Roofing Terms & Definitions

Asphalt Emulsion:
Surface coating for some cold applied roof systems. Used as a base for smooth applied systems. Can be spray applied or brushed on.

Base Sheet:
First layer of paper applied usually 3 times thicker than ply sheets and coated.

Built Up Roofing:
A method of applying a roof system composed of various amounts of roofing paper (base sheet and ply sheets) to achieve a waterproof membrane. Can be hot applied or cold applied.

Cap Sheet:
Surface sheet for most built up roof systems. Can be made of organic asphalt products or modified asphalt products.

Chopped Fiberglass:
A method of reinforcing asphalt emulsion allowing application of a larger amount of asphalt emulsion thus preventing material from cracking. Material is applied with a special spray gun.

Coated Sheet:
Has an asphalt and sand finish. The finish keeps the asphalt or adhesive from seeping through sheet.

Cold Application Material:
Solvent based material used for applying built up roof system. Can be spray applied or brushed on.

Granule Surfacing:
A small granule product manufactured for roof surfacing. Size would be comparable to rock salt.

Gravel Surface:
Gravel used for surfacing built up roofing.

Hot:
Hot asphalt that is used for bonding ply sheets and surface coatings and or cap sheets. It is melted on job site by kettles or tankers.

Kettle:
A large butane fired trailer that melts the asphalt on the job site, sometimes referred to as a tar pot.

Mechanical Fasteners:
Roofing Nails, special screws and plates are used to fasten roof insulation and single ply membranes. Can be metal or plastic.

Modified:
Cap sheet or ply sheets that are manufactured with a modified rubber product. More tensile strength than regular asphalt products.

Ply:
Roofing sheets used in built up roofing systems, also referred to as "felt." Can be made of organic asphalt products or modified asphalt products.

Polyester Membrane:
Reinforcing membrane sheet used in the cold overlay system.

Roof Insulation:
A rigid board of various widths from ½"to 6", usually applied with some form of mechanical fasteners. When more than one layer is applied the second layer will applied with an adhesive, either hot or cold.

Single Ply Roofing:
A rubber roof membrane that is applied with or without adhesive and is sealed and fastened at the laps of the material. Laps are sealed with heat welding using special hot air welders or special lap adhesive. Heat welding is the preferred method of sealing laps.

Tanker:
Vehicle that transports cold asphalt or hot asphalt to job site.

Tear off:
Removal of existing roof membrane, necessary when applying new roof membrane in most cities in Southern California.

Torch Applied System:
The cap sheet has a coating of modified asphalt that is heated with torch just prior to application.