AGGREGATE—Crushed stone, slag or water-worn gravel that comes in a wide range of sizes. Used to surface built-up roofs.
ALLIGATORING—A characteristic of asphalt which occurs during the aging process in which the loss of volatile oils and the oxidation brought about by solar radiation produces a pattern of cracks which resemble an alligator hide, because of the limited tolerance of asphalt to thermal expansion or contraction.
ASPHALT—A dark brown to black, highly viscous, hydrocarbon produces from the residue left after the distillation of petroleum, used as a waterproofing agent.
BASE PLY—An asphalt-saturated and/or coated felt installed as the first ply with 4 inch laps in a built-up roof system under the following felts which can be installed in a shingle like fashion.
BATTEN PLAT—A formed piece of metal designed to cover the joint between two lengths of metal edge.
BITUMEN—Any of various mixtures of hydrocarbons occurring naturally or obtained through the distillation of coal or petroleum. (See Coat Tar Pitch and Asphalt)
BLISTER—An enclosed raised spot evident on the surface of a roof. They are mainly caused by the expansion of trapped air, water vapor, moisture or other gases. Blisters on a roof may involve only the coating, one or more plies of felt or may involve the whole membrane thickness.
BEAD—A semi-rounded strip (bead) of caulking material.
BEAM—A heavy main support structure, steel or wood running horizontally between columns or load bearing walls.
BOND BREAKER—A substance or a tape applied between two adjoining materials to prevent adhesion between them.
BREAK METAL—Sheet metal that has been bent to the desired configuration.
BUILT-UP ROOF (BUR)—A roof consisting minimally of a BUR membrane but may also include insulation, vapor retarders and other components.
BUILT-UP ROOF MEMBRANE (BURM)—A built-up roof consisting of plies or layers of roofing felt bonded together on site with bitumen; either tar or asphalt.
BULB-TEE—A specialized steel reinforcing member which support form boards and reinforces a gypsum deck, which when poured surrounds the Bulb-Tee.
BUTTERFLY ROOF—A roof assembly which pitches sharply from either side toward the center.
CANOPY—An overhanging roof.
CANT STRIP—A beveled support used at the intersection of the roof deck with vertical surfaces so that bends in the roofing membrane to form base flashings can be made without breaking the felts.
CAP SHEETS—One to four plies of felt bonded and top coated with bitumen that is laid over an existing roof as a treatment for defective roofs.
CEMENT, ROOFING—A general term for a variety of trowelable mastics, asphalt or tar, which are used during roof construction and repair.
CHALK (ing) —The resulting dust which occurs on a surface that is susceptible to Ultra Violet degradation.
CHECKING—A pattern of surface cracks running in irregular lines. When found in the top pour of an asphalt built-up roof, is the preliminary stage of alligatoring.
CLEAT—A device made of formed sheet metal which is mechanically attached onto which the fascia flange of a metal edge is snapped, so as to protect against wind uplift.
COAL TAR PITCH (Tar) — A bituminous material which is a byproduct from the coking of coal. It is used as the waterproofing material for tar and gravel built-up roofing.
COATING—A layer of any brush consistency product spread over a surface for protection.
COLD APPLIED—Products that can be applied without heating. These are in contrast to tar or asphalt which needs to be heated to be applied.
COLD PATCH—A roof repair done with cold applied material.
COLLAR—A conical metal cap flashing used in conjunction with vent pipes or stacks usually located several inches above the plane of the roof, for the purpose of shedding water away from the base of the vent.
COMPATIBLE—Two or more substances which can be mixed or blended without separating, reacting, or affecting either material adversely.
COMPONENT—Any one part of an assembly associated with construction.
COMPOSITE BOARD—An insulation board which has two different insulation types laminated together in 2 or 3 layers.
CONDUCTOR—A pipe for conveying rain water from the roof gutter to a drain or from a roof drain to the storm drain; also called a leader, downspout, or downpipe.
COOLING TOWER—A large device mounted on roofs, consisting of many baffles over which water is pumped in order to reduce its temperature.
CORE—A small section cut from any material to show internal composition. The core was taken from the roof to verify the construction of the existing roof system. The deck is visible along with the insulation and the roof membrane (see construction section). The core was then replaced and repaired immediately with the appropriate mastic and Fiberglas reinforcing mesh.
CORNICE—A horizontal projecting course on the exterior of a building, usually at the base of the parapet.
CORROSION—The deterioration of metal by chemical or electrochemical reaction resulting from exposure to weathering, moisture, chemicals or other agents or media.
CONTROL JOINT—A control joint controls or accommodates movement in the surface component of a roof.
COPING—A construction unit placed at the top of the parapet wall to serve as a cover for the wall.
CORRUGATED—Folded or shaped into parallel ridges or furrows so as to form a symmetrically wavy surface.
COURSE—A single layer of brick or stone or other building material.
CRAZING—A series of hairline cracks in the surface of weathered materials, having a web-like appearance.
CRICKET—The evaluation of a part of a roof surface as a means of promoting drainage of water from behind an obstacle such as chimney.
CUPOLA—A small monitor or dome at the peak of a pitched roof.
CURB—A short wall or masonry built above the level of the roof. It provides a means of flashing the deck equipment.
CUTBACK—Basic asphalt or tar which has been "cutback" with solvents and oils so that the material become fluid.
CUT OFF—A piece of roofing membrane consisting of one or more narrow plies of felt usually moped in hot to seal the edge of insulation at the end of a day's work.
DAMPPROOFING—A process used on concrete, masonry or stone surfaces for the purpose of repelling water. Moisture vapor readily penetrates coatings of this type. The main purpose of damp proofing is to prevent the coated surface from absorbing rain water while allowing is to breathe moisture vapor out of the structure.
DEAD LOAD—The constant designed weight (of the roof) and any permanent fixtures attached above or below.
DECK—The base surface to which a roof system is applied.
DEFLECT—To bend or deform underweight.
DEW POINT—The critical temperature at which vapor condenses from the atmosphere and forms water.
DORMER—The house-like structure which projects from a sloping roof.
DOUBLE TEE—Refers usually to a precast roof deck panel poured with two fins in its underside to impart flexural rigidity.
DOWNSPOUT—The metal pipe used to drain water from a roof.
DRAWING OUTLINE—A top view drawing, of a building or roof showing only the perimeter drawn to scale.
DRAWING DETAIL—A top view drawing, of a building or roof showing the roof perimeter and indicating the projections and roof mounted equipment, drawn to scale.
DRIP EDGE—A device designed to prevent water from running back or under an overhang.
DRIPPAGE—Bitumen material that drips through roof deck joints, or over the edge of a roof deck.
DRY LAP—A term describing the absence of bitumen between the plies of felt at the overlap in a BURM.
DRY SHEET—A ply mechanically attached to wood or gypsum decks to prevent asphalt or pitch from penetrating the deck and leaking into the building below.
DUCT—A cylindrical or rectangular "tube" used to move air either from exhaust or intake. The installation is referred to as "duct work".
EPDM—Ethylene Propylene Diene Monomer. A single ply membrane consisting of synthetic rubber; usually 45 or 60 mils. Application can be ballasted, fully adhered or mechanically attached.
EAVE—The part of a roof which projects out from the side wall, or the lower edge of the part of a roof that overhangs a wall.
EDGE METAL—A term relating to brake or extruded metal around the perimeter of a roof.
EFFLORESCENCE—The process by which water leeches soluble salts out of concrete or mortar and deposits them on the surface. Also used as the name for these deposits.
ELASTOMERIC—A general term, any of the numerous flexible roof membranes that contain rubber or plastic.
EMULSION—In roofing, a coating consisting of asphalt and fillers suspended in water.
END LAP—The amount or location of overlap at the end of a roll of roofing felts in the application.
E.V.T. EQUI-VISCOUS TEMPERATURE—The critical temperature at which asphalt reaches the viscosity most favorable to good adhesion when applied in a BUR.
EXPANSION COEFFICIENT—The amount that a specific material will vary in any one dimension with a change of temperature.
EXPANSION JOINT—A device used to make up the motion of expansion and contraction. On large roofs this provision for the movement of the materials forming the walls, roof deck and roof covering is usually made by deliberately separating the building into sections, and covering separation between adjacent sections with the expansion joint to allow movement but keep out the weather. Expansion joints, unlike control joints, penetrate through the roof deck.
EXTRUSION—An item formed by forcing a base metal (frequently aluminum) or plastic, at a malleable temperature, through a die to achieve a desired shape.
EYEBROW—A flat, normally concrete, projection which protrudes horizontally from a building wall; Eyebrows are generally located above windows.
FACADE—The front of a building. Frequently, in architectural terms an artificial or decorative effort.
FACTORY MUTUAL FM—A major insurance agency who has established stringent guidelines for maximum construction integrity as it relates to fire and environmental hazards. Their specifications have become industry standards.
FASCIA—Any cover board at the edge or eaves of a flat, sloping, or overhanging roof which is placed in a vertical position to protect the edge of the roof assembly.
FASTENERS—A general term covering a wide variety of screws and nails which may be used for mechanically securing various components of a building.
FELT—A very general term used to describe composition of roofing ply sheets, consisting of a mat of organic or inorganic fibers unsaturated, impregnated with asphalt or coal tar pitch, or impregnated and coated with asphalt.
FIRE WALL—Any wall built for the purpose of restricting or preventing the spread of fire in a building. Such walls of solid masonry or concrete generally sub-divided a building from the foundations to two or more feet above the plane of the roof.
FISHMOUTH—A characteristic opening at the exposed lap edge of BUR felts due to loss of bond or wrinkling of the felt.
FLAKE—A scale like particle. To lose bond from a surface in small thin pieces. Sometimes a paint film "flakes".
FLASHING—Connecting devices that seal membrane joints at expansion joints, walls, drains, gravel stops, and other places where the membrane is interrupted or terminated.
FLASHING BASE—The upturned edge of the watertight membrane formed at a roof termination point by the extension of the felts vertically over the cant strip and up the wall for a varying distance where they are secured with mechanical fasteners.
FLASHING, COUNTER—The formed metal secured to a wall, curb, or roof top unit to cover and protect the upper edge of a base flashing and its associated fasteners.
FLASH POINT—The critical temperature at which a material will ignite.
FLASHING, THRU-WALL—Flashing extended completely through a masonry wall. Designed and applied in combination with counter flashing, to prevent water which may enter the wall above from proceeding downward in the wall or into the roof deck or roofing system.
FOLDED SEAM—In sheet metal work, a joint between sheets of metal wherein the edges of the sheets are crimped together and folded flat.
FLAT SEAM—A seam at the junction of sheet metal roof components that has been bent at the plane of the roof.
FLOP—Cutting of felts into strips, coating the deck side with bitumen and placing (flopping) the felt onto the deck.
FLASHING, STEP—Individual small pieces of metal flashing material used to flash around chimneys, dormers, and such projections along the slope of a roof. The individual pieces are overlapped and stepped up the vertical surface.
FULLY ADHERED—A completely attached (adhered) roof membrane.
GABLE—The end of a building as distinguished from the front or rear side. The triangular end of and exterior wall from the level of the eaves to the ridge of a double sloped roof.
GAMBREL ROOF—A type of roof which has its slope broken by an obtuse angle, so that the lower slope is steeper than the upper slope. A double sloped roof having two pitches.
GALVANIZE—To coat a metal with zinc by dipping in molten zinc after cleaning.
GAUGE—The thickness of sheet metal and wire, etc.
GLAZE COAT—A light, uniform mopping of bitumen on exposed felts to protect them from the weather, pending completion of the job.
GRANULES—The mineral particles of a graded size which are embedded in the asphalt coating of shingles and roofing.
GRAVEL—Loose fragments of rock used for surfacing built-up roofs, in sizes varying from 1/8" to 1 3/4".
GROUT OR GROUTING—A cement mortar mixture commonly used to fill joints and cavities of masonry. On roof decks, the joints between many types of precast roof deck slabs are grouted with cement grout.
GUTTER—Metal trough at the eaves of a roof to carry rain water from the roof to the downspout.
GUTTER STRAP—Metal bands used to support the gutter.
GUY WIRE—A strong steel wire or cable strung from an anchor on the roof to any tall slender projection for the purpose of support.
GYPSUM—A hydrated sulfate of calcium occurring naturally in sedimentary rock. In roofing, a type of lightweight deck made from this pulverized rock.
HATCH—An opening in a deck; floor or roof. The usual purpose is to provide access from inside the building.
HIP ROOF—A roof which rises by inclining planes from all four sides of a building.
INCOMPATIBILITY—Descriptive of two or more materials which are not suitable to be used together.
INSIDE DRAIN—A roof drain positioned on a roof at some location other than the perimeter. It drains surface water inside the building through closed pipes to a drainage system.
INSULATION—Material which slows down or retards the flow or transfer of heat.
INSULATION FASTENERS—Any of several specialized mechanical fasteners designed to hold insulation down to steel or a nailable deck.
INSULATION VENT—A vent placed into the insulation which extends above the BURM.
INTERPLY IRMA—Insulated (or Inverted) Roof Membrane Assembly. In this system the roof membrane is laid directly on the roof deck, covered with extruded foam insulation and ballasted with stone, minimum of 1000 lbs. per square.
JOIST—A horizontally placed timber or beam set on edge to give support to a floor or ceiling.
KETTLE—Equipment used for heating bitumen to a flowing consistency.
KICK HOLE—A defect frequently found in perimeter flashings arising from being stepped on or kicked. A small fracture of the base flashing in the area of the cant.
KRAFT—A heavy water resistant paper.
LADDER, FIXED—A ladder which is permanently attached to a building.
LAP—To extend one material partially over another; the distance so extended.
LEAD—A malleable metal once extensively used for flashings.
LEAN-TO-ROOF—The sloping roof of a building addition having its rafters or supports pitched against and supported by the adjoining wall of a building.
LIQUID-APPLIED MEMBRANE—Generally applied to cast-in-place concrete surfaces in one or more coats to provide fully-adhered waterproof membranes which conform to all contours.
MANSARD ROOF—A roof which rises by inclined planes from all four sides of a building. The sloping roofs on all four sides have two pitches, the lower pitch usually very steep and the upper pitch less steep.
MASTIC—A heavy trowel applied bitumen used for flashings or patch work which remains elastic and pliable.
MELT POINT—The temperature at which the solid asphalt becomes a liquid.
MEMBRANE—A generic term relating to a variety of sheet goods used for certain built-up roofing repairs and application. Also used to describe the combination of felts and mopping of bitumen forming a single flexible unit and waterproofing system of a BUR.
LIVE LOAD—The weight superimposed by snow or water or other tangibles which lack permanency, not including the wind load, on a roof.
LOOSE LAID—A membrane "laid loosely", i.e., not adhered, over a roof deck or BURM.
METAL EDGE—Brake metal or metal extrusions which are secured at the perimeter of BURM to form a weathertight seal.
MIL THICKNESS—Measurement used to determine thickness of a coating. 1 mil = .001 inch (1/1000).
MINERAL SPIRITS—A by-product of petroleum, clear in color, a solvent for asphaltic coatings.
MINERAL SURFACED—heavy roofing felt that has very small granules embedded across its surface.
MODIFIED BITUMEN—Bitumen modified by special processing, generally with the addition of SBS type rubber or atactic polypylenes (APP). Some are non-reinforced, while others are reinforced with polyester, polyvinyl acetate, fiberglass, polypropylene or aluminum foil.
MONITOR, SAW-TOOTH—A type of monitor characterized by sharp angled pitches and vertical sections, usually arranged in rows much like teeth of a saw.
MONITOR—A large structure rising above the surrounding roof planes, designed to give light and/or ventilation to the building interior.
MOPPING—A layer of hot bitumen mopped between plies of roofing felt.
MOPPING, FULL—The application of bitumen by mopping in such a manner that the surface being mopped is entirely coated with a reasonably uniform coating.
MOPPING, SPOT—The procedure of applying hot bitumen in a random fashion of small daubs, as compared to full mopping.
MOPPING, SPRINKLE—A special application of installing insulation to the decks. It is done by dipping a roof mop into hot bitumen and sprinkling the material onto the deck.
MOPPING, STRIP—The application of bitumen in parallel bands.
MUD CRACKS—Cracks developing from the normal shrinkage of an emulsion coating when applied too heavily.
NAILER—A piece of lumber secured to non-nailable decks and walls by bolts or other means, which provides a suitable backing onto which roof components may be mechanically fastened.
NON-DESTRUCTIVE—A phrase describing a method of examining the interior of a component whereby no damage is done to the component itself.
NUCLEAR METER—A device used to detect moisture by measuring slowed, deflected neutrons.
OIL-CANNING—The term describing distortion of thin-gauge metal panels which are fastened in a manner restricting normal thermal movement.
ORGANIC—A term designating any chemical compound which contains carbon and hydrogen.
OVERHANG—That part of the roof structure which extends horizontally beyond the vertical plane of the exterior walls of a building.
OXIDIZE—To combine with oxygen in the air.
PARAPET WALL—A low wall around the perimeter of a roof deck.
PARGE COAT—A thin application of plaster for coating a wall.
PAVER STONES—Usually pre-cast concrete slabs used to create a traffic surface.
PENTHOUSE—A relatively small structure built above the plane of the roof.
PERLITE—An aggregate formed by heating and expanding siliceous volcanic glass.
PHASE CONSTRUCTION—In roofing the practice of applying the felt plies of the built-up roofing membrane in two or more operations, separated by a delay of at least one day.
PHOTO-OXIDATION—Oxidation caused by rays of the sun.
PITCH—A term frequently used to designate coal tar pitch.
PITCH PAN OR POCKET—A bottomless metal box placed on the BURM around irregular projections. These are subsequently filled with coal tar pitch or mastic to affect a weather tight seal.
PLY—A single course of roofing felts.
PLYWOOD—Wooden panels formed by gluing thin sheets of wood together, with the grain of adjacent layers arranged at right angles.
POINTING—The process where joints between masonry units, brick, etc., are filled with mortar.
POLYMER—A substance consisting of large molecules which have been formed from smaller molecules of similar make-up.
POLYURETHANE—Any of various polymers with a urethane base.
PONDING—A condition where water stands on a roof for prolonged periods due to poor drainage and/or deflection of the deck.
POP RIVETS—Fasteners used to join pieces of metal that are installed by either compressed air assisted or hand operated guns. Unique in that they are installed from one side of the work.
POROSITY—The density of substance and its capacity to pass liquids.
POUR COAT—The top coating of bitumen on a built-up roof.
PRECAST—Concrete building components which are formed and cured at a factory and then transported to a work site for erection.
PRIMER—A material of relatively thin consistency applied to a surface for the purpose of creating a more secure bonding surface.
PROJECTION—Any object or equipment which pierces the roof membrane.
PROTECTION BOARD—Heavy asphalt impregnated boards which are laid over bituminous coatings to protect against mechanical injury.
PURLINS—A horizontal structural member spanning between beams or trusses to support a roof deck.
RAGGLE BLOCK—A specially designed masonry block having a slot or opening into which the top edge of the roof flashing is inserted and anchored.
RAKE—The angle of slope of a roof rafter, or the inclined portion of a cornice.
REFLECTIVE—A term referring to a material that has a white or shiny metallic surface.
REGLET—A horizontal slot, formed or cut in a parapet or other masonry wall, into which the top edge of counterflashing can be inserted and anchored.
RE-IMPREGNATE—To replace oils and bitumen in the components of the BURM which through weathering and oxidation, have been lost.
ROOF—The assembly of interacting components designed to weatherproof and normally to insulate a buildings surface, separated from adjacent assemblies by walls or changes in elevation.
ROOF COATING—A bituminous material, either a cutback or an emulsion, to protect the surface of the BURM but not necessarily to re-impregnate it.
ROOF DECK—That component in building construction, which forms a platform on which the remainder of the BURM components is placed.
ROOF DRAIN—The termination or fitting at the roof of an interior drain or leader, for draining rain water from nominally flat roofs.
ROOF SYSTEM—General term referring to the waterproof covering, roof insulation, vapor barrier, if used and roof deck as an entity.
RUN—The horizontal distance between the eaves and the ridge of the roof, being half the span for a symmetrical gable roof.
SADDLE—A ridge in the roof deck, whose top divides two sloping parts of the roof so that water will be diverted to the roof, drains.
SAW TOOTH ROOF—Where reviewed from the end, such a roof serrated or tooth profile similar to the teeth of a saw.
SCRIM—A woven or mat-type fabric that is used as a membrane sandwich between other material to provide reinforcement and stretch resistance.
SCUPPER—An outlet in the wall of a building or a parapet wall for drainage of water from a flat roof.
SELF-HEALING—A term used in reference to a material which melts with the heat from the sun's rays, and seals over cracks that were earlier formed from other causes.
SELF-LEVELING—A viscous material that is applied by pouring. In its uncured state, it spreads out evenly.
SELVAGE—The unsurfaced strip along a sheet of roll roofing which forms the under portion at the lap in the application of the roof covering.
SHED ROOF—A roof having only one slope or pitch, with only one set of rafters which fall from a higher to a lower wall.
SHEATHING—The boards of sheet type material, plywood or asphalt saturated sheets, nailed to studding or roofing rafters as the base for application of the roof covering.
SHINGLE-FASHION—The pattern formed by laying parallel felt rolls with lapped joints so that one longitudinal edge overlaps the longitudinal edge on the adjacent felts. Shingle fashion applications begin at the low point on a roof so that one ply drains water to a lower one and so on to a drain or to the roof edge.
SHINGLES—Small units of material which are laid in a series of overlapping rows as a roof covering on pitched roofs.
SIGN ANCHOR—A component usually formed with steel angles which penetrates the BUR and is fastened to the deck.
SINGLE PLY—A descriptive term signifying a roof membrane composed of only one layer of material such as EPDM, TPO or PVC.
SINGLE TEE—The name given to a type of precast concrete deck which has one stiffening rib integrally cast into slab.
SITE—The physical grouping of a number of roofs or buildings at a geographical location.
SKY DOME—A type of skylight exhibiting a characteristic translucent plastic domed top.
SKYLIGHT—A structure on a roof that is designed to admit light and is somewhat above the plane of the roof surface.
SLAG—A by-product of smelting ore such as iron, lead or copper.
SLATE—A dark gray stratified stone cut relatively thin and installed on pitched roofs in a shingle like fashion.
SLIPPAGE—It is the sliding, lateral movement between adjacent to plies of felt along the plane of the bitumen film separating them, which results in a randomly wrinkled appearance.
SLOPE—Incline or pitch of roof surface.
SOFFIT—The underside of a part or member of a building extending out from the plane of the building walls.
SOFTENING POINT—The temperature at which a substance changes from a hard material to a softer and more viscous material.
SPALLING—The chipping or flaking of concrete, bricks, or other masonry where improper drainage or venting and freeze/thaw cycling exists.
SPAN—The horizontal distance between supporting structures such as beams, trusses or columns.
SPECIFICATION—Detailed written instructions which, when clear and concise, explain each phase of work to be done.
SPLITTING—The formation of long cracks completely through a roof membrane. Splits are frequently associated with lack of allowance for expansion stresses. They can also be a result of deck deflection or change in deck direction.
SQUARE—A term used by the roof industry to indicate an amount of roof area equal to 100 square feet.
SPUD—The removal of gravel or heavy accumulations of bitumen from roof membranes by means of chipping or scraping
STACK—A vertical pipe projecting through a BUR that carries off smoke or gases.
STANDING SEAM—A type of joint often used on metal roofs.
STARTER STRIPS—In the construction of the BUR the narrow strips of roofing felts, cut from standard width rolls, that are applied at the beginning point so as to assure uniform configuration of the specified number of plies.
STATIC LOAD—In roofing the total amount of permanent nonmoving weight that is applied to given surface areas.
SUBSTRATE—A part or substance which lies below and supports another.
SUMP—A reservoir sometimes forming part of a roof drain. A depression in the roof deck of a building at a roof and delivery it to the drain.
TEAR OFF—A term used to describe the complete removal of the built up roof membrane and insulation down to and exposing the roof deck.
THERMAL MOVEMENT—The measured amount of dimensional change, a material exhibits as it is warmed or cooled.
THERMAL SHOCK—The stress built up by sudden and appreciable changes in temperature.
THERMOPLASTIC MATERIAL—Solid material which is softened by increasing temperatures and hardened by decreasing temperatures.
TIE-IN—A term used to describe the joining of a new roof with the old.
Cast concrete units which are preformed which, when cured, are tilted to their vertical position and secured by mechanical fasteners to prior erected structural steel. May be pre-cast.
TOP MOPPING—The finished mopping of hot bitumen on a built-up roof.
TORCHING—Applying direct flame to a membrane for the purpose of melting, heating or adhering.
TRUSS—A major supporting structure usually timber for roof decks.
TUCK POINTING—The re-grouting of defective mortar joints in a masonry or brick wall.
ULTRAVIOLET—The invisible rays of the spectrum which are at its violet end. Sometimes abbreviated U.V.
VALLEY—A term applied to a depressed angle formed by the meeting of two inclined slopes of a roof.
VAPOR—The gaseous form of any substance.
VAPOR RETARDER (BARRIER) —A membrane which is placed between the insulation and the roof deck to retard water vapor in the building from entering the insulation and condensing into liquid water.
VEINING—The characteristic lines or "stretch marks" which develop during the aging process of soft bitumen.
VENT PIPE—A vertical pipe of relatively small dimensions which protrudes through a roof to provide for the ventilation of gasses.
VENTILATOR—Device installed on the roof for the purpose of ventilating the interior of the building.
VENTING—1. The process of installing roof vents in a roof assembly to relieve vapor pressure. 2. 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.
VERTICAL APPLICATION—Roll roofing laid parallel to the slope of a roof.
VISCOSITY—The internal frictional resistance offered by a fluid to change of shape or to the relative motion or flow of its parts.
WALKWAYS—Designated areas for foot traffic on roofs.
WATER STOP—A device designed to protect the exposed edge of a partially installed BURM from water entrance.
WATERPROOFING—The process where a building component is made totally resistant to the passage of water and/or water vapor.
WATER VAPOR—Moisture existing as a gas in air.
WEEP HOLE—A hole which allows for drainage of entrapped water from masonry structures.
WELD—The joining of components together by fusing. In thermoplastics, refers to bonding together of the membrane using heat or solvents.
WIND UPLIFT—The upward force exerted by wind traveling across a roof.
WRINKLE—A raised pattern of ridges running in a random fashion in a BUR.
ZONOLITE—A lightweight, insulating concrete composed of Portland cement, water, and vermiculite aggregate.