Roofing Glossary

A coating system with an acrylic resin base.

The bonding of one surface to another.

The state of adhering.

Shrinkage cracking of the bituminous surface of built-up roofing, or the exposed surface of smooth-surfaced roofing, in which the loss of volatile oils and the oxidation pf compounds under solar radiation produces a pattern of deep cracks with the scaly look of an alligator's hide. It occurs only in unsurfaced bitumen exposed to the weather.

Sheet steel with a thin aluminum coating on the surface to enhance the corrosion resistance.

A non-ferrous metal used in roofing and fabrication of gutters and flashings. It is highly resistant to corrosion and lightweight.

An incombustible fibrous mineral form of magnesium silicate formerly used for fireproofing and sometimes used for the reinforcement of roofing materials.

A dark brown to black, highly viscous, hydrocarbon produced from the residue left after the distillation of petroleum, used as the waterproofing agent of a built-up roof. It comes in a wide range of viscosities and softening points - from about 135F (dead level asphalt) to 210F or more (special steep asphalt.)

A reinforcing fabric membrane made by asphalt coating or saturating a paper, fiberglass, or polyester mat typically for use in a built-up roof system..

Plies of roof membrane material used to seal a roof at the vertical plane intersections, such as at a roof-wall and roof-curb junctures.

A saturated and coated felt placed as the first ply in a multi-ply built-up roofing membrane.

The generic term for an amorphous, semisolid mixture of complex hydrocarbons derived from petroleum or coal. In the roofing industry, there are two basic bitumens: asphalt and coal tar pitch. Before application, they are (1) heated to a liquid state, (2) dissolved in a solvent, or (3) emulsified.

A spongy, raised portion of a roofing membrane, ranging in size from 1" in diameter and barely detectable height to as much as 50 sq. ft. in area and 1 ft. high. Blisters result from the pressure of entrapped air or water vapor.

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 and can be asphalt, aggregate, emulsion or a granule surfaced cap sheet.

Abbreviation sometimes used for built-up roofing membranes.

A continuous strip of triangular cross section, fitted into the angle formed by a roof deck and a wall or other vertical surface. The 45-degree slope of the exposed surface of the cant strip provides a gradual transition for base flashing and roofing membrane from a horizontal roof surface to a vertical surface.

A mineral-surfaced coated felt used as the top ply of a built-up roofing system.

The act of sealing a joint between two surfaces with an elastomeric compound.

A proprietary trade name for Type III coal tar used in dead-level or low-slope built-up roofs. It in not for use in roofs exceeding 1/4" in 12" (2%) slope.

A black solid hydrocarbon obtained from the residue of the distillation of coke-oven tar, used as the waterproofing agent of dead level or low slope built-up roofs. It comes in a narrow range of softening points - from 140 to 155F.

A bituminous membrane comprising of layers of coated felts bonded with cold applied asphalt roof cement and surfaced with a cutback(solvent based) or emulsified asphalt roof coating.

A box-shaped sheet metal component used to direct water from a through-wall scupper to a downspout. Also known as a Collector Head.

The piece of material used to cover the top of a wall and protect it from the elements. It can be constructed from metal, masonry, or stone.

A roof component used to divert water away from curbs, platforms, chimneys, walls, or other roof penetrations and projections.

A raised member used to support skylights, HVAC units, exhaust fans, hatches or other pieces of mechanical equipment above the level of the roof surface.

A built-up roofing membrane failure characterized by separation of the felt plies, sometimes resulting in wrinkling and cracking.

A conduit for carrying water from a gutter, scupper, drop outlet or other drainage unit from roof to ground level.

A device used to carry water off a roof.

Having elastic properties, capable of expanding or contracting with the surfaces to which the material is applied without rupturing.

Ethylene Propylene Diene Monomer, a rubber compound used to produce roof membranes and many other products.

A provision in design intended to allow movement to occur within a structure at a predetermined location.

Vertical roof trim located along the perimeter of a building, usually below the roof level. It's use can be either decorative or for waterproofing.

Devices used to secure roof system components.

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 (organic felts), asbestos fibers (asbestos felts), or glass fibers (glass-fiber felts).

A metal sleeve used as a spacer to keep gutter from being deformed when secured to the fascia with spikes.

Insulation composed of glass fibers used to insulate walls and roofs. It can be rigid board or blanket insulation.

An opening formed by an edge wrinkle in a sheet where it overlaps another sheet in a roofing membrane.

Connecting materials that seal the roof membrane at expansion joints, drains, gravel stops, and other places where the roof membrane is interrupted. Base Flashing forms the upturned edges of the watertight membrane at curbs and walls. Cap or counterflashing shields the exposed top edges of the base flashing.

A trowel-able, plastic mixture of bitumen, reinforcing fibers, and solvent.

A water test performed to determine the effectiveness of a roof covering..

Steel that is coated with zinc to aid in corrosion resistance. Galvanized steel for use in roofing should be Hot-Dipped Galvanized with a G-90 (1.25 oz/s.f.) coating.

A standard measurement. For instance the thickness of sheet metal or the diameter of wire. The thicker the wire or metal the lower the gauge.

In the manufacturing of roofing materials - a sheet comprised of bonded glass fibers before being saturated with bitumen.

Aggregate consisting of rock fragments or pebbles.

Flanged device, usually metal, designed to prevent loose aggregate from washing off the roof and to provide a finished edge detail for the roofing assembly.

A channel (usually sheet metal) installed along the down-slope perimeter of a roof to convey runoff water from the roof to the drain leaders or downspouts.

Fusing the seams of separate sections of roofing material together through the use of hot air or an open flame and pressure .

Roofer's term for hot bitumen.

A material used to help maintain a certain temperature in a building by reducing the flow of heat from and to the building.

The part of the roofing material that overlaps a section of the adjacent material.

Where two materials that overlap are sealed together.

Metal used for flashing material.

Roofing material attached only at the perimeter and at penetrations and held in place by ballast, pavers, or other materials.

The portion of the roofing system that serves as the waterproofing layer. Can be composed of one material or several materials laminated together.

Building 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.

An asphalt-saturated felt, coated on one or both sides and surfaced in the weather-exposed side with mineral granules.

a bitumen modified by one or more polymers, such as Atactic Polypropylene (APP) or Styrene Butadiene Styrene (SBS).

A vent installed through the roofing membrane to relieve moisture vapor pressure that has been trapped with the roofing system.

A survey of a roof specifically to detect the amount of moisture present in the roof system. Infra-Red, electronic capacitance, and nuclear detection are three methods used in roof moisture surveys.

An application of bitumen applied hot with a mop or mechanical applicator to the substrate or to the felts of a built-up roofing membrane.

A piece of lumber, preferably treated, that is secured to the deck, walls, or to pre-manufactured curbs. Nailers are used to receive fasteners for roof systems.

Refers to a specific method or pattern at which nails are applied. For instance, a nailing pattern for base sheets on plywood roof decks can be "Nine and Eighteen". This means one of nails on the outside edge of the sheet set at nine inches (9") on center, and two rows in the center of the sheet, each set at eighteen inches (18") on center.

The part of a perimeter wall that extends above the surface of the roof.

Any object that projects through the surface of the roof.

A prefabricated flashing piece used to flash around circular pipe penetrations.

A flanged, metal container placed around a column or other roof-penetrating element and filled with bitumen or other sealant to seal the joint.

A type of sealant that is initially in liquid form commonly used in conjunction with pitch pans to form a watertight barrier around penetrations that are difficult to flash.

A material that is applied to a surface to increase the bond strength of an adhesive to the surface.

Polyvinyl chloride, a thermoplastic resin used in the manufacture of many single ply roof membranes.

The measure of a material's resistance to heat flow. The higher the R-value, the more effective its insulating property.

The installation of a new roof system over an existing system without removing an existing system.

Felt that has been saturated with bitumen.

A vertical standing seam between two metal panels with one overlapping fold, as distinguished from a double-locked seam, which is folded twice.

Roofing membranes that are applied in one layer. Thermoplastic and thermoset(rubber) membranes are usually Single-Ply Membranes. Single-Ply membranes come in five basic types: (1) Ballasted, (2) Fully Adhered (3) Mechanically-Fastened (4) Partially Adhered, and (5) Self-Adhered. Seams of Single-ply Membranes can be heat welded, solvent welded, and adhered using seam tape or other adhesives.

A roofing membrane surfaced with a layer asphalt or cold-applied asphalt-clay emulsion or asphalt cutback, or a synthetic coating.

A continuous application layer of bitumen without voids.

A membrane tear resulting from tensile stress.

To remove the top surfacing of a roof by scraping it with special tools called spud bars to power spudders.

A roof area of 100 sq. ft.

A highly corrosion resistant steel alloy containing either chromium, nickel, or copper.

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.

(1) The technique of sealing the joint between metal and roof membrane with one or two plies of flashing membrane. (2) The technique of taping joints between insulation boards.

The surface upon which the roofing membrane is placed - structural deck or insulation.

The top-most layer of the roof system designed to protect the system from damage.

To remove a roof system down to the structural substrate.

A bar, usually metal or vinyl, used to seal and anchor the free edges of a roof membrane.

The stress producing phenomenon resulting from sudden temperature changes in a roof membrane, when for example, a rain shower follows brilliant sunshine.

A material that extends through a wall and is used to direct water entering a wall cavity to the exterior of the structure.

The joining of two different roof systems. Also a "tie-off".

A watertight seal used to terminate roof membranes at system adjuncts, terminations, flashings, or substrates. Can be temporary (Such as Night Seal) or permanent.

A material installed over the roof deck prior to the application of the primary roof coating. Usually consist of fifteen or thirty pound organic felt but can also be self-adhering such as an ice and water protection membrane.