Pacific Weathershield Roofing - Providing Comprehensive Roofing Solutions - Bay Area, California

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Glossary of Roofing Terms

(1) Crushed stone, crushed slag or water-worn gravel used for surfacing a built-up roof.  (2)  Any granular mineral material.

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 roof membrane.         

A dark brown to black cementitious material in which the predominating components are bitumens, which occur in nature or are obtained in petroleum processing.

Asphalt Felt: 
An asphalt-saturated felt or an asphalt-coated felt.

Asphaltic Clay Emulsion:
An asphalt emulsion using bentonite clay as a base.                     

The practice of blind nailing all the plies of a substrate to prevent slippage.

Base Flashing:
An upturned flashing area typically at the base of the parapet wall, skylight, A/C unit, or other projection that has vertical roofing.

Base Sheet:
A saturated or coated felt placed as the first ply in some multi-ply built-up roof membranes.                           

The generic term for an amorphous, semi-solid mixture of complex hydrocarbons derived from any organic source.  Asphalt and coal tar are the two bitumen’s used in the roofing industry.

Containing or treated with bitumen.  Examples: bituminous concrete, bituminous felts and fabrics.

A spongy raised portion of a roof membrane, ranging in area from 1 in. in diameter and of barely detectable height upward.  Blisters result from the pressure build up of gases entrapped in the membrane system.  These gases most commonly are air and/or water vapor.  Blisters are usually delamination of the underlying membrane plies.

Built-up Roof Membrane:                
A roof membrane assembly, consisting of plies of saturated felts, coated felts, fabrics or mats between which alternate layers of bitumen are applied, generally surfaced with mineral aggregate, bituminous materials or a granule-surfaced roofing sheet. (Abbreviation:  BUR)

Cant Strip: 
A beveled strip of wood or wood fiber that fits into the angle formed by the intersection of a horizontal surface and a vertical surface.  The 45-degree slope of the exposed surface of the cant strip provides a gradual angular transition from the horizontal surface to the vertical surface.

Cap Sheet: 
A granule-surfaced coated sheet used as the top ply of a built-up roof membrane or flashing.

Coated Base Sheet:
A felt that has been impregnated and saturated with asphalt and then on both sides with harder, more viscous asphalt to increase its impermeability to moisture.

Cold Process Roofing:
A continuous, semi-flexible roof membrane, consisting of plies of felts, mats or fabrics that are laminated on a roof with alternate layers of cold-applied roof cement and surfaced with a cold-applied coating.

The covering piece placed on top of a parapet wall that is exposed to the weather.  It is usually sloped to shed water, and constructed from sheet metal.

Formed metal or elastomeric sheeting secured on or into a wall, curb, pipe, rooftop unit or other surface to cover and protect the upper edge of a base flashing and its associated fasteners.

A superimposed construction placed in a roof area to assist drainage, usually triangular or diamond shaped.

Treatment of a surface or structure to resist the passage of water.

Josam Type Drain:
A cast iron type roof drain with a debris cover.

The term used to describe the elastic, rubber-like properties of a material.

(1) The process of pressing a felt, aggregate, fabric, mat, or panel uniformly and completely into hot bitumen or adhesive. (2) The process of placing a material into another material so that it becomes an integral part of the whole material.

Expansion Joint:
A structural separation between two building elements designed to minimize the effect of the stresses and movements of a building’s components and to prevent these stresses from splitting or ridging the roof membrane.

(1) The transverse dimension of a roofing element not over-lapped by an adjacent element in any roof system. The exposure of any ply in a membrane may be computed by dividing the felt width minus 2 inches by the number of shingle plies; thus, the exposure of a 36-inch-wide felt in a shingled, four-ply membrane should be 8-1/2 inches. (2) The time during which a portion of a roofing element is exposed to the weather.

Fiberglass Fabric:
A woven cloth of vinyl coated fiberglass used as reinforcement.

A half-cylindrical or half-conical opening formed by an edge wrinkle. Something good to hook into on a Saturday morning.

The system 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 counterflashing shields the upper edges of the base flashing.

Flashing Cement:
A trowelable mixture of cutback bitumen and mineral stabilizers. Flashing cement is used on vertical surfaces.

Flood Coat:
The top layer of bitumen into which the aggregate is embedded on an aggregate-surfaced built-up roof.

Glass Fiber Felt:
A felt sheet in which glass fibers are bonded into the felt sheet with resin. Glass fiber felts are suitable for impregnation and coating. They are used in the manufacture and coating of bituminous waterproofing materials, roof membranes, and shingles.

Gravel Stop:
A flanged device, frequently metallic, designed to provide a continuous finished edge for roofing materials and to prevent loose aggregate from washing off the roof.

Mineral Surfaced Roofing:
Built-up roofing materials whose top ply consists of a granule-surfaced sheet. A felt that is coated on one side with asphalt and surfaced with mineral granules.

Mole Run:
A meandering ridge in a roof membrane not associated with insulation or deck joints.

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

Picture Framing: 
A rectangular pattern of ridges in a roof membrane over insulation or deck joints.

Pitch Pocket: 
A flanged, open bottom, metal container placed around columns or other roof penetrations that is filled with grout and elastomeric flashing compound.

Plastic Roofing Cement: 
A trowel grade asphalt cutback, used as a roof repair material (mastic).

A groove in a wall or other surface adjoining a roof surface for use in the attachment of counterflashing.

Shark Fin:
An upward-curled felt side lap or end lap.

A separation in roofing material resulting from movement of the substrate.

Surface Mounted Counterflashing:
A metal counterflashing mounted to the surface of a wall.

Through-Wall Scupper: 
A sheet metal drain that protrudes through a wall.

Three Coursing:
Roof repair method using plastic roof cement or flashing compound and embedding vinyl coated fiberglass fabric.

Thermal Shock:
The stress-producing phenomenon resulting from sudden temperature changes in a roof membrane. (For example, when a rain shower follows brilliant sunshine or spring and fall when nighttime temperatures are very cold and daytime temperatures are very warm.)

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.