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Common Roofing Materials

Frequently Asked Questions

Getting Up on Roofs: Tips From the Experts

Glossary of Common Roofing Terms

A - C

D - L

M - R

S - Z

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Glossary of Common Roofing Terms

A - C

D - L

M - R

S - Z



Saddle: A small, somewhat pyramid-shaped structure erected in between roof drains that is used to direct run-off water toward the drains.

SBS: See Styrene Butadiene Styrene.

Sealant: A generic term for a multitude of materials used to seal joints or junctures against moisture or weather.

Seam: A line, ridge, or groove formed from fitting, joining or lapping two sections together.

Self-Adhering Membrane: A type of membrane whose bottom surface will stick or adhere to a substrate without the use of an additional adhesive material.

Self-Sealing Shingle: Asphalt shingles with adhesive strips on the back that will soften and stick to the following course of shingles when heated by the sun. Self-sealing helps to increase resistance to wind uplift.

Shed Roof: A roof with only one sloping plane. Also known as Half Gable.

Shingle: A single piece of prepared roofing material, either asphalt or wood, for use in steep slope roof systems.

Side Lap: The longitudinal overlap of neighboring materials.

Single-Ply Membranes: Roofing membranes that are applied in one layer. Seams of single-ply membranes can be heat welded, solvent welded or and adhered using seam tape or other adhesives.

Slate: A fine-grained metamorphic rock that splits into thin, smooth-surfaced layers used in steep slope roofing applications.

Slope: The angle of incline of a roof expressed as a percentage or as a ratio of rise to run. See Roof Slope.

Smooth Surfaced Roof: A roof with no surfacing or with a smooth surfacing such as emulsion or a reflective coating.

Soffit: The underside of a roof overhang.

Soffit Vent: An intake ventilation device located in the soffit.

Softening Point: The temperature at which bitumen will begin to flow.

Solar Reflectance: A measure, expressed as a number between 0 (low) and 1 (high) of the ability of a material to reflect sunlight, including visible, infrared and ultraviolet wavelengths.

Solid Mopping: To continuously apply hot asphalt or coal tar, leaving no areas without bitumen.

Solvent: A liquid capable of dissolving other substances, such as bitumen.

Solvent Weld: To weld materials using a liquid solvent.

Split: The separation of a material resulting from tensile forces.

Sprayed Polyurethane Foam (SPF): A monolithic sprayed-on roofing material with a high R-value, which is formed when isocyanate ("A" component) and resin ("B" component) are mixed.

Sprinkle Mopping: To scatter hot bitumen over a surface.

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

Spud Bar: A long-handle tool with a stiff flat blade on one end (usually 4" or 6" wide) that is used to scrape and remove the top surfacing of a roof down to the membrane.

Square: 100 square feet of roof area.

Standing Seam: 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.

Starter Course: The primary course of roofing material. The starter course is installed along the downslope perimeter edge and usually covered by the first course of roofing.

Starter Plies: Felt or ply sheets that are cut into widths that are proportionate to the reciprocal of the number of plies being installed. For instance, with a three-ply built-up roof, the first starter ply would be one-third of the roll width, the second two-thirds of the roll width installed over it, and then a full ply over those.

Steep Asphalt: A roofing asphalt that can be used on roofs with slopes up to 3 in 12 (25%).

Steep-Slope Roof: A roof with a slope greater than or equal to 3 in 12 (25%).

Steep-Slope Roofing Materials: Roofing materials (such as asphalt shingles, wood shakes, tile and slate) that depend on their water-shedding capabilities to keep moisture from entering a building. These materials are generally installed on roofs with slopes that equal to or exceeding 3 in 12 (25%).

Step Flashing: Pieces of metal or other material that are used to flash roof projections such as chimneys, walls, curbs, etc. The pieces are installed between each course of roofing and generally have a vertical flange equal in length to that of the horizontal flange.

Styrene Butadiene Styrene (SBS): The polymer that is added to SBS modified bitumen roofing that gives the material a rubber like quality.

Substrate: The surface that the roof is installed upon.

Surfacing: The top-most layer of the roof system.


Tar Boil: A small bubble found in the flood coat of an aggregate-surfaced built-up roof that is usually the result of trapped moisture vapor. Tar Boils are also known as blueberries.

Tear-Off: To remove a roof system down to the substrate.

Termination: The sealed edges of a roof membrane.

Termination Bar: A bar, usually made of metal or vinyl, that is used to seal and anchor the free edges of a roof membrane.

Thermal Emittance: A measure, expressed as a number between 0 (low) and 1 (high), of the ability of a material to release absorbed heat.

Thermal Insulation: A material used to reduce heat flow into and out of a building.

Thermal Movement: Expansion and contraction of a roofing material resulting from temperature changes.

Thermal Resistance (R): The measure of a material’s ability to resist heat flow. The higher a material’s R-value, the better it insulates.

Thermoplastic: A type of roofing membrane material that can be repeatedly softened by heating and hardened by cooling. Thermoplastic membranes are typically seamed by heat welding with hot air or solvents. Polyvinyl chloride (PVC) and Thermoplastic Olefin (TPO) are the most common thermoplastic roof membranes.

Thermoset: Unlike a thermoplastic membrane material, a thermoset membrane material incorporates polymers that are chemically cross-linked or vulcanized. Once they “set”, they cannot be re-softened or re-shaped by heating. They can only be bonded to similar materials with adhesives. Ethylene Propylene Diene Monomer (EPDM) is the most common thermoset roof membrane.

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

Tie-In: The joining of two different roof systems.

Tie-Off: A watertight seal used to terminate roof membranes at system adjuncts, terminations, flashings or substrates.

Title 24: That part of the California Code of Regulations that sets forth the State’s building standards (electrical, fire, general building, mechanical, plumbing, etc.), as well as the California Energy Code. Among California roofing contractors, use of the term “Title 24” is usually shorthand for the Cool Roofing requirements contained in the Energy Code.

Traffic: Any rooftop activity that can potentially damage the roof surface.


Underlayment: A material installed over the roof deck prior to the application of the primary roof covering. Underlayment usually consists of fifteen- or thirty-pound felt, but ice and water protection membrane can also be used for this purpose.

Underwriters Laboratories (UL): A non-profit agency which functions as the testing arm of the National Board of Fire Underwriters. UL maintains laboratories for the examination and testing of various devices, systems, and materials to determine their safety against the hazards of fire, wind, and accidents.

Uplift: See Wind Uplift.

Upside Down Roof: See Protected Membrane Roof.


Valley: The internal intersection of two sloping roof planes that runs from the eaves to the ridge. This intersection collects the most water run-off.

Vapor Retarder: A material used to restrict the passage of water vapor through a roof assembly.

Viscosity: The resistance of a material to heat flow.

Viscous: Having a fairly high resistance to heat flow.

Void: An open space or a break in continuity; a gap.


Waterproofing: The treatment of a surface or structure in order to prevent the passage of water under hydrostatic pressure.

Weather: To undergo degradation in quality and appearance due to exposure to the sun, wind, rain, etc.

Weep Holes: Small holes used to permit moisture that has gathered inside a building component to drain.

Wick: To convey liquid by capillary action.

Wind Clip: A clip that slips over the ends of tile, slate and other steep slope roofing materials in order to help secure them and resist wind uplift.

Wind Load: The force that wind puts on structures.

Wind Uplift: The upward displacement of a roof system or section thereof caused by the movement of air across the surface of a roof.

Wire Tie: A system for attaching heavy steep slope roofing materials, such as slate or tile, by using wire fasteners in addition to or in place of nails.

Woven Valley: A valley construction whereby the valley has a woven look, which is achieved by overlapping alternate courses of shingles from both sides of the valley.


Z- or Z-Section: A piece of steel formed in the shape of a "Z."

Zinc: A bluish-white, lustrous metallic element that is brittle at room temperature but malleable when heated. In roofing, zinc is a common component of a variety of alloys used to make gutters, flashings and edge metals. 

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