Glossary: Common Roofing Terms
Acrylic Coating: A type of coating that has an acrylic resin base.
Aggregate: A surfacing or ballast for a roof system. Aggregate can be rock, stone, crushed stone or slag, water-worn gravel, crushed lava rock or marble chips.
Air Blown Asphalt: Asphalt produced by blowing air through molten asphalt held at an elevated temperature. This procedure is used to modify properties of the asphalt.
Alligatoring: The cracking of the surfacing bitumen on a built-up roof, producing a pattern of cracks that resemble an alligator’s hide.
APP: See Atactic Polypropylene.
Application Rate: The rate at which a material is applied per unit of area, such as gallons per square.
Architectural Shingle: A type of asphalt shingle whose raised profile mimics the random shadows and patterns of slate, wood shingles or tile. See also Dimensional Shingle.
ASHRAE: American Society of Heating, Refrigerating & Air-Conditioning Engineers, Inc.
Asphalt: A brownish-black solid or semisolid mixture of bitumens obtained from native deposits or as a petroleum byproduct, which is typically used in paving, roofing and waterproofing. Asphalt can be refined to conform to various roofing grade specifications:
Type I (Dead-Level) Asphalt: A roofing asphalt for use in roofs which do not exceed a ¼ in 12 slope (2%).
Type II (Flat) Asphalt: A roofing asphalt for use in roofs which do not exceed a ½ in 12 slope (4%).
Type III (Steep) Asphalt: A roofing asphalt for use in roofs which do not exceed a 3 in 12 slope (25%).
Type IV (Special Steep) Asphalt: A roofing asphalt for use in roofs which do not exceed a 6 in 12 slope (50%).
Asphalt Emulsion: A mixture of asphalt particles and an emulsifying agent such as bentonite clay and water.
Asphalt Felt: An asphalt-saturated and/or an asphalt-coated roofing felt. (See also Felt.)
ASTM: American Society for Testing and Materials.
Atactic Polypropylene (APP): The polymer that is added to asphalt in APP modified bitumen roofing that gives the material greater elasticity.
Back-Nailing: The method of fastening the back or upper side of a ply of roofing felt or other component in a roof system so that the fasteners are covered by the following ply.
Ballast: A material installed over the top of a roof membrane to help hold it in place, such as aggregate or concrete pavers.
Base Flashing: Plies of roof membrane material used to seal a roof at vertical plane intersections, such as roof-wall and roof-curb junctures (See also Flashing.)
Base Ply: The primary ply of roofing material in a roof system.
Base Sheet: An asphalt-impregnated or coated felt used as the first ply in some built-up and modified bitumen roof systems.
Batten: A strip of wood fastened to the structural deck or rafters for use in attaching a primary roof system, such as tile.
Bird Bath: A small, inconsequential amount of water that may accumulate on a roof, but quickly evaporates.
Bird Screen: Wire mesh installed over vents or other openings to prevent birds from entering a building or roof cavity.
Bitumen: Any of various flammable mixtures of hydrocarbons and other substances, whether occurring naturally or obtained by distillation from coal or petroleum, that are a component of asphalt and are used for roofing and waterproofing, as well as for surfacing roads.
Blind-Nailing: The use of nails so that they are not exposed to the weather in the finished roofing system. See Back-Nailing.
Blister: A pocket of air or water vapor trapped between layers of roofing felt or membrane.
Blocking: Pieces of wood that are built into a roof assembly to stiffen the deck around an opening, support a curb, or to serve as nailers for the attachment of membranes or flashings.
Blown Asphalt: See Air Blown Asphalt.
Blueberry: A small bubble found in the flood coat of an aggregate-surfaced built-up roof. See also Tar Boil.
Boot: A piece of preformed material designed to protect roof penetrations from dirt, moisture and other foreign and/or damaging substances.
Brooming: Embedding a ply of roofing material into hot bitumen or adhesive by using a broom, squeegee, or other piece of equipment to eliminate voids and help ensure adhesion.
Built-Up Roof: A roof membrane consisting of layers of bitumen, which serves as the waterproofing component, with plies of reinforcement fabric installed between each layer. The reinforcement material can consist of bitumen-saturated felt, coated felt, polyester felt or other fabrics. A surfacing is generally applied to complete the roof system. Common surfacings include asphalt, aggregate, emulsion and granule-surfaced cap sheets.
Bundle: An individual package of shingles or shakes.
BUR: An acronym for Built-Up Roof.
Butt Joint: Where two separate, adjacent pieces of material abut.
Cant Strip: A triangular-shaped strip of material used to ease the transition from a horizontal plane to a vertical plane. Cant strips can be made of wood, wood fiber, perlite or other materials.
Cap Flashing: A material used to cover the top edge of base flashings or other flashings. (See also Coping).
Cap Sheet: A granule-surfaced membrane often used as the top ply of BUR or modified bitumen roof systems.
Caulk: A material with no elastomeric properties that is used for sealing joints.
Caulking: The act of sealing a joint.
Cellulose: A complex carbohydrate that is the main constituent of the cell wall in most plants, and is used in the manufacturing of organic roofing materials.
Chopped Glass and Emulsion (CG&E): A roof coating that consists of asphalt or clay emulsion and glass fiber reinforcement.
Cladding: A material used to cover the exterior wall of a building.
Cleat: A continuous metal strip used to secure two or more metal roof components together.
Closed-Cut Valley: A method of valley application in which shingles from one side of the valley extend across the valley while shingles from the other side are installed over the top of those and then trimmed back from the valley centerline.
Coal Tar Pitch: A type of coal tar used in dead-level or low-slope built-up roofs. Because of its tight molecular structure, coal tar pitch is very resistant to corrosive environments and virtually impervious to standing water.
Coated Base Sheet: An asphalt-saturated base sheet membrane that is later coated with harder, more viscous asphalt, thereby increasing its impermeability to moisture.
Coated Felt: An asphalt-saturated ply sheet that has also been coated on both sides with harder, more viscous asphalt.
Cold Process Built-Up Roof: A roof consisting of multiple plies of roof felts laminated together with adhesives that do not require heating.
Composition Shingle: A type of asphalt shingle used in steep-slope roofing and generally comprised of weathering-grade asphalt, a fiber glass reinforcing mat, an adhesive strip, and mineral granules.
Concealed-Nail Method: A method of installing asphalt roll roofing material in which all nails or fasteners are driven into the underlying roofing and then covered by an overlapping course.
Cool Roof: A roofing material certified by the Cool Roof Rating Council as having a minimum solar reflectance of at least 0.70 and a minimum thermal emittance 0.75. The use of a “cool” roofing material can increase a building’s energy efficiency by reducing the surface temperature of the roof, which in turn reduces the air conditioning load on the building.
Coping: A piece of material used to cover the top of a wall and protect it from the elements. Copings can be constructed from metal, masonry or stone.
Counter Batten: Wood strips installed vertically on sloped roofs over which horizontal battens are secured.
Counterflashing: Formed metal sheeting secured to walls, curbs, or other surfaces, for use in protecting the top edge of base flashings from exposure to weather.
Course: The term used for each row of roofing material that forms the roofing or flashing system.
Crack: A separation or fracture occurring in a material. See also Split.
Creep: Movement of the roof membrane that can cause the roof system to deform.
Cricket: A roof component used to divert water away from curbs, platforms, chimneys, walls or other roof penetrations and projections. See also Saddle.
Curb: A raised member used to support skylights, HVAC units, exhaust fans, hatches or other pieces of mechanical equipment mounted above the level of the roof surface. A curb should usually be a minimum of eight inches (8″) in height.
Cutback: Bitumen thinned by solvents that is used in cold-process roofing adhesives, roof cements, and roof coatings.
Cutout: The open area between shingle tabs.
Dampproofing: Treatment of a surface or structure to resist the passage of water in the absence of hydrostatic pressure.
Dead Level: A roof with no slope or pitch.
Dead-Level Asphalt: Asphalt for use in roofs which do not exceed a ¼ in 12 slope (2%).
Dead Loads: Permanent, non-moving loads on a roof resulting from the weight of a building’s components, equipment, and the roof system itself.
Deck: The structural component of the roof of a building which provides the substrate to which the roofing system is applied.
Deflection: The downward displacement of a structural member under load.
Delamination: Separation of laminated layers of a material or system.
Dimensional Shingle: A shingle that is textured or laminated to produce a three-dimensional effect. Also known as Laminated and Architectural Shingles.
Dimensional Stability: The ability of a material to retain its current properties and to resist a change in size resulting from exposure to temperature changes and moisture.
Dome: A roof with a partial-spherical shape.
Dormer: A framed projection through the sloping plane of a roof.
Downspout: A conduit for carrying water from a gutter, scupper, drop outlet or other drainage unit from roof to ground level.
Drain: A plumbing fixture designed to remove water from a roof by gravity.
Drip Edge: A steel flashing bent at a 90º angle that is placed along the outer perimeter of steep sloped buildings and used to help direct runoff water away from the building. Drip Edge resembles nosing, except that it has an outwardly-angled bottom edge.
Dry Rot: Wood rot caused by certain fungi. Dry rot can result from condensation build-up, roof leaks that go untended, or from other problems. Dry rot will not remain localized. It can spread and damage any lumber touching the affected area.
Eave: A roof edge that extends out past the exterior wall line.
Edge Stripping: Roofing material used to seal perimeter edge metal and the roof itself.
Elastomeric: A material that will return to its original shape after being stretched.
Elastomeric Coating: A coating with elastomeric properties.
Emulsion: Fine particles suspended in a liquid solution.
End Lap: The extension of one component of material past the end of an adjacent piece of material.
Equipment Screen: A nonstructural wall or screen constructed around rooftop equipment such as HVAC units, curbs, etc. to hide the equipment from view and make the structure more aesthetically pleasing.
Equiviscious Temperature (EVT): The temperature at which bitumen attains the proper viscosity for use in built-up roofing. The EVT is usually expressed as a range, with a twenty-five degree Fahrenheit (25° F) variance permitted above and below the recommended EVT.
Expansion Joint: A built-in separation between building sections to allow for free movement between the sections without damaging the building’s structural components.
Exposed-Nail Method: A method of installing roll roofing materials where all nails/fasteners are visible and exposed to the elements.
Exposure: The portion of the membrane that is not overlapped by the succeeding ply or course. Or, the portion of the roofing material exposed to the weather after being installed.
Fallback: A reduction in the softening point temperature of asphalt that occurs when asphalt is overheated for prolonged periods of time.
Fascia: Vertical roof trim located along the perimeter of a building, usually below the roof level. Its use can be either decorative or for waterproofing.
Felt: A roofing sheet made of interwoven fibers.
Felt Machine: A machine used to install built-up roofing by dispensing bitumen and felt at the same time.
Fiberglass Insulation: Rigid boards or blankets composed of glass fibers that are used to insulate roofs and walls.
Field of the Roof: The central part of a roof, away from the perimeter.
Fishmouth: An opening along the exposed edge of an installed ply of felt caused by shifting of the ply during installation.
Flash: To install flashing components.
Flash Point: The lowest temperature of a liquid material at which combustion will occur when air reaches its surface.
Flashing: Components used to seal the roof system at areas where the roof covering is interrupted or terminated. For example, pipes, curbs, walls, etc. all have special components that, when correctly installed, will help prevent moisture entry into the roof system or building.
Flood Coat: The surfacing layer of bitumen into which aggregate is embedded on an aggregate-surfaced built-up roof.
Gable: A triangular-shaped portion of the endwall of a building located directly under the sloping roof and above the eave line.
Galvanized Steel: Steel that is coated with zinc to aid in corrosion resistance.
Gambrel: A roof that has two different pitches.
Glaze Coat: The uppermost layer of asphalt on a smooth-surfaced built-up roof membrane.
Granule: A small aggregate, naturally or synthetically colored, that is used to surface cap sheets, shingles, and other granule-surfaced roof coverings.
Gravel: Aggregate consisting of rock fragments or pebbles.
Gravel Stop: A flanged, sheet metal edge flashing with an upward projection installed along the perimeter of a roof to prevent loose aggregate from falling over the roof edge to the ground or level below.
Green Roof System: A system of plantings and/or landscaping installed above a waterproofed substrate at any building level that is separated from the ground beneath it by a man-made structure. A green roof system consists of a waterproofing system and its associated components, such as a protection course, a root barrier, a drainage layer, thermal insulation and an aeration layer, and an overburden of growth medium and plantings.
Gutter: A channel, usually made of sheet metal, that is installed along the downslope perimeter of a roof to convey water from the roof to the drain leaders or downspouts.
Half Gable Roof: See Shed Roof.
Headlap: The distance that the topmost ply of roofing felt overlaps the undermost ply or course.
Heat Welding: Fusing the seams of separate sections of roofing material together through the use of hot air or an open flame and pressure.
Hip: The angle formed by the intersection of two sloping roof planes.
Hip Roof: A roof that rises by inclined planes on all sides of a building. The line where two adjacent sloping sides of a roof meet is called the hip.
Hoist: A mechanical lifting device. A hoist can be hand or electrically operated.
Holiday: An area where a liquid-applied material is missing.
Hot: Slang for hot bitumen.
HVAC: Acronym for Heating, Ventilating, and Air Conditioning.
Impact Resistance: A roof assembly’s ability to withstand damage due to falling objects, such as hail.
Infrared Thermography: The use of an infrared camera to detect moisture in a roof system.
Insulation: Material used to increase the energy efficiency of a building by reducing the flow of heat to and from that building. See also Thermal Insulation.
Interlayment: A material that is usually installed between adjacent rows of wood shakes to enhance the roof’s ability to prevent water intrusion.
Interlocking Shingles: Shingles that lock together to provide better wind resistance.
Inverted Roof Membrane Assembly (IRMA): A roof assembly in which the insulation and ballast are placed on top of the roof membrane, rather than beneath it. Also known as a Protected Membrane Roof.
Jack: See Roof Jack.
Joint Tape: Tape used to seal joints between insulation boards.
Joist: Any of the parallel horizontal beams set from wall to wall to support the boards of a floor, ceiling or roof of a building.
Laminated Shingles: See Dimensional Shingles or Architectural Shingles.
Lap: The part of the roofing material that overlaps a section of adjacent material.
Lead: A common metal used for flashing material.
Live Loads: Temporary items on a roof such as people, snow, etc. which the roof must be designed to support.
Loose-Laid Roof Membranes: Roofing material that is only attached at the perimeter and at penetrations and held in place by ballast, pavers, or other materials.
Mansard: (1) A steep-sloped roof located at the perimeter of a building and usually used for decorative purposes; (2) The upper story formed by the lower slope of a mansard roof.
Mansard Roof: A steeper roof that terminates into a lower sloped roof at its high point.
Mastic: A thick adhesive material used as a cementing agent for holding a roofing or waterproofing membrane in place.
Material Safety Data Sheet (MSDS): Information provided by a manufacturer that describes the characteristics of chemicals in a given product, as well as other information such as emergency procedures and safe handling.
Mechanical Damage: Damage to a roof by means of items puncturing or otherwise unnecessarily penetrating the roof system or any of its components.
Mechanical Fasteners: Devices such as screws, plates, battens, nails, or other materials that are used to secure roofing materials to the deck.
Membrane: The portion of the roofing system that serves as the waterproofing material. A membrane can be composed of one material or several materials laminated together.
Metal Flashing: Roof components made from sheet metal that are used to terminate the roofing membrane or material along roof edges. Metal flashings are also used in the field of the roof around penetrations.
Mineral Fiber: Inorganic fibers of glass or rock.
Mineral Granules: See Granules.
Mineral-Surfaced Roofing: Roofing materials with a top surface consisting of mineral granules.
Modified Bitumen: A bitumen modified by the addition of one or more polymers, such as Atactic Polypropylene (APP) or Styrene Butadiene Styrene (SBS), to enhance its natural properties, especially elasticity.
Mopping:To apply hot asphalt or coat tar using a hand mop or mechanical applicator.
Nailer: A piece of lumber that is secured to the deck, walls, or curbs to receive fasteners for roof membranes.
Nailing Pattern: The specific method or pattern at which nails are to be applied.
Nesting: To overlay existing shingles with new shingles and butt the top edge of the new shingle up against the bottom edge of the existing shingles.
Nosing: Metal flashing bent at a 90º angle and installed around roof perimeters, curbs, platforms, etc. in order to protect the edge of the roofing system. Nosing should not be used in place of drip edge.
NRCA: National Roofing Contractors Association.
Open Valley: A valley where both sides of the roofing material are trimmed back from the centerline to expose the valley flashing material beneath.
Organic Felt: An asphalt roofing base material manufactured from cellulose fibers.
Organic Shingle: An asphalt shingle reinforced with organic material manufactured from cellulose fibers.
OSB: Oriented Strand Board, which is often used as roof sheathing in place of plywood.
Overlay: See Re-Cover.
Overspray: The loss of spray particles (from coatings, SPF, etc. ) in the air.
Pan Flashing: A sheet metal flashing that covers an equipment platform and is designed to counterflash the base flashings surrounding the platform.
Parapet Wall: That part of a perimeter wall that extends above the surface of the roof.
Penetration: Any object that pierces the surface of the roof.
Perlite: A natural volcanic glass that is used in lightweight insulating concrete and fire-resistant rigid insulation board.
Pipe Boot: A prefabricated flashing piece that is used to flash around circular pipe penetrations. Also known as a Roof Jack.
Pitch: A term used to describe Roof Slope. Also shorthand for Coal Tar Pitch.
Pitch Pocket (a.k.a. Pitch Pan): A flanged piece of flashing material placed around irregularly shaped roof penetrations and filled with grout and a pourable sealer to seal around the penetration to prevent moisture entry.
Ply: A layer of felt or other reinforcement material in a roof system.
Polymer Modified Bitumen: See Modified Bitumen.
Ponding: The accumulation of water at low-lying areas on a roof.
Positive Drainage: The drainage condition of a roof where all water is gone from the roof surface within forty-eight hours of precipitation under normal drying conditions.
Press Brake: A mechanical device used to form sheet metal into desired shapes and profiles.
Primer: A material that is applied to a surface in order to increase that surface’s ability to adhere to or work in conjunction with a subsequently applied material.
Protected Membrane Roof Assembly (PMRA): A roof assembly in which the insulation and ballast are placed on top of the membrane. Also known as an Inverted Roof Membrane Assembly (IRMA).
Purlin: A horizontal secondary structural member used to transfer loads from the primary structural members.
R-Value: The measure of a material’s resistance to heat flow. The higher a material’s R-value, the more it insulates.
Rake: The sloped perimeter edge of a roof that runs from the eaves to the ridge. The rake is usually perpendicular to the eaves and ridge.
Re-Cover (Overlay): The installation of a new roof system directly over an existing roof system.
Reglet: A receiver, usually made of sheet metal, to which counterflashings are attached. Reglets can be surface-mounted or part of the wall assembly.
Re-roofing: The procedure of installing a new roof system on an existing building.
Ridge: The line where two planes of roof intersect, forming the highest point on the roof that runs the entire length of the roof.
Ridge Cap: Material applied over the ridge or hip of a roof.
Ridge Vent: An exhaust venting device located at the ridge of a roof.
Roll Goods: The term used for all roofing materials that come in rolls.
Roof Assembly: A term used to describe all of the components of a roof system, including the structural roof deck.
Roof Curb: A frame or platform on which rooftop equipment such as HVAC units, exhaust fans, skylight, etc. is mounted.
Roof Jack: (1) A steel bracket fastened to the roof that is used to support toe boards; (2) A term used to describe a Pipe Boot.
Roof Slope: The angle made by the roof surface plane with the horizontal plane and expressed as the amount of vertical rise for every twelve inch (12″) horizontal run. For instance, a roof that rises four inches (4″) for every twelve inch (12″) horizontal run, is expressed as having a “four in twelve” slope; often written as “4:12.” Expressed as a percentage, the slope would be 33%, which is equal to 4 divided by 12. Also known as the Pitch of a roof.
Roof System: Multiple roof components assembled to provide waterproofing (and sometimes insulating) capabilities for a structure.
Saddle: A small, somewhat pyramid-shaped structure erected in between roof drains that is used to direct run-off water toward the drains.
SBS: See Styrene Butadiene Styrene.
Sealant: A generic term for a multitude of materials used to seal joints or junctures against moisture or weather.
Seam: A line, ridge, or groove formed from fitting, joining or lapping two sections together.
Self-Adhering Membrane: A type of membrane whose bottom surface will stick or adhere to a substrate without the use of an additional adhesive material.
Self-Sealing Shingle: Asphalt shingles with adhesive strips on the back that will soften and stick to the following course of shingles when heated by the sun. Self-sealing helps to increase resistance to wind uplift.
Shed Roof: A roof with only one sloping plane. Also known as Half Gable.
Shingle: A single piece of prepared roofing material, either asphalt or wood, for use in steep slope roof systems.
Side Lap: The longitudinal overlap of neighboring materials.
Single-Ply Membranes: Roofing membranes that are applied in one layer. Seams of single-ply membranes can be heat welded, solvent welded or and adhered using seam tape or other adhesives.
Slate: A fine-grained metamorphic rock that splits into thin, smooth-surfaced layers used in steep slope roofing applications.
Slope: The angle of incline of a roof expressed as a percentage or as a ratio of rise to run. See Roof Slope.
Smooth Surfaced Roof: A roof with no surfacing or with a smooth surfacing such as emulsion or a reflective coating.
Soffit: The underside of a roof overhang.
Soffit Vent: An intake ventilation device located in the soffit.
Softening Point: The temperature at which bitumen will begin to flow.
Solar Reflectance: A measure, expressed as a number between 0 (low) and 1 (high) of the ability of a material to reflect sunlight, including visible, infrared and ultraviolet wavelengths.
Solid Mopping: To continuously apply hot asphalt or coal tar, leaving no areas without bitumen.
Solvent: A liquid capable of dissolving other substances, such as bitumen.
Solvent Weld: To weld materials using a liquid solvent.
Split: The separation of a material resulting from tensile forces.
Sprayed Polyurethane Foam (SPF): A monolithic sprayed-on roofing material with a high R-value, which is formed when isocyanate (“A” component) and resin (“B” component) are mixed.
Sprinkle Mopping: To scatter hot bitumen over a surface.
Spud: To remove the top surfacing of a roof by scraping it with special tools called spud bars or power spudders.
Spud Bar: A long-handle tool with a stiff flat blade on one end (usually 4″ or 6″ wide) that is used to scrape and remove the top surfacing of a roof down to the membrane.
Square: 100 square feet of roof area.
Standing Seam: A type of metal roof system where the longitudinal seams on adjacent panels are turned up, overlapped and folded in various ways in order to prevent moisture entry and interlock the panels.
Starter Course: The primary course of roofing material. The starter course is installed along the downslope perimeter edge and usually covered by the first course of roofing.
Starter Plies: Felt or ply sheets that are cut into widths that are proportionate to the reciprocal of the number of plies being installed. For instance, with a three-ply built-up roof, the first starter ply would be one-third of the roll width, the second two-thirds of the roll width installed over it, and then a full ply over those.
Steep Asphalt: A roofing asphalt that can be used on roofs with slopes up to 3 in 12 (25%).
Steep-Slope Roof: A roof with a slope greater than or equal to 3 in 12 (25%).
Steep-Slope Roofing Materials: Roofing materials (such as asphalt shingles, wood shakes, tile and slate) that depend on their water-shedding capabilities to keep moisture from entering a building. These materials are generally installed on roofs with slopes that equal to or exceeding 3 in 12 (25%).
Step Flashing: Pieces of metal or other material that are used to flash roof projections such as chimneys, walls, curbs, etc. The pieces are installed between each course of roofing and generally have a vertical flange equal in length to that of the horizontal flange.
Styrene Butadiene Styrene (SBS): The polymer that is added to SBS modified bitumen roofing that gives the material a rubber like quality.
Substrate: The surface that the roof is installed upon.
Surfacing: The top-most layer of the roof system.
Tar Boil: A small bubble found in the flood coat of an aggregate-surfaced built-up roof that is usually the result of trapped moisture vapor. Tar Boils are also known as blueberries.
Tear-Off: To remove a roof system down to the substrate.
Termination: The sealed edges of a roof membrane.
Termination Bar: A bar, usually made of metal or vinyl, that is used to seal and anchor the free edges of a roof membrane.
Thermal Emittance: A measure, expressed as a number between 0 (low) and 1 (high), of the ability of a material to release absorbed heat.
Thermal Insulation: A material used to reduce heat flow into and out of a building.
Thermal Movement: Expansion and contraction of a roofing material resulting from temperature changes.
Thermal Resistance (R): The measure of a material’s ability to resist heat flow. The higher a material’s R-value, the better it insulates.
Thermoplastic: A type of roofing membrane material that can be repeatedly softened by heating and hardened by cooling. Thermoplastic membranes are typically seamed by heat welding with hot air or solvents. Polyvinyl chloride (PVC) and Thermoplastic Olefin (TPO) are the most common thermoplastic roof membranes.
Thermoset: Unlike a thermoplastic membrane material, a thermoset membrane material incorporates polymers that are chemically cross-linked or vulcanized. Once they “set”, they cannot be re-softened or re-shaped by heating. They can only be bonded to similar materials with adhesives. Ethylene Propylene Diene Monomer (EPDM) is the most common thermoset roof membrane.
Through-Wall Flashing: A material that extends through a wall and is used to direct water entering a wall cavity to the exterior of the structure.
Tie-In: The joining of two different roof systems.
Tie-Off: A watertight seal used to terminate roof membranes at system adjuncts, terminations, flashings or substrates.
Title 24: That part of the California Code of Regulations that sets forth the State’s building standards (electrical, fire, general building, mechanical, plumbing, etc.), as well as the California Energy Code. Among California roofing contractors, use of the term “Title 24” is usually shorthand for the Cool Roofing requirements contained in the Energy Code.
Traffic: Any rooftop activity that can potentially damage the roof surface.
Underlayment: A material installed over the roof deck prior to the application of the primary roof covering. Underlayment usually consists of fifteen- or thirty-pound felt, but ice and water protection membrane can also be used for this purpose.
Underwriters Laboratories (UL): A non-profit agency which functions as the testing arm of the National Board of Fire Underwriters. UL maintains laboratories for the examination and testing of various devices, systems, and materials to determine their safety against the hazards of fire, wind, and accidents.
Uplift: See Wind Uplift.
Upside Down Roof: See Protected Membrane Roof.
Valley: The internal intersection of two sloping roof planes that runs from the eaves to the ridge. This intersection collects the most water run-off.
Vapor Retarder: A material used to restrict the passage of water vapor through a roof assembly.
Viscosity: The resistance of a material to heat flow.
Viscous: Having a fairly high resistance to heat flow.
Void: An open space or a break in continuity; a gap.
Waterproofing: The treatment of a surface or structure in order to prevent the passage of water under hydrostatic pressure.
Weather: To undergo degradation in quality and appearance due to exposure to the sun, wind, rain, etc.
Weep Holes: Small holes used to permit moisture that has gathered inside a building component to drain.
Wick: To convey liquid by capillary action.
Wind Clip: A clip that slips over the ends of tile, slate and other steep slope roofing materials in order to help secure them and resist wind uplift.
Wind Load: The force that wind puts on structures.
Wind Uplift: The upward displacement of a roof system or section thereof caused by the movement of air across the surface of a roof.
Wire Tie: A system for attaching heavy steep slope roofing materials, such as slate or tile, by using wire fasteners in addition to or in place of nails.
Woven Valley: A valley construction whereby the valley has a woven look, which is achieved by overlapping alternate courses of shingles from both sides of the valley.
Z- or Z-Section: A piece of steel formed in the shape of a “Z.”
Zinc: A bluish-white, lustrous metallic element that is brittle at room temperature but malleable when heated. In roofing, zinc is a common component of a variety of alloys used to make gutters, flashings and edge metals.