V

vaneaxial fan 1. A fan consisting of a disk-type wheel within a cylinder, with a set of air guide vanes located either before or after the wheel; may be either belt-driven or connected directly to a motor. 2. An axial-flow fan which incorporates downstream guide vanes. It has a higher efficiency than any other type of axial-flow fans.

vaned outlet A register or grille which is equipped with vertical and/or horizontal adjustable vanes to regulate the direction of airflow.

vane ratio The ratio of the depth of a vane, 2 to the minimum distance between adjacent vanes.

vanishing point In perspective, a point toward which a series of parallel lines seem to converge.

vanity In a bathroom, a combination lavatory and base cabinet.

VAP On drawings, abbr. for “vapor.”

vapor barrier See vapor retarder.

vapor heating system A steam heating system which operates at or near atmospheric pressure and returns the condensate to the boiler or receiver by gravity.

vapor lock The formation of vapor in a pipe carrying liquids; prevents normal fluid flow.

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-tight 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.

vapor transmission See water vapor transmission.

vapor vent, vapor relief vent Same as local vent.

vapour 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.

variance 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, trans parent, 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.

vase See bell, 1.

vat See wat.

VAT Abbr. for vinyl-asbestos tile.

vault 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.

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

vaulting 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.

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.

V-beam sheeting Similar to corrugated sheeting but formed of a series of angled flat surfaces instead of curved surfaces.

V-brick Vertically perforated brick.

V-cut 1. Descriptive of lettering, inscribed in stone, in which the cuts are acutely triangular. 2. Any saw cut or cut in wood which is V-shaped.

VDT Abbr. for “video display terminal.”

VDU 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.

vee-joint 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 wallpaper.

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

vehicle 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.

velarium 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.

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

velum Same as velarium.

velvet carpet Carpet woven on a loom in a manner similar to cloth; the layers of pile yarn loops are bound to a layer of jute; then the pile is cut, forming a smooth surface.

vendor 1. A person or organization who furnishes materials or equipment not fabricated to a special design for the work, 1. Also see supplier. 2. One who sells or contracts to sell real property. Also see purchaser.

veneer 1. A thin sheet of wood that has been sliced, rotary-cut, or sawn from a log; often used as the top one of several layers of plywood serving as a facing that is bonded to a less attractive wood, or as facing on a fire-rated material. 2. An outside wall facing of brick, stone, etc.; provides a decorative, durable surface but is not load-bearing. 3. See brick veneer.

veneer base A type of gypsum lath sheeting, usually 4 ft (121.9 cm) wide, available in various thicknesses and lengths; has a gypsum core with a special paper facing which permits veneer plaster to be applied.

veneered construction A reinforced concrete or steel framework (or wood construction) which is faced with a thin external layer of marble, structural glass, or some other facing material.

veneered door A door made up of either a solid or a hollow core and veneer faces.

veneered plywood Plywood which is faced with a decorative wood veneer.

veneered wall A wall of veneered construction. For example, a wall having a facing of brick or some other weather-resistant noncombustible material that is securely attached to the backing, but not bonded to it.

veneer plaster A one-component or two-component mill-mixed gypsum plaster; applied to a maximum overall thickness of about

in. (0.25 cm); has good bond, high strength; is rapidly installed.

veneer tie A wall tie designed to hold a veneer facing to the wall construction.

veneer wall, veneered wall Any wall having a facing which is attached, but not bonded, to the wall. Also see brick veneer.

veneer wall tie A strip of metal used to tie a facing veneer to the wall which it covers.

Venetian, Venetian mosaic A type of terrazzo topping containing large chips.

Venetian arch A pointed arch in which the intrados and extrados are farther apart at the peak than at the springing line.

Venetian blind 1. A blind, 1 made of thin horizontal slats or louvers, so connected as to overlap one another when closed, and to show a series of open spaces for the admission of light and air when open; esp. a hanging blind of which the slats are held together by strips of webbing or other flexible material. 2. Adjustable exterior slatted shutters.

Venetian dentil A type of dentil; a notched ornamentation consisting of a series of cubical projections alternating with sloped surfaces.

Venetian door A door having a long narrow window at each side which is similar in form to that of a Venetian window.

Venetian Gothic Same as High Victorian Gothic.

Venetian mosaic See Venetian.

Venetian motif See Palladian motif.

Venetian red A red pigment having a high red iron oxide content.

Venetian window, Palladian window, Diocletian window A window of large size, characteristic of neoclassic styles, divided by columns or piers resembling pilasters, into three lights, the middle one of which is usually wider than the others, and is sometimes arched.

vent 1. A pipe installed to provide a flow of air to or from a drainage system or to provide a circulation of air within such system to protect trap seals from siphonage and back pressure. 2. A vent connector. 3. A vent system. 4. A ventilator, 3. 5. A stack designed to allow moisture vapor or other gas from inside a building or building system to escape into the atmosphere. 6. See cavity vent.

VENT. On drawings, abbr. for “ventilate.”

vent cap A fitting which provides protection for the open end of a vent stack, soil stack, or waste stack; prevents objects from being dropped down the stack.

vent connector A metal pipe which connects the exhaust of a gas appliance to a chimney.

vented form Formwork constructed to retain the solid constituents of concrete but to permit water and air to escape.

vented wall furnace A recessed heater; a self-contained vented appliance designed for incorporation in, or permanent attachment to, the structure of a building.

vent extension A pipe from the uppermost drainage branch connection through the roof to the atmosphere.

vent flue Same as vent, 1.

vent header A header, 4 (i.e., a horizontal vent pipe) that connects the tops of vent stacks or stack vents at the header; a single vent pipe extends from the header to the open air above the roof.

ventilated ceiling A ceiling containing a multiplicity of air outlets covering a significant part of the ceiling area and acting as a whole (not as individual units).

ventilating bead See draft bead.

ventilating brick A brick with holes in it to provide for air passage.

ventilating eyebrow Same as eyebrow window.

ventilating jack A sheet-metal hood over the inlet to a vent pipe to increase the flow of air into the pipe.

ventilation The process of supplying or removing air, by natural or mechanical means, to or from any space; such air may or may not have been conditioned.

ventilation pipe Same as vent pipe.

ventilator 1. In a room or building, any device or contrivance used to provide fresh air or expel stale air. See ridge ventilator, roof ventilator, and slit ventilator. 2. A framework, pivoted on hinges, in which panes of glass are set; a pivoted sash. 3. Same as ventlight.

ventilator frame An assembly consisting of two rails and two stiles, designed to support the glass of a pivoted sash (ventilator, 2).

venting The replacement of air that is carried out from a stack into the building drain and sewer by waste.

venting loop Same as loop vent.

ventlight, night vent, vent sash In a window, a small operable light (pane) with hinges along its upper edge, so that it may be swung open to provide ventilation without opening the entire sash.

vent pipe 1. A pipe, attached to drainage pipes near one or more traps, which leads to outside air (e.g., a connection to a vent stack); admits air or takes air away from the drainage pipes and prevents the trap seals from being broken by air pressure within the drainage pipes. 2. A pipe connecting a space on the interior of a building with outside air.

vent sash Same as ventlight.

vent stack, main vent A vertical vent pipe installed primarily for the purpose of providing circulation of air to or from any part of the building-drainage system, and to prevent the water seals of the traps from being broken by siphonage.

vent system A gas vent or chimney, together with a vent connector, that forms a continuous unobstructed passageway from gas-burning equipment to the outdoor air for the purpose of removing vent gases.

veranda, verandah An open porch or balcony, usually covered, that extends along the outside of a house or other building; sometimes called a piazza; also see galerie and galería.

verd antique, verde antique A dark green serpentine rock marked with white veins of calcite; takes a high polish; used for decorative purposes since ancient Rome; sometimes classed as a marble.

verdigris, aerugo The greenish blue corrosion on copper that has been exposed to air for a long period of time; used as a pigment.

verge 1. The edge projecting over the gable of a roof. 2. The shaft of a column; a small ornamental shaft.

vergeboard Same as bargeboard.

verge course See barge course.

verge fillet A strip of wood nailed to the roof battens over a gable; covers the upper edges of the gable walls.

verge rafter See barge couple, 2.

verge tile A tile at the edge of a roof, projecting over the gable; usually somewhat wider than the other tiles on the roof.

vermiculated Ornamented by irregular winding, wandering, and wavy lines, as if caused by the movement of worms.

vermiculated mosaic An ancient Roman mosaic of the most delicate and elaborate character; the Roman opus vermiculatum; the tesserae are arranged in curved, waving lines, as required by the shading of the design.

vermiculated work 1. A form of masonry surface, incised with wandering, discontinuous grooves resembling worm tracks. 2. A type of ornamental work consisting of winding frets or knots in mosaic pavements, resembling the tracks of worms.

vermiculite A natural mica expanded by heat (i.e., exfoliated) to form lightweight thermal insulating material, used in the expanded state alone as loose-fill or as aggregate with other materials.

vermiculite concrete Concrete in which the aggregate consists of exfoliated vermiculite.

vermiculite plaster A plaster using very fine exfoliated vermiculite as the aggregate; used as a fire-retardant covering on steel beams, concrete slabs, etc.

vernacular architecture Architecture that makes use of common regional forms and materials at a particular place and time; sometimes includes strong ethnic influences of an immigrant population; usually modest, unassuming, and unpretentious, and often a mixture of traditional and more modern styles or a hybrid of several styles. Houses are often owner-built by people familiar with local materials, regional climatic conditions, and local building customs and techniques, as described under folk architecture.

vernier An auxiliary scale sliding against and used in reading a primary scale; the total length of a given number of divisions on a vernier is equal to the total length of one more or one less than the same number of divisions on the primary scale; makes it possible to read a principal scale much closer than one division of that scale.

versurae The side wings of the stagehouse of an ancient Roman theater.

VERT On drawings, abbr. for “vertical.”

vertical 1. Any upright member, as in a truss. 2. The direction of gravity, at right angles to the horizon.

vertical angle An angle in a vertical plane.

vertical bar An upright muntin.

vertical blind A blind, 1, in a window, comprised of thin vertical slats that can be adjusted to darken a room or block a view.

vertical bond Same as stack bond.

vertical circle A graduated disk mounted on an instrument in such a manner that the plane of its graduated surface can be placed in a vertical plane.

vertical curve A smooth parabolic curve in the vertical plane used to connect two grades of different slope to avoid an abrupt transition in passing from one to the other.

vertical cut Same as plumb cut.

vertical diaphragm Same as shear wall.

vertical exit Any path of travel such as a stair, ramp, escalator, or fire escape, serving as an exit from the floors above or below the street floor.

vertical-fiber brick A type of paving brick which is cut with a wire in manufacture; laid with wire-cut side facing up.

vertical firing In a furnace, burners (gas, oil, or pulverized-coal) which are arranged so that the fuel is discharged vertically—either upward from burners below or downward from burners in the top.

vertical-grained See edge-grained.

vertical-log cabin A log cabin whose exterior logs are oriented vertically rather than horizontally; this construction requires more time and greater skill than if the logs are oriented horizontally, as is usual. For an example of construction in which vertical logs are driven in the ground, see poteaux-en-terre; also see poteauxsur-sole, a somewhat similar construction where the vertical logs rest on a wood foundation.

vertically pivoted window, reversible window A window having a sash (ventilator, 2) which pivots (usually 360°) about a vertical axis at or near its center; when opened, the vertically pivoted window outside glass surface is conveniently accessible for cleaning.

vertical meeting rail See meeting stile.

vertical opening An opening through a floor, roof, or other horizontal surface.

vertical pipe Any pipe or fitting which makes an angle of 45° or less with the vertical.

vertical plane A plane at right angles to the horizontal plane and within which angles and distances are observed.

vertical-plank door Same as battened door.

vertical pump A long, slender multistage pump designed primarily to pump water from deep wells.

vertical riser diagram Same as riser diagram.

vertical sash Same as vertical sliding window.

vertical saw A saw which operates in a vertical plane.

vertical section A drawing depicting a view that would be seen if a vertical plane were cut through the object observed.

vertical siding A type of exterior wall cladding attached to the wall in a vertical orientation; most often consists of wide, upright boards that have a tongue along one vertical edge and a groove along the opposite edge; also see siding and tongue-and-groove joint.

vertical sliding window A window having one or more sashes which move only in the vertical direction; they are held in various open positions by means of friction or a ratchet device instead of being supported by sash balances or counterweights.

vertical slip form A form which is jacked vertically and continuously during the placing of concrete.

vertical spring-pivot hinge A spring hinge for a door which is mortised into the heel of the door; the door is fastened to the floor and door head with pivots.

vertical tiling Tile which is hung vertically on the face of a wall; provides protection against moisture.

vertical transportation services Elevators, escalators, and other mechanical devices in a building for transporting people or goods from one level to another.

vertical tray conveyors A vertical conveying system which is capable of carrying trays or boxes.

vertical-vision-light door Same as narrow-light door.

very-high-output fluorescent lamp A rapid-start fluorescent lamp designed to operate on higher current than a high-output fluorescent lamp, providing a corresponding increase in light flux (lumens) per unit length of lamp.

vesica piscis A long and sometimes pointed oval form; a mandorla.

vestiary A room for the keeping of vestments, garments, or clothes; a wardrobe.

vestibule An anteroom or small foyer leading into a larger space.

vest-pocket park A park which is built on a small plot of land.

vestry, revestry A chamber in a church, near the sanctuary, for the storage of the utensils used in a service and for the robes of the clergy and choir.

VG Abbr. for “vertical grain.”

V-groove See quirk, 2.

V-gutter A valley gutter.

via de crujía The enclosed passageway between the high altar and choir of a Hispanic cathedral.

vibrated concrete Concrete compacted by vibration during and after placing.

vibrating pile driver Same as sonic pile driver.

vibrating roller A roller which has a motor-driven eccentric for compacting soils.

vibrating screed A machine designed to level a freshly poured concrete slab and also to act as a vibrator.

vibration As applied to concrete, see concrete vibration.

vibration isolator A resilient support for machinery, piping, ductwork, etc., which may act as a source of vibration; designed to reduce the amount of vibration transmitted to the building structure.

vibration limit The time required for fresh concrete to harden sufficiently to prevent its becoming mobile when subjected to vibration.

vibration meter An apparatus for measuring the displacement, velocity, or acceleration of a vibrating body.

vibration mount Same as vibration isolator.

vibration service lamp An incandescent lamp, having a tungsten filament, which is designed to withstand mechanical vibration to a greater degree than a general service lamp.

vibrator An oscillating, power-operated machine used to agitate fresh concrete so as to eliminate gross voids including entrapped air (but not entrained air) and to produce intimate contact with form surfaces and embedded materials.

vicarage In England, the home or residence of a vicar.

Vicat apparatus A penetration device used in the testing of hydraulic cements and similar materials to measure their consistency and their initial and final setting times.

vice See vis.

vice stair A screw stair.

Vickers number A numerical rating for the hardness of a metal; measured by applying a known force to an inverted pyramid-shaped diamond placed on the surface of the metal, and then measuring the area of indentation and the depth of penetration.

Victorian architecture 1. The Revival and Eclectic architecture in 19th century Great Britain, named after the reign of Queen Victoria (1837–1901); also its American counterpart. Many architectural historians avoid the term Victorian architecture, considering the adjective “Victorian” merely as descriptive of an age that encompassed a number of specific exuberant, ornate, and highly decorative architectural styles. 2. A loose term that sometimes covers three picturesque phases of architecture in America: Early Victorian (1840–1860), High Victorian (1860–1880), and Late Victorian (1880– 1890) and beyond; the adjective “Victorian” is descriptive of an age that encompassed a number of specific exuberant, ornate, and highly decorative architectural styles, such as High Victorian Italianate (1860–1885), High Victorian Gothic (1860–1890), Second Empire style (1855– 1890), Stick style (1860–1885), Shingle style (1880–1890), Victorian Romanesque (1870– 1900), Gingerbread Folk architecture (1870– 1910), and Queen Anne style (1870–1910). The adjectives Victorian or High Victorian are sometimes applied to Gothic Revival and Italianate style to indicate their later, more detailed, and more elaborate phases.

Victorian Gothic Same as High Victorian Gothic; also see Gothic Revival.

Victorian Queen Anne style See Queen Anne style.

Victorian Romanesque An ornate outgrowth of the Richardsonian Romanesque style from which it differs both in the use of color and in the texture of masonry, and in being less exact in adapting Romanesque style forms; popular from about 1870 to 1900; usually characterized by: rock-faced stone or decorative stonework, often polychromed; brick of different colors; panels of terra-cotta; semicircular arches or compound arches similar to those in the Romanesque style; pilastered arcades at ground level; steeply pitched wall gables; multicurved parapets; window heads framed by masonry arches; doors set within concentric rounded masonry arches or with voussoirs of more than one color.

Vierendeel truss, Vierendeel girder An open-web truss having verticals which are rigidly connected to the top and bottom chords but without diagonals.

viga In Spanish Colonial architecture and its derivatives, a log that has been stripped of its bark and unhewn; used as one of a number of roof beams spanning the width of a building between opposite adobe walls; usually evenly spaced along the length of the walls; often round in cross section. Typically, the vigas are overlaid with small straight saplings that are covered by a reed matting; this combination supports a roof of dried mud or adobe.

vignette See vinette.

vihara A Buddhist or Jain monastery in Indian architecture.

Viking style See Dragon style.

villa 1. In the Roman and Renaissance periods, a country seat with its dwelling, outbuildings, and gardens, often quite elaborate. 2. In modern times, a detached suburban or country house of some pretension.

village green An open space or public park, once traditionally located at the center of a village; still found in many towns today; also see common.

Villa style See Italianate style.

vimana 1. A Hindu temple, mainly of the Deccan and southern India. 2. The sanctuary in such a temple containing a cell in which a deity is enshrined.

vine A plant whose stem is not self-supporting.

vinette, trayle, vignette An ornament of running vine scrolls with grape clusters and leafwork.

vinyl A thermoplastic compound made from polymerized vinyl chloride, vinylide chloride, or vinyl acetate; includes some plastics made from styrene and other chemicals.

vinyl-asbestos tile A resilient, semiflexible floor tile; composed of asbestos fibers, ground limestone, plasticizers, pigments, and a polyvinyl chloride resin binder; has good wearing qualities, high grease resistance, and relatively good resilience.

vinyl composition tile A resilient floor covering which is composed of a binder (one or more resins, such as vinyl chloride, compounded with suitable plasticizer and stabilizers) with fillers, and pigment.

vinyl flooring A resilient floor covering in sheet or tile form composed of a vinyl plastic binder, mineral fillers, and pigment.

vinyl paint A water-based paint containing vinyl.

vinyl tile A floor tile composed principally of polyvinyl chloride but also containing mineral fillers, pigments, plasticizers, and stabilizers; does not require waxing; usually set in mastic over a wood or concrete subfloor.

Virginia house A comparatively simple timber-framed wood house used during the 17th century, originating in the Chesapeake Bay area of the Commonwealth of Virginia; supported by posts sunk in the ground rather than by a foundation. The exterior walls were covered with a wall cladding of hand-split clapboards, which provided additional structural strength.

Virginia I-house An I-house often found in southern US; usually has a relatively low-pitched roof, a central dormer, and a raised foundation.

Virginia rail fence Same as zigzag fence.

vis, vice, vise A spiral staircase generally of stone, whose steps wind around a central shaft or newel; a screw stair.

viscometer A device for determining viscosity; esp. used to measure the viscosity of slurries, including fresh concrete.

viscosimeter Same as viscometer.

viscosity The internal frictional resistance exhibited by a fluid in resisting a force which tends to cause the liquid to flow.

viscous filter A filter for cleaning air; dirt, carried by the air, impinges on a surface covered with a viscous fluid or oil, to which the dirt particles adhere.

vise 1. A gripping tool, fixed or portable, used to hold an object firmly while work is performed on it; has movable jaws, similar to a clamp, which are brought together by a screw or lever. 2. See vis.

visibility 1. The quality or state of being perceivable by the eye. 2. The distance at which an object out-of-doors can be just perceived by the eye. 3. The size of a standard test object, observed under standardized viewing conditions, which has the same threshold as the given object.

vision cloth A curtain on the stage of a theater which has a gauze or scrim inset; if an actor (or scene) behind the inset is illuminated, he is visible to the audience as one appearing in a vision.

vision light 1. A window glazed with clear glass for viewing. 2. A viewing window in a fire-rated door; usually wire glass must be used and the dimensions of the glass are limited by code.

vision-light door A door having one small viewing window in the upper portion only, usually located on the vertical center line of the door.

visionproof glass See obscure glass.

visitá In Spanish Colonial architecture in the American Southwest, a chapel in which services were conducted by a visiting padre because it served too few people to have its own priest.

visor roof A pent roof, 1 that extends only along one face of a building, usually the façade.

vista A usually unobstructed view into the distance; often given scale by the receding perspective of a road or a row of trees.

visual acuity A measure of the ability to distinguish fine details; the reciprocal of the angular size of critical detail which is just large enough to be seen.

visual angle The angle which an object or detail subtends at the point of observation; usually measured in minutes of arc.

visual field The angular extent of space which can be perceived when the head and eyes are kept fixed.

visual inspection Inspection by examination without the use of testing apparatus.

visual photometer See photometer.

VIT On drawings, abbr. for “vitreous.”

vitreous Descriptive of that degree of vitrification evidenced by low water absorption; generally signifies less than 0.3% absorption (except for floor and wall tile and low-voltage electrical porcelain, for which it signifies less than 3.0% absorption).

vitreous china A ceramic that is glazed, vitrified, and extremely smooth.

vitreous enamel See porcelain enamel.

vitreous sand Same as smalt.

vitreous tile Same as glazed tile.

vitrification Of a clay product, the condition resulting when kiln temperatures are sufficient to fuse grains and close the surface pores, making the mass impervious.

vitrified Same as vitreous.

vitrified brick Brick which has been glazed so that it is impervious to water and has a high resistance to chemical corrosion.

vitrified-clay pipe Pipe manufactured of an earthenware material which is glazed so that it is impervious to water and has a high resistance to chemical corrosion; in the US, sometimes used for house sewer pipes and underground drainage.

vitrified sewer pipe See vitrified-clay pipe.

Vitruvian scroll, Vitruvian wave A common motif in classical ornament: a series of scrolls connected by a wave-like band; also called a wave scroll or running dog.

vivarium An enclosure for raising animals and keeping them under observation.

V-joint, vee-joint A recessed masonry joint, formed in mortar by the use of a V-shaped metal tool.

V-notch A notch, in the shape of the letter V, cut into a log or timber near one of its ends; forms a rigid joint when mated with another appropriately notched log or timber in log-cabin or log-house construction.

void-cement ratio The ratio of volume of air plus water to the volume of cement.

void ratio In a soil mass, or the like, the ratio of the volume of the void space to the volume of the solid particles.

voids 1. In cement paste, mortar, or concrete, the air spaces between and within pieces of aggregate. 2. Volumes of air not occupied by the solid material of a soil; voids usually are partially filled with air and water.

void-solid ratio The proportion of window and door openings to wall surface area in the exterior wall of a building.

VOL On drawings, abbr. for “volume.”

volatile Descriptive of a substance which passes off easily as a gas or vapor, evaporating quickly.

volatile thinner A thinner which evaporates especially rapidly, reducing the viscosity of a paint, adhesive, etc., without altering its other properties.

volcanic tuff See tuff.

volt In electric systems the unit of potential difference or electromotive force; when applied across a resistance of 1 ohm, will result in a current flow of 1 ampere.

voltage Of an electric circuit, the greatest root-mean-square difference of potential between any two conductors of the circuit.

voltage drop The difference in electromotive force between any two points in an electric circuit.

voltage regulator An automatic electric control device whose output provides a constant voltage supply, even though the line voltage at its input may vary.

voltage-to-ground 1. In a grounded electric circuit, the voltage between the given conductor and that point of the circuit which is grounded. 2. In an ungrounded circuit, the greatest voltage between the given conductor and any other conductor in the circuit.

voltage transformer A transformer whose primary is connected to a medium-voltage source and whose secondary is connected to a load at lower voltage.

voltmeter An instrument for measuring the voltage drop between any two points in an electric circuit.

volume batching Measuring the constituent materials for mortar or concrete by volume, rather than by weight.

volume method A method of estimating probable total construction cost by multiplying the adjusted gross building volume by a predetermined cost per unit volume.

volume strain See bulk strain.

volumeter 1. An instrument for measuring the volume of a gas or liquid. 2. A type of flushometer.

volumetric absorption The ratio of the volume of a liquid, that is absorbed by a mass to the volume of the mass.

volume yield See yield, 1.

voluntary standard A standard with which there is no obligation to comply, either legally or de facto.

volute 1. A spiral scroll, as on Ionic, Corinthian, or Composite capitals, or on consoles, etc. 2. A stair crook having an easement with a spiral section of stair rail.

vomitorium A vomitory in an ancient Roman theater or amphitheater.

vomitory An entrance or opening, usually one of a series, which pierces a bank of seats in a theater, stadium, or the like.

voussoir A wedge-shaped masonry unit in an arch or vault whose converging sides are cut as radii of one of the centers of the arch or vault.

voussoir brick Same as arch brick.

VP On drawings, abbr. for vent pipe.

V-roof A peaked roof, gable roof, or the like.

VS 1. On drawings, abbr. for “versus.” 2. Abbr. for vent stack. 3. Abbr. for “vapor seal.”

V-shaped joint, V-joint, V-tooled joint 1. A horizontal V-shaped mortar joint made with a steel jointing tool; very effective in resisting the penetration of rain. 2. A joint formed by two adjacent wood boards, in the same plane, which have faces with chamfered edges.

V-tool A gouge with a V-shaped cutting edge; see also parting tool.

V-tooled joint See V-shaped joint.

vug A pit-like natural cavity in stone, usually between a small fraction of an inch and a few inches in diameter; may be lined with crystals or layers of mineral materials; most common in dolomite, limestone, and marble.

vulcanization An irreversible process during which a rubber compound, through a change in its chemical structures, becomes less plastic, more resistant to swelling by organic liquids, and more elastic (or the elastic properties are extended over a greater range of temperature).