A

Absorption: A material’s ability to take in gases or liquids and incorporate them within its body.

Accelerated Weathering: When materials in a controlled environment have exposure to heat, light, water, or condensation in an altered state so that their effects get magnified, they tend to weather at a rapid pace. After this accelerating weathering process, the exposed material’s physical properties will be compared to those of the original unexposed material or that which has gone through natural weathering.

Adhere: When two surfaces bond together, it is called adhesion — for example, asphalt layers and cement membranes in BUR roofing.

Aggregate: Materials like stone, crushed stone, rock, water-worn gravel, crushed slag, or marble chips make up the top surface or as ballast in a roofing system.

Aging: Environmental effects on roofing materials that appear with time.

Alligatoring: Bitumen layers on a built-up roofing system produce a series of cracks that resemble an alligator’s hide on the surface or even the inner layers.

Aluminum: Rust-resistant metal used for flashing and in metal roofing systems.

Ambient Temperature: The temperature of the environment or air around an object.

Application Rate: The quantity of material- volume, mass, or thickness- used per unit area.

Apron Flashing: The flashing applied at the joint where the sloped roof connects to a much steeper roof or the vertical wall.

Architectural Shingle: A high-quality dimensional shingle that beautifies the roof appearance.

Asphalt: Sometimes known as bitumen, it is a highly viscous and sticky brown or black material found as a residue after crude oil or petroleum processing.

Asphalt Emulsion: Asphalt cement components are made less viscous in blending machinery, by adding water and emulsifying agents like bentonite clay.

Asphalt Felt: A uniform flexible felt made with asphalt-saturated material.

Asphalt Roof Cement: A solvent-based asphalt or bitumen used to apply on cracks and glue down loose shingles or other fibers to the roof surface.

Attic: Ventilated cavity or open space in the interior of the property, under a steep-sloped roof deck and above the ceiling.

B

Back-Nailing: A roofing felt is fastened with nails, connecting it to the next sequential ply or roof to secure it properly and protect it from slippage and weather exposure.

Ballast: An anchoring material that provides stability to the roof structure. It could be heavy substances like aggregates or concrete pavers, which keep the roof membranes in place.

Barrel Vault: A tunnel or vault made of a series of circular or rounded architectural elements that form the ceiling of a building.

Base Flashing: Flashing applied at the intersections of roof and wall or roof and vertical junctures to seal the joints and make them waterproof.

Base Ply: The first ply laid on the roof deck, which becomes the base membrane.

Base Sheet: In a multilayer or built-up roofing system, the base sheet is the bottom-most ply or membrane that is a waterproof, saturated, impregnated, or coated felt.

Batten: Battening or roofing lath can be a metal, wood, or plastic cap or closure set that covers the joints between adjacent panels. Usually, this is fixed over the roof deck to attach tiles, shingles, or base flashing in place.

Batten Seam: A traditional roof covering technique where a metal panel profile runs parallel to the roof, formed around a metal batten.

Bitumen: a black colored, highly viscous, and a semi-solid mixture of hydrocarbons obtained in the petroleum distillation process. This compound is found in asphalt, coal tars, pitches, and wood tars.

Blackberry: Typically, a tar boil that appears on the flood coating of the aggregate-surface in a BUR system.

Blind-Nailing: Driving nails into a finished roof at an angle so that they are not exposed to adverse weather conditions.

Blister: Small bubbles in the roofing membrane occurring due to trapped moisture, enclosed air pockets, loose adhesion, or improper installation of the roofing layers.

Blocking: Wood rafters built into the roofing system provide a stop for ceiling insulation. They lie below the flashing and above the roof deck, and act as a support to the curb.

BOMA: Building Owners & Managers Association

Brake: Manual or mechanical handling machinery that presses the metal.

British Thermal Unit (BTU): A traditional unit of thermal energy, equal to around 1055 joules. It is the quantity needed to increase the temperature of one pound of water by one degree Fahrenheit.

Brooming: The process of embedding a roofing ply material into a layer of hot bitumen with the help of a broom or squeegee. This process smoothes out the ply, making it adhere to the bitumen.

Buckle: A visible, elongated and upward lump that forms due to some movement in the roofing assembly or displacement in the roof deck joints or insulation.

Building Code: A set of regulations and ordinances with which a roofing structure must comply. A recognized agency in a designated jurisdiction prescribes the design loads, construction details, quality of materials, and procedures that must be followed for structures in that area.

Built-Up Roof Membrane (BUR): Multiple layers of fabrics, mats, coated, or saturated felts applied between alternating layers of bitumen form a continuous and semi-flexible roof membrane. The top surface of built-up roof membranes consists of bitumen and mineral aggregate or a granule-surfaced cap sheet.

Bundle: Shakes or shingles available in individual packages.

Butt Joint: Separate sections like materials of insulation, when placed adjacent to each other,  without overlapping, create a butt joint.

Button Punch: A button punch indents several thicknesses of metal pieces pressed together to secure them in place and to prevent slippage.

Butyl: An elastomeric polymer or synthetic rubber, a copolymer of isobutylene and isoprene. Used as primary binders, adhesives, and modifiers, it is available in sheet form, or as elastomeric blends.

Butyl Coating: An elastomeric roof restoration solution that prevents rust, seals metal roofs, and acts as a vapor barrier.

Butyl Rubber: An elastomer rubber based on isobutylene-isoprene copolymer. This high-performance product is impermeable to gases and moisture.

Butyl Tape: A high-performance butyl rubber compound used as an adhesive for metal roof panel seams, end laps and  to seal other sheet metal joints.

C

Camber: A slight convexity or curve of the roof deck surface, arch, or truss.

Canopy: An overhead roof, usually unsupported at the end, that is a projecting structure which protects the entrances or doors from sun, rain, hail, or snow.

Cant: Foam, wood, or other material in a beveling angle placed perpendicularly for joint strength and water runoff.

Cant Strip: A beveled and triangular-shaped material placed at the joining between a roof or an insulating and waterproof material and a vertical wall, so that the roof does not bend sharply and to facilitate the flow of water.

Cap Flashing: Flashing made of metal, which covers or shields the exposed and upturned edges of various building components like the base flashing and prevents water intrusion.

Cap Sheet: A multilayer sheet made of asphalt, tar, or fiberglass, used to create a water-tight surface. Also known as reinforced bitumen membranes, these are gravel coated surfaces and are used as the top plies.

Capillary Action: The movement of water or liquids between adjacent surfaces in contact, like panel side laps, due to surface tension.

Caulking: sealing a joint, seam, void, or juncture between two adjacent units using a sealant, and making it weather-tight.

Cavity Wall: A double wall with two vertical layers built with the purpose to create an air space within the structural framing. It has a lower heat-flow rate and allows moisture to drain.

CCF: 100 cubic feet.

Chalk: A powdery residue used to mark lines on the roof material.

Chalk Line: A line marked on the roof by snapping a taut string dusted with colored chalk; done for alignment purposes – for laying of shingles, etc.

Chalking: Residue that forms over time, on a roofing material – the degradation of paints, or coatings on a metal surface.

Chimney: A pipe projecting through the roof, made of stone, prefabricated metal, or wood, which allows for smoke and combustion gases from the interior to escape into the air.

Cladding: Roof cladding is a material that becomes the exterior layer of a building; it provides weather resistance and thermal insulation.

Cleat: A metal strip made of continuous or individual clips or plates, angled and used to secure roofing components together.

Closed-Cut Valley: A method of application of shingles where you extend them across the valley. The shingles on the other side of the valley get trimmed by about 2 inches from the centerline.

Closure Strip: Sections made of metal or any flexible material like neoprene foam seal the raised openings formed between metal sheets, panels, and flashings.

Coal Tar: A thick, black or brown colored, high-viscous hydrocarbon liquid formed as a by-product of the distillation of coal to make coke and coal gas. Refined coal tar pitch is an ingredient of built-up roof membranes.

Coal Tar Bitumen: For low-slope BURs or dead-level built-up roof membranes, Type III coal tar that conforms to ASTM D 450 is used for waterproofing and dampproofing. Coal Tar Bitumen is its proprietary trade name.

Coal Tar Pitch: Type I or Type III coal tar that conforms to ASTM D 450 used as the waterproofing agent for dead-level or low-slope BURs.

Coal Tar Waterproofing Pitch: Type II coal tar pitch that conforms to ASTM D 450, used in below-grade structures for waterproofing.

Coated Base Sheet: Asphalt impregnated or filled felt, which is later coated with more viscous and harder asphalt to make it more impermeable to moisture.

Closed-Cut Valley: A method of application of shingles where you extend them across the valley. The shingles on the other side of the valley get trimmed by about 2 inches from the centerline.

Closure Strip: Sections made of metal or any flexible material like neoprene foam seal the raised openings formed between metal sheets, panels, and flashings.

Coal Tar: A thick, black or brown colored, high-viscous hydrocarbon liquid formed as a by-product of the distillation of coal to make coke and coal gas. Refined coal tar pitch is an ingredient of built-up roof membranes.

Coal Tar Bitumen: For low-slope BURs or dead-level built-up roof membranes, Type III coal tar that conforms to ASTM D 450 is used for waterproofing and dampproofing. Coal Tar Bitumen is its proprietary trade name.

Coal Tar Pitch: Type I or Type III coal tar that conforms to ASTM D 450 used as the waterproofing agent for dead-level or low-slope BURs.

Coal Tar Waterproofing Pitch: Type II coal tar pitch that conforms to ASTM D 450, used in below-grade structures for waterproofing.

Coated Base Sheet: Asphalt impregnated or filled felt, which is later coated with more viscous and harder asphalt to make it more impermeable to moisture.

Coated Fabric: Fabrics coated and/or impregnated with a solution, powder, or molten, of protective acrylic, plastic, or similar material. Calendering process also results in coated fabrics, which have a top coat of a preformed film.

Coated Felt (Sheet): (1) an asphalt-impregnated felt coated with a more viscous and harder “coating” asphalt on both sides; (2) a glass fiber sheet simultaneously coated and saturated on both sides with asphalt.

Coating: Top layer that covers a surface to increase protection or for decoration, and then cured until it achieves an elastomeric consistency. Materials used for SPF can be liquids, semi-liquids, or roof mastics generally applied using a roller or brush or sprayed onto the surface.

Cohesion: The ability of the molecules of a substance to bond with other molecules of the same.

Cold Process Built-Up Roof: Alternating layers of roof cement applied with asphalt-solvent liquid and plies of felts, other reinforced sheets, or fabrics, laminated together with adhesives installed at slightly elevated temperature form a semi-flexible and continuous roof membrane.

Combustible: The ability of a substance to catch burn.

Compatible Materials: Two materials are compatible with each other when they have the ability to blend or attach without causing adverse reactions to the materials.

Composition Shingle: A unit of shingle roofing with an asphalt composition on the outer layer and on the underside, it has a fiberglass reinforcing mat that makes it waterproof.

Concealed-Nail Method: A method of application of asphalt roll roofing material where the nails are fastened to the underlying roofing and concealed by a cemented, overlapping course.

Condensation: The process where water vapor or any other gaseous substance converts into its liquid state with a drop in temperature drops or a rise in atmospheric pressure. (Also see Dew Point.)

Conductor Head: A custom fabricated part of the roof plumbing that is installed to the gutter system, lying between the downspout and a through-wall scupper. It acts as a catch basin for the run-off water downspout.

Contact Cements: Bonding material used to adhere to various roofing components. Contact cements or adhesives effectively create a permanent bond between the components immediately.

Contamination: Making surfaces or materials unclean or impure by adding undesirable foreign substances and rendering them unsuitable for its intended purpose.

Coping: A specially designed piece, typically made of masonry, stone, or metal, which covers the top of a wall that is exposed to the elements and protects the walls and flashing from moisture intrusion.

Copper: A malleable, ductile, and natural weathering metal, an important component used in metal roofing; usually of 16 or 20 ounces per sq.ft thickness.

Cornice: An ornamental horizontal molding located just below the roof, a projected roof overhang.

Counterflashing: Metal sheeting or barrier installed at the intersection of the roof and vertical walls, chimneys, or any vertical surface, to protect the flashing and associated fasteners from weather exposure and water infiltration.

Course: (1) A row of shingles installed on the roofing material; (2) number of layers of materials applied onto a roof surface (e.g., a five-course wall flashing consists of three layers of roof cement, each sandwiched by a layer of felt or fabric).

Coverage: The surface area where a particular roofing material is applied.

Cricket: A ridge structure in the roof or an elevated substrate constructed behind a chimney or a vertical wall to divert water away and prevent roof leaks. (See Saddle.)

Cross Ventilation: A natural cooling effect obtained when warm interior air escapes through a roof cavity and allows cool exterior air in through the vents.

Cupola: A dome-like structure crowning the ridge of the roof to increase ventilation.

Curb: (1) A roof member on an elevated level than the roof surface, which supports skylights, hatches, mechanical equipment, and more; (2) can also be a prefabricated raised roof perimeter that is relatively low in height.

Cure: A process in which a material is made to form permanent molecular bonds by exposing it to heat, pressure, chemicals, and/or weathering.

Cure Time: The time required for the curing process in which a material reaches its desirable physical characteristics, which it retains for a long while.

Cutoff: A permanent seal designed to isolate roofing sections and prevent lateral water movement in the insulation system. (Note: Not to be confused with a tie-off, which is either temporary or permanent.) (See Tie-Off.)

Cutout: The open gaps between the tabs of a strip shingle.

D

Dead Level: Also referred to as a zero-slope roof, the dead level is essentially a horizontal or flat roof deck that has no slope or slanting.

Dead Loads: Permanent non-moving loads on a roof resulting from the combined weights of structural and architectural components of a building. Mechanical and electrical equipment installed on the roof assembly is also “dead weights” or “deadweight loads.”

Deck: Roof deck of a building is the structural component that safely supports the design loads – both live and dead – including the roof systems and any additional live load requirements found in the building codes. The deck may be either non-combustible (e.g., concrete, gypsum, or corrugated metal) or combustible (e.g., wood or plywood.) It provides the substrate for waterproofing layers and the insulation system to be applied.

Deflection (Bowing, Sagging): Excessive load on the roof causes a downward displacement in its structure.

Delamination: A tear-off caused by trapped moisture between the laminated layers of a roof system.

Design Loads: The building has to be designed as per design loads – the specifications recommended by the federal, state, county, or city agencies.

Dew Point Temperature: The specific temperature where water vapor condenses and turns into liquid. At this point, the air has a relative humidity of 100% and condensation forms.

Dome: A curved roof of a hemispherical shape, oval, or other circular variations.

Dormer: A vertical framed projection constructed through and beyond the sloping roof.

Double Graveling: In tar-and-gravel roof systems or BURs, two layers of bitumen and gravel is applied. After the first coating is applied, loose aggregate will be swept away from the surface before the application of the second layer of bitumen and aggregate. This process ensures that approximately 50% of the applied second aggregate layer adheres to the bitumen flood coat permanently unless physically removed.

Double Lock Standing Seam: A standing seam between two panels that features an overlapping interlock, creating a double fold. (See Standing Seam.)

Downspout: A vertical pipe or other conduit attached to the side of the building that carries runoff water from a scupper, gutter, or conductor head to the ground, a lower level in the roof, or stormwater runoff system.

Drain: A device that collects the runoff water from the downspout and directs it away from the building.

Drip Edge: A metal sheet or other component overhanging the edge of the roof. It has an outward projecting metal flange which controls the flow of dripping water away from the underlying building components and protects them. A drip edge prevents capillary action by breaking the contact between wall components and the roof perimeter.

Dynamic Load: A non-static load that is changing its position, size, or direction, e.g., wind load.

E

Eave: Edge of a roof that overhangs the wall and projects beyond the side of the building.

Efflorescence: White-colored crystalline deposits left behind on the surface of stone, concrete, brick, or other surfaces when water evaporates from the masonry and salt remains. Adjacent concrete, grout, or mortar may also release free alkalies to form efflorescence.

Elastomeric Coating: A high build coating system that can be applied to the interior and exterior walls and helps protect masonry surfaces. When fully cured, the elastomeric coating has the capability of 100% elongation and can recover to its original dimensions.

EPDM: Ethylene Propylene Diene Monomer (See also Ethylene Propylene Diene Terpolymer.)

Expansion Joint: A structural assembly designed to facilitate the free movement between two building elements and withstand heat-induced expansion and reduction without causing any damage to the roof or waterproofing system.

Exposed-Nail Method: A method of application of asphalt roll roofing where the nails are visible and exposed to the weather. Nails are fastened to the cemented overlapping course.

Exposure: (1) The part of the roofing component that is open to weather and not overlapped by another component of the roofing system. For example, to compute the exposure of a ply in a shingled, four-ply BUR membrane, divide the felt width 36 inch (914mm) by the number of shingled plies to get the individual felt width and remove 2 inches (51mm) to get the exposure of wide felt, which is approximately 8 1/2 inches (216mm); (2) The unconcealed portion of the sidewall that is not overlapped by the upslope side of the roof, which is 5 inches (127mm) for a standard-size, 3-tab shingle roof.

Extrusion: A manufacturing process where batched and formulated molten material is forced through an orifice known as “die.” The finished product varies in shape and size, depending on the shape and dimensions of this die. Extrusion is used to manufacture a few types of single-ply roofing membranes.

Eyebrow: A small-sized dormer, whose roofline that projects beyond the upright face is in an arched shape and turns into a reverse curve before it meets the horizontal on both ends. Also, a shed roof projecting from the main roof area at the gable end.