potentially contaminating the water supply; a type of backflow preventer.
valley: The internal angle formed by the junction of two sloping sides of a roof.
valley flashing: Sheet metal or other material used to line a valley in a roof to direct rainwater down into the gutter system.
valley rafter: A rafter of double 2-inch-thick members that forms the intersection of an internal roof angle.
valley shield: A quality underlayment installed for added protection in the areas of a roof that experience heavy water flow. This self-adhering product has a waterproof asphalt coating that offers excellent elongation and recovery properties for accommodating roof expansion and contraction and structural movement.
valuation: An inspection carried out for the benefit of a mortgage lender to determine whether a property is adequate security for a loan.
valuation fee: The fee paid by a prospective borrower for the lender's required inspection of a property.
valve: A device to stop, start or regulate the flow of liquid or gas through or from piping.
vapor: The gaseous form of a substance.
vapor barrier: A a plastic or foil membrane that is placed between the insulation and the roof deck, as well as the ceiling, wall and floor assemblies, which resists the diffusion of water vapor from the building and into the insulation, where it may subsequently condense into liquid water and cause structural problems.
vapor diffusion retarder (vapor retarder): Any substance, including a treated paper or foil membrane, special paint or film that prevents the transmission of water vapor. Vapor diffusion retarders are effective for controlling moisture in basements, crawlspaces, and slab-on-grade foundations.
variable rate: An interest rate that varies over the term of a loan.
varnish: A thickened preparation of drying oil, with or without resin, that is suitable for spreading on surfaces to form a continuous, transparent coating, or for mixing with pigments to make enamels.
vehicle: The liquid portion of a finishing material that consists of the non-volatile binder and volatile thinners.
veining: In roofing, the characteristic lines that develop during the aging process of soft bitumens. Also, minor cracking that resembles spider veins occurs naturally during the curing process of cement. These cracks are normal and no cause for alarm, unless they grow, which would indicate a potential problem requiring further investigation.
veneer: A thin surface layer of wood or decorative brick facing that is overlaid and adhered as a façade to a base of inferior materials.
vent: A pipe or duct that permits the flow of air as an inlet or outlet; to create a vent or system of venting.
vent pipe: A vertical pipe of relatively small dimensions that protrudes through a roof to provide for the ventilation of gases or exhaust from various combustion systems or appliances, including a heater/furnace, clothes dryer, water heater, etc., as well as stale or damp air, odors, grease and contaminants, such as from a range, bathroom, attic, etc.
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 that provides air flow to or from a drain-waste-vent (DWV) system, or the circulation of air within such a system to protect traps and seals from siphonage and back-pressure.
ventilation: The natural or mechanical process of exchanging air in an interior space, and includes both the exchange of air to the outside, as well as the circulation of air within a building. It is one of the most important factors for controlling excessive moisture indoors and for maintaining acceptable indoor air quality.
ventilator: A device installed on a 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 by which water in the insulation course of the roof assembly evaporates and exits via the roof vents. See also vent and ventilation.
verify: To confirm or substantiate.
vermiculite: An aggregate similar to perlite that is formed from mica, a hydrous silicate, with the ability to expand upon heating to form a lightweight material with insulative qualities. Used in lightweight roof decks and deck infills, as well as bulk insulation, and as aggregate in acoustical plaster and concrete.
vertical: Upright; being or situated at a right angle to the horizon.
viscosity: The extent to which a fluid resists a tendency to flow.
visible: That which may be easily observed during the walk-through survey portion of an inspection.
visible light transmittance: The percentage of visible light within the solar spectrum (390 to 770 nanometers) that is transmitted through glass.
Visqueen: The brand name for a U.K.-based product of 4-mil to 10-mil plastic sheeting used as a groundcover and vapor barrier in the crawlspace of a home, a damp-proof course in a roof, a damp-proof membrane for exterior walls, a protective tarpaulin over setting concrete, and a waterproof membrane to line decorative ponds.
visual mock-up: A small-scale model of a finished construction product or project.
vitreous China: A non-porous ceramic that is coated with a ceramic glaze to form toilets and lavatories.
void: A rectangular cardboard box that is installed between the earth (between caissons) and a concrete foundation wall in the presence of expansive soils.
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 non-volatile vehicles.
voltage: The driving force behind the flow of electricity, similar to the pressure in a water pipe. Most U.S. homes are wired with 110- and 220-volt lines, with the 110-volt power used for lighting and most of the other circuits, and the 220-volt power used for the refrigerator/freezer, stove, water heater, clothes washing machine and dryer, and similar large household appliances.
voltmeter: A device that measures the voltage flowing through a circuit.