Glossary of terms


Aggregate – Crushed stone, crushed slag or water worn gravel used for surfacing a built-up roof.

Alligatoring – 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 surfacing bitumen.  Alligatoring is not always indicative of roof failure or leakage.

Algae Discoloration – A type of roof discoloration caused by algae.  Commonly called fungus growth.  Many manufactures produce algae resistant shingles.  Look for “AR”.

Aluminum paint – An oil based coating mixed with aluminum particles, used for protecting asphalt roofs from UV rays & preserving a roofs life.

Asphalt – A black bitumen material used in roofing in hot or cold form, also called tar.

Asphalt Felt – An asphalt-saturated felt or an asphalt coated felt, primarily used as the base layer on sloped roofs.  A form of under lament and can come in #15 & #30.  #30 being the thicker of the two.

Asphalt Plastic Cement – An asphalt-based cement used to bond roofing materials.  Also known as flashing cement or mastic.


Base Flashing – That portion of flashing attached to or resting on the deck to direct the flow of water onto the roof covering.

Built-up Roof– A flat or low pitched roof consisting multiple layers of asphalt and ply sheets.

Bundle(s) – A package of shingles.  There a generally 3 bundles to a square but can be 4 or 5 depending on weight.  Ex. GAF/ELK 50 year is 5 Bundles per square.


Deck – The surface, installed over the supporting framing members, to which the roof is applied.

Dormer – A framed window unit projecting through the sloping plane of a roof.

Downspout – A pipe for draining water from the roof gutters.

Drip Edge – A non-corrosive, non-staining material used along the eaves and rakes, flush with the fascia, to allow water run-off to drip clear of underlying construction.

Drying-In – The application of roofing felt to the rook deck.


Eaves – The horizontal, lower edge of a sloped roof.

Elastomeric – A rubber like synthetic polymer that will stretch when pulled and will return quickly to its original shape when released, primarily used for waterproofing walls and vertical surfaces.


Fascia – The wood trim covering the rafters and rafter ends, just beneath the drip edge.  Located at the end of the eaves and rakes.

Felt – Fibrous material saturated with asphalt and used as an underlayment or sheathing paper.

Fiber Glass Mat – An asphalt roofing base material manufactured from glass fibers.

Flashing – Pieces of metal or roll roofing used to prevent seepage of water into a building around any intersection or projection in a roof such as vent pipes, chimneys, adjoining walls, dormers and valleys.

Flashing Cement – See Asphalt plastic cement.


Gable – The upper portion of a sidewall that corners to a triangular point at the ridge of a sloping roof.

Gable Roof – The upper portion of a sidewall that comes to a triangular point at the ridge of a sloping roof.

Galvanize – To plate with zinc, originally by shock galvanic action, providing protection from rust.

Granules – Ceramic, color-coated crushed rock that is applied to the exposed surface of asphalt roofing products.

Gutter – The trough that channels water from the eaves to the downspouts.


Hip – The inclined external angle formed by the intersection of two sloping roof planes.  Runs from the ridge to the eaves.

Hip Roof – A type of roof containing sloping planes of the same pitch on each of four sides.  Contains no gables.


Laminated Shingles – Strip shingles containing more than one layer of tabs to create extra thickness.  Also called three-dimensional shingles.

Lead Pipe Jacks – A lead flashing installed over the PVC pipes that extend out through roof.

Low Slopes – Roof pitches less than a 4/12 pitch are considered low sloped roofs.  Special installation practices must be used on roofs sloped 2/12-4/12.


Mansard Roof – A type of roof containing two sloping planes of different pitch on each of four sides.  The lower plane has I much steeper pitch than the upper, often approaching vertical.  Contains no gables.

Mastic – See asphalt plastic cement.

Membrane – A flexible or semi-flexible roof covering or waterproofing layer, whose primary function is the exclusion of water.

Modified Bitumen – Rolled roofing membrane with polymer modified asphalt and either polyester or fiberglass reinforcement.


Ninety-Pound (#90) – A prepared organic felt roll roofing with a granule surfaced exposure that has a mass of approx. 90 LBS per Square/100 Square feet.

NRCA – The National Roofing Contractors Association.


OpenValley – Method of valley construction is which shingles on both sides of the valley are trimmed along a chalk line snapped on each side of the valley.  Shingles do not extend across the valley.  Valley flashing is exposed.

OSB – Oriented Strand Board.  A decking made from wood chips and lamination glues.

Overhang – That portion of the roof structure that extends beyond the exterior walls of a building.


Parapet Wall – The part of any wall entirely above the roof.

Pitch – The degree of roof incline expressed as the ration of the rise, in feet to the span, in feet.

Ply – The number of layers of roofing.  Generally applied to flat roofs, i.e. one-ply, two ply.

Power Vents – Electrically powered fans used to move air from attics and structures.  Installed through the decking.


Rafter – The supporting framing member immediately beneath the deck sloping from the ridge to the wall plate.

Rake – The inclined edge of a slope roof over a wall.

Ridge – The uppermost, horizontal external angle formed by the intersection of two sloping roof planes.

Ridge Shingles – Shingles used to cover the ridge.  Also called ridge cap.

Rise – The vertical distance from the eaves line to the ridge.

Roll Roofing – Asphalt roofing products manufactured in roll form.  Used on low to no sloped roofs.


Sheathing – Exterior grade plywood or tongue-and grove boards used as a roof deck.

Shed Roof – A roof containing only one sloping plane. Have no hips, ridges, valleys or gables.

Slope – The degree of roof incline expressed as the ration of the rise, in inches, in the run in feet.

Smooth-Surface Roofing – Roll roofing that is covered with ground talc or mica instead of granules.

Soffit – The finished underside of eaves.

Square – A unit of roof measure covering 100 square feet. A 10’ x 10’ section.

Starter Strip – Asphalt roofing applied at the eaves that provides protection by filling in the spaces under the cutouts and joints of the first course of shingles.


Three Tab Shingles – Flat asphalt roofing shingles.  20,25 & 30 year warranty.  The cheapest form of shingles.


Underlayment – A layer of material under the roofing and on top of the decking.  Mainly felt, #15 or #30.


Valley – The internal angle formed by the intersecting of two sloping roof planes.

Vent – Any outlet for air that protrudes through the roof deck such as a pipe of stack.  Any device installed on the roof, gable or soffit for the purpose of ventilating the underside of the roof deck/attic.

Roof Diagram

Roof Types