Glossary of Terms
Adhere
To cause two surfaces to be held together by adhesion, typically with asphalt or roofing cements in built-up roofing and with contact cements in some single-ply membranes
Aggregate
Rock, stone, crushed stone, crushed slag, water worn gravel or marble chips used for surfacing and/or ballasting a roof system.
Aging
The effect on materials that are exposed to an environment for an interval of time.
Alligatoring
The cracking of the surfacing bitumen on a built-up roof, producing a pattern of cracks similar to an alligator's hide; the cracks may or may not extend through the surfacing bitumen.
Application Rate
The quantity (mass, volume, or thickness) of material applied per unit area.
Area Divider
A raised, flashed assembly (typically a single- or double-wood member attached to a wood base plate) that is anchored to the roof deck. It is used to relieve thermal stresses in a roof system where an expansion joint is not required, or to separate large roof areas (sometimes between expansion joints), and may be used to facilitate installation of tapered insulation.
Asbestos
A group of natural, fibrous, impure silicate materials used to reinforce some roofing products.
Asphalt
A dark brown or black substance found in a natural state or, more commonly, left as a residue after evaporating or otherwise processing crude oil or petroleum. Asphalt may be further refined to conform to various roofing grade specifications: Dead-Level Asphalt: a roofing asphalt conforming to the requirements of ASTM Specification D 312, Type I. Flat Asphalt: a roofing asphalt conforming to the requirements of ASTM Specification D 312, Type II. Steep Asphalt: a roofing asphalt conforming to the requirements of ASTM Specification D 312, Type III. Special Steep Asphalt: a roofing asphalt conforming to the requirements of ASTM Specification D 312, Type IV.
Asphalt Emulsion
A mixture of asphalt particles and an emulsifying agent such as bentonite clay and water. These components are combined by using a chemical or a clay emulsifying agent and mixing or blending machinery.
Asphalt Felt
An asphalt-saturated and/or an asphalt-coated felt. (See Felt.)
Asphaltene
A high molecular weight hydrocarbon fraction precipitated from asphalt by a designated solvent (paraffinic naphtha) at a specified temperature and solvent-asphalt ratio.
ASTM
American Society for Testing and Materials
Back-Nailing
Also referred to as Blind-Nailing, the practice of nailing the back portion of a roofing ply, steep roofing unit, or other components in a manner so that the fasteners are covered by the next sequential ply, or course, and are not exposed to the weather in the finished roof system.
Back-Surfacing
Fine mineral matter applied to the back side of asphalt shingles and roll roofing to keep them from sticking together while packaged.
Ballast
An anchoring material, such as aggregate, or precast concrete pavers, which employ the force of gravity to hold (or assist in holding) single-ply roof membranes in place.
Base Flashing
Plies or strips of roof membrane material used to close-off and/or seal a roof at the roof-to-vertical intersections, such as at a roof-to-wall juncture. Membrane base flashing covers the edge of the field membrane. (Also see Flashing.)
Base Ply
The lowermost ply of roofing in a roof membrane or roof system.
Base Sheet
An impregnated, saturated, or coated felt placed as the first ply in some multi-ply built-up and modified bitumen roof membranes.
Batten
(1) cap or cover; (2) in a metal roof: a metal closure set over, or covering the joint between, adjacent metal panels; (3) wood: a strip of wood usually set in or over the structural deck, used to elevate and/or attach a primary roof covering such as tile; (4) in a membrane roof system: a narrow plastic, wood, or metal bar which is used to fasten or hold the roof membrane and/or base flashing in place.
Bird Screen
Wire mesh used to prevent birds from entering the building through ventilators, louvers, or other openings.
Bitumen
(1) A class of amorphous, black or dark colored, (solid, semi-solid, or viscous) cementitious substances, natural or manufactured, composed principally of high molecular weight hydrocarbons, soluble in carbon disulfide, and found in petroleum asphalts, coal tars and pitches, wood tars and asphalts; (2) a generic term used to denote any material composed principally of bitumen, typically asphalt or coal tar.
Bituminous Emulsion
A suspension of minute particles of bituminous material in water or other aqueous solution. (See Asphalt Emulsion.)
Blanket (Batt) Insulation
Fiberglass or other compressible fibrous insulation, generally available in roll form.
Bleed-Sheet
A sheet material used to prevent the migration of bitumen.
Blind-Nailing
The use of nails that are not exposed to the weather in the finished roofing system.
Blister
An enclosed pocket of air, which may be mixed with water or solvent vapor, trapped between impermeable layers of felt or membrane, or between the membrane and substrate.
Blocking
Sections of wood (which may be preservative treated) built into a roof assembly, usually attached above the deck and below the membrane or flashing, used to stiffen the deck around an opening, act as a stop for insulation, support a curb, or to serve as a nailer for attachment of the membrane and/or flashing.
Blowing Agent
An expanding agent used to produce a gas by chemical or thermal action, or both, in manufacture of hollow or cellular materials.
Bond
The adhesive and/or cohesive forces holding two components in positive contact.
Bond, Chemical
Adhesion between surfaces, usually of similar materials, resulting from a chemical reaction or cross-linking of polymer chains.
Bonding Agent
A chemical substance applied to a suitable substrate to create bond between it and a succeeding layer.
Boot
(1) a covering made of flexible material, which may be preformed to a particular shape, used to exclude dust, dirt, moisture, etc. from around a penetration; (2) a flexible material used to form a closure, sometimes installed at inside and outside corners.
Bridging
(1) when the membrane is unsupported at a juncture; (2) bridging in steep-slope roofing is a method of reroofing over standard-sized asphalt shingles with metric-sized asphalt shingles.
British Thermal Unit (BTU)
The heat energy required to raise the temperature of one pound of water one degree Fahrenheit (joule).
Brooming
An action carried out to facilitate embedment of a ply of roofing material into hot bitumen by using a broom, squeegee, or special implement to smooth out the ply and ensure contact with the bitumen or adhesive under the ply.
Buckle
An upward, elongated tenting displacement of a roof membrane frequently occurring over insulation or deck joints. A buckle may be an indication of movement within the roof assembly.
Building Code
Published regulations and ordinances established by a recognized agency prescribing design loads, procedures, and construction details for structures. Usually applying to designated jurisdictions (city, county, state, etc.). Building codes control design, construction, and quality of materials, use and occupancy, location and maintenance of buildings and structures within the area for which the code has been adopted.
Built-Up Roof Membrane (BUR)
A continuous, semi-flexible multi-ply roof membrane, consisting of plies or layers of saturated felts, coated felts, fabrics, or mats between which alternate layers of bitumen are applied. Generally, built-up roof membranes are surfaced with mineral aggregate and bitumen, a liquid-applied coating, or a granule-surfaced cap sheet.
Butt Joint
A joint formed by adjacent, separate sections of material, such as where two neighboring pieces of insulation abut.
Butyl
Rubber-like material produced by copolymerizing isobutylene with a small amount of isoprene. Butyl may be manufactured in sheets, or blended with other elastomeric materials to make sealants and adhesives.
Butyl Coating
An elastomeric coating system derived from polymerized isobutylene. Butyl coatings are characterized by low water vapor permeability.
Butyl Rubber
A synthetic elastomer based on isobutylene and a minor amount of isoprene. It is vulcanizable and features low permeability to gases and water vapor.
Butyl Tape
A sealant tape sometimes used between metal roof panel seams and end laps; also used to seal other types of sheet metal joints, and in various sealant applications.
Canopy
Any overhanging or projecting roof structure, typically over entrances or doors. Sometimes the extreme end is unsupported.
Cant Strip
A beveled or triangular-shaped strip of wood, wood fiber, perlite, or other material designed to serve as a gradual transitional plane between the horizontal surface of a roof deck or rigid insulation and a vertical surface.
Cap Flashing
Usually composed of metal, used to cover or shield the upper edges of the membrane base flashing, wall flashing, or primary flashing. (See Flashing and Coping.)
Cap Sheet
A granule-surface coated sheet used as the top ply of some built-up or modified bitumen roof membranes and/or flashing.
Capillary Action
The action that causes movement of liquids by surface tension when in contact with two adjacent surfaces such as panel side laps.
Catalyst
An ingredient in a coating of SPF which initiates a chemical reaction or increases the rate of a chemical reaction.
Caulk
A material (usually a composition of vehicle and pigment) used for filling/sealing joints or junctures, where no elastomeric properties are required. (See Sealant.)
Caulking
(1) the physical process of sealing a joint or juncture; (2) sealing and making weather-tight the joints, seams, or voids between adjacent units by filling with a sealant.
Cavity Wall
A wall built or arranged to provide an air space within the wall (with or without insulating material), in which the inner and outer materials are tied together by structural framing.
Chalking
The degradation or migration of an ingredient, in paints, coatings, or other materials.
Cladding
A material used as the exterior wall enclosure of a building.
Cleat
A metal strip, plate or metal angle piece, either continuous or individual (clip), used to secure two or more components together.
Clip
An individual (discrete) cleat. (See Cleat.)
Closure Strip
A metal or resilient strip, such as neoprene foam, used to close openings created by joining metal panels or sheets and flashings
Coal Tar
A dark brown to black colored, semi-solid hydrocarbon obtained as residue from the partial evaporation or distillation of coal tars. Coal tar pitch is further refined to conform to the following roofing grade specifications.
Coal Tar Bitumen
A proprietary trade name for Type III coal tar used as the damp proofing or waterproofing agent in dead-level or low-slope built-up roof membranes, conforming to ASTM D 450, Type III.
Coal Tar Felt
A felt that has been saturated with refined coal tar.
Coal Tar Pitch
A coal tar used as the waterproofing agent in dead-level or low-slope built-up roof membranes, conforming to ASTM Specification D 450, Type I or Type III.
Coal Tar Roof Cement
A trowelable mixture of processed coal tar base, solvents, mineral fillers and/or fibers. Classified by ASTM Standard D 4022 Coal Tar Roof Cement.
Coated Base Sheet
A felt that has previously been saturated (filled or impregnated) with asphalt and later coated with harder, more viscous asphalt, which greatly increases its impermeability to moisture.
Coated Fabric
Fabrics that have been impregnated and/or coated with a plastic-like material in the form of a solution, dispersion hot-melt, or powder. The term also applies to materials resulting from the application of a preformed film to a fabric by means of calendering.
Cold Process Built-Up Roof
A continuous, semi-flexible roof membrane, consisting of a ply or plies of felts, mats or other reinforcement fabrics that are laminated together with alternate layers of liquid-applied (usually asphalt-solvent based) roof cements or adhesives installed at ambient or a slightly elevated temperature.
Combustible
Capable of burning.
Compatible Materials
Two or more substances that can be mixed, blended, or attached without separating, reacting, or affecting the materials adversely.
Composition Shingle
A unit of asphalt shingle roofing.
Compounded Thermoplastics
A category of roofing membranes made by blending thermoplastic resins with plasticizers, various modifiers, stabilizers, flame retardants, UV absorbers, fungicides, and other proprietary substances, alloyed with proprietary organic polymers. Some of the membranes listed in this generic category are CPA, EIP, NBP, and TPA.
Compressive Strength
The ability of materials and components to resist deformation or other damage caused by the weight of compression of either live or dead loads.
Condensate
The liquid resulting from the condensation of a gas or vapor.
Condensation
The conversion of water vapor or other gas to liquid state as the temperature drops or atmospheric pressure rises.
Conditioning
The exposure of a material to the influence of a prescribed atmosphere for a stipulated period of time or until a stipulated relation is reached between material and atmosphere.
Conductor Head
A transition component between a through-wall scupper and downspout to collect and direct run-off water.
Construction Joint
A formed or assembled joint at a predetermined location where two successive placements of concrete meet.
Contact Cements
Adhesives used to adhere or bond various roofing components. These adhesives adhere mated components immediately on contact of surfaces to which the adhesive has been applied.
Contamination
The process of making a material or surface unclean or unsuited for its intended purpose, usually by the addition or attachment of undesirable foreign substances.
Coping
The covering piece on top of a wall which is exposed to the weather, usually made of metal, masonry, or stone. It is preferably sloped to shed water back onto the roof.
Counterflashing
Formed metal sheeting secured on or into a wall, curb, pipe, rooftop unit, or other surface, to cover and protect the upper edge of the membrane base flashing or underlying metal flashing and associated fasteners from exposure to the weather.
Course
(1) the term used for each row of shingles of roofing material that forms the roofing, waterproofing, or flashing system; (2) one layer of a series of materials applied to a surface (e.g., a five-course wall flashing is composed of three applications of roof cement with one ply of felt or fabric sandwiched between each layer of roof cement.)
Coverage
The surface area covered by a specific quantity of a particular material.
Crack
A non-linear separation or fracture occurring in a material. May be generally caused by induced stress, dimensional instability, or substrate movement. Some cracks may be more of a linear separation or fracture.
Cricket
An elevated roof substrate or structure, constructed to divert water around a chimney, curb, away from a wall, expansion joint, or other projection/penetration.
Cupola
A relatively small roofed structure, generally set on the ridge or peak of a main roof area.
Curb
(1) A raised member used to support roof penetrations, such as skylights, mechanical equipment, hatches, etc. above the level of the roof surface; (2) a raised roof perimeter relatively low in height.
Cure
A process whereby a material is caused to form permanent molecular linkages by exposure to chemicals, heat, pressure, and/or weathering.
Downspout
A device for conveying water from a gutter or scupper to the ground.
Drip edge
A strip along the edge of the roof to control dripping which allows water to drip off the roof without affecting underlying construction.
Eaves
The horizontal lower edge of a sloped roof.
Elastomeric
Having elastic, rubberlike properties of a material.
Emulsion
A mixture of bitumen and water, with uniform dispersion of the bitumen globules achieved through a chemical or clay emulsifying agent.
EPDM
Ethylene Propylene Diene Monomer. A synthetic rubber; thermoset.
Expansion Joint
A provision in design intended to allow movement to occur within a structure at a predetermined location.
Fabric Reinforcement
A fabric, scrim, etc., used to add structural length to a two-or more ply polymeric sheet. Such sheeting is referred to as "supported."
Factory Mutual (FM)
An organization which classifies roof assemblies for their fire characteristics and wind-uplift resistance for insurance companies in the United States.
Fascia
That portion of a metal gravel stop which extends over and down the outside of eaves or edge of a roof.
Felt
A fabric manufactured by the interlocking of fibers through a combination of mechanical work, moisture, and heat without spinning, weaving or knitting. Roofing felts are manufactured from vegetable fibers, asbestos fibers or glass fibers.
Fishmouth
An opening formed by an edge wrinkle in a felt where it overlaps another felt in a built-up roofing membrane.
Flashing
The system used to seal the edges of a membrane at walls, expansion joints, drains, gravel stops, and other areas where the membrane is interrupted or terminated. Base flashing covers the edges of the membrane. Cap flashing or counter-flashing shields the upper edges of the base flashing.
Flashing Cement
A trowelable mixture of cutback bitumen and mineral stabilizers, including asbestos or other inorganic fibers.
Flat Roof
A roof with 1/8 inch or less structural slope except from deflection.
Fleece
Term used to describe mats of felts of usually non-woven fibers
Flood Coat
The top layer of bitumen in an aggregate surface, built-up roofing membrane. Correctly applied, it is poured, not mopped, to a weight of 60 pounds per square for asphalt, 75 pounds per square for coal-tar pitch.
Gable
The upper portion of a sidewall that comes to a triangular point at the ridge of a sloping roof.
Galvalume
Trade name for steel coated with aluminum-zinc for corrosion protection.
Galvanic Action
When iron and steel are subject to conditions of aqueous corrosion, the incidence and rate at which the corrosion takes place will alter if the steel is coupled with other metals or alloys that are also exposed to the electrolyte. Copper, brass, bronze, lead and nickel are more "noble" and act to accelerate its corrosion. Magnesium, zinc and zinc-base alloy are nearly always less noble and tend to divert the attack from the steel to themselves. The galvanic relationship of various metals is an important factor affecting corrosion.
Glass Fiber Felt
A felt sheet in which glass fibers are bonded into the felt sheet with resin. They are suitable for impregnation and coating. They are used in the manufacture and coating of bituminous waterproofing materials, roof membranes, and shingles.
Gravel
Coarse, granular aggregate, with pieces larger than sand grains, resulting from the natural erosion or crushing of rock.
Gravel Stop
Flanged device, normally metallic, designed to prevent loose aggregate from washing off the roof and to provide a finished edge detail for the built-up roofing assembly.
Gutter
The trough that channels water from the eaves to the downspouts.
Heat Transfer
The transmission of thermal energy from a location of higher temperature to a location of lower temperature. This can occur by conduction, convection, or radiation.
Heat Welding
The process of joining two or more thermoplastic films or sheets by heating areas in contact with each other to the temperature at which fusion occurs. The process is usually aided by a controlled pressure. In dielectric seaming, the heat is induced within films by means of radio frequency waves.
Hip
The inclined external angle formed by the intersection of two sloping roof planes.
Ice Dam
A condition formed at the lower roof edge caused by the thawing and refreezing of melted snow on the overhang. It can force water up under the shingles causing leaks.
Insulation
A material applied to reduce the flow of heat.
Lap
That part of a roofing unit that covers the preceding course in any overlapping roofing application. Applied to shingles, built-up roofing felts, and most other types of roofing.
Membrane
A flexible or semi-flexible roof covering or waterproofing layer, whose primary function is the exclusion of water.
Metal Flashing
See Flashing; metal flashing is frequently used as through-wall flashing, cap flashing, counter-flashing or gravel stops.
Mineral-Surfaced Roofing
Built-up roofing materials whose top ply consists of a granule-surface sheet.
Moisture Conduction
Migration by wicking as contrasted to vapor movement.
Mopping
An application of hot bitumen applied to the substrate or to the felts of a built-up roof membrane with a mop or a mechanical applicator.
Nailer
Wood member bolted or otherwise anchored to a non-nailable deck or wall to provide nailing anchorage of membrane, roof felts, or flashing.
NRCA
National Roofing Contractors Association.
Nuclear Roof Moisture Gauge
A nondestructive surface moisture gauge optimized for the purpose of detecting the presence of moisture in roof systems. The device uses the principle of neutron moderation.
Open Valley
A method of valley construction in which the shingles on both sides are trimmed along each side of the valley exposing the flashing.
Overlay
The practice of applying new roofing over existing roofing materials. See Recover.
Parapet Wall
That part of any wall entirely above the roof.
Patina
A green coating that forms on copper or brass or bronze that has been exposed to the air or water for long periods of time
Penetration
The consistency of a bituminous material expressed as the distance in tenths of a millimeter (.lmm) that a standard needle penetrates vertically a sample of material under specified conditions of loading, time, and temperature.
Penthouse
A room built on the a building to cover a stairway, to elevator machinery, water ventilating apparatus, or to working space above the sheaves.
Perlite
An aggregate used in lightweight insulating concrete and in preformed perlitic insulation boards, formed by heating and expanding siliceous volcanic glass.
Pipe Boot
Prefabricated flashing used to flash around circular pipe penetrations.
Pitch Pocket
A flanged, open-bottomed, metal container placed around columns or other roof penetrations that is filled with hot bitumen and/or flashing cement to seal the joint.
Pond
A roof surface which is not completely drained.
Preventative Maintenance
The regular, scheduled inspection for the repair of normal, expected failures of plant facilities.
PVC
Polyvinyl chloride single-ply membrane (as applied to roofing).
Rake
The sloped edge of a roof at the first or last rafter.
RCI
Roof Consultants Institute - An organization of members from all segments of the roofing industry devoted to the advancement of knowledge, experience and outlook.
Recover
To leave the basic existing roof system in place and to add to it additional components which may include a new overlaying membrane and, if specified, additional insulation and surfacing for their membrane.
Reglet
A groove in a wall or other vertical surface adjoining a roof surface for the embedment of counter-flashing. Sometimes called a "raggle."
Reinforced Membrane
A roofing or waterproofing membrane reinforced with felts, mats, fabrics, or chapped fiber.
Reroofing
To remove all components of the existing roofing system to the top of the decking or vapor retarder (if one is present) including the surfacing, membrane, insulation, and if specified, the vapor retarder, and to replace with new materials of like kind and approximate quantities.
Ridge
The uppermost, horizontal external angle formed by the intersection of two sloping roof planes.
Roof Consultant
An individual of established competence having professional qualifications and experience who is engaged in the field of roofing technology.
Roof System
A system of interacting roof components designed to weatherproof and normally, to insulate a building's top surface.
Rubber
A material that is capable of recovering from large deformations quickly and forcibly, and can be, or already is, modified to a state in which it is essentially insoluble(but can swell) in boiling solvent such as benzene, methyl-ethyl ketone, and ethanoltoluene azeotrope.
SBS
Styrene butadiene styrene. Used in modified bitumens as rubber additive. Considered a thermoplastic rubber exhibiting elasticity without vulcanization.
Scrim
A woven, open-mesh reinforcing fabric made from continuous filament yarn. Used in the reinforcement of polymeric sheeting.
Scupper
A parapet or other opening that allows for drainage of rain water.
Scuttle
An opening or hatchway through roof deck to permit access to roof.
Sealant
A mixture of polymers, fillers, and pigments used to fill and seal joints where moderate movement is expected; it cures to a resilient solid.
Shingle
(1) A small unit of prepared roofing material designed to be installed with similar units in overlapping rows on inclines normally exceeding 25 percent; (2) To cover with shingles; (3) To apply any sheet material in overlapping rows like shingles.
Single-Ply
A one-ply, factory-made roofing membrane.
Spud
To remove embedded aggregate from a built-up membrane surface.
Termination
The treatment or method of anchoring the free edges of the membrane in a roofing system (see Flashing).
Through-Wall Flashing
A water resistant membrane or material assembly extending through a wall and its cavities, positioned to direct any water entering the top of the wall to the exterior.
Tuckpointing
The process of removing deteriorated mortar from an existing masonry joint and troweling new mortar or other filler into the joint.
Vapor Barrier
(More precisely, vapor retarder) - A layer of material used to appreciable reduce the flow of water vapor into thermal insulation from the high vapor pressure side.
Vent
An opening designed to convey water vapor or other gas from inside a building or a building component to the atmosphere, thereby relieving vapor pressure.
Wicking
The process of moisture movement by capillary action as contrasted to movement of water vapor.
