Roofing Glossary

A

ACRYLIC COATING
A coating system with an acrylic resin base.
ADHERE
The bonding of one surface to another.
ADHESION
The state of adhering.
ALLIGATORING
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.
ALUMINIZED STEEL
Sheet steel with a thin aluminum coating on the surface to enhance the corrosion resistance.
ALUMINUM
A non-ferrous metal used in roofing and fabrication of gutters and flashings. It is highly resistant to corrosion and lightweight.
ASBESTOS
An incombustible fibrous mineral form of magnesium silicate formerly used for fireproofing and sometimes used for the reinforcement of roofing materials.
ASPHALT
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.)
ASPHALT FELT
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..

B

BASE FLASHING
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.
BASE SHEET
A saturated and coated felt placed as the first ply in a multi-ply built-up roofing membrane.
BITUMEN
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.
BLISTER
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.
BUILT-UP ROOFING MEMBRANE
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.
BUR
Abbreviation sometimes used for built-up roofing membranes.

C

CANT STRIP
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.
CAP SHEET
A mineral-surfaced coated felt used as the top ply of a built-up roofing system.
CAULK
The act of sealing a joint between two surfaces with an elastomeric compound.
COAL-TAR BITUMEN
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.
COAL-TAR PITCH
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.
COLD-PROCESS ROOFING
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.
CONDUCTER HEAD
A box-shaped sheet metal component used to direct water from a through-wall scupper to a downspout. Also known as a Collector Head.
COPING
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.
CRICKET
A roof component used to divert water away from curbs, platforms, chimneys, walls, or other roof penetrations and projections.
CURB
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.

D

DELAMINATION
A built-up roofing membrane failure characterized by separation of the felt plies, sometimes resulting in wrinkling and cracking.
DOWNSPOUT
A conduit for carrying water from a gutter, scupper, drop outlet or other drainage unit from roof to ground level.
DRAIN
A device used to carry water off a roof.

E

ELASTOMERIC
Having elastic properties, capable of expanding or contracting with the surfaces to which the material is applied without rupturing.
EPDM
Ethylene Propylene Diene Monomer, a rubber compound used to produce roof membranes and many other products.
EXPANSION JOINT
A provision in design intended to allow movement to occur within a structure at a predetermined location.

F

FASCIA
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.
FASTENERS
Devices used to secure roof system components.