Glossary of Terms

roof_diagram Roof-Types-Diagram2

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.

Cap Flashing – That portion of the flashing attached to a vertical surface to prevent water from migrating behind the base flashing.

Caulk – To fill a joint with mastic or asphalt cement to prevent leaks.

Chalk Line – A line made on the roof by snapping a taut string or cord dusted with chalk.  Used for alignment purposes.

Class “A”– The highest fire-resistant rating issued by Underwriters Laboratories (UL) for roofing.  Indicates roofing is able to withstand severe exposure to fire originating from sources outside the building.

Class “B”– Rated to withstand moderate exposure to fire.

Class “C”– Rated to withstand light exposure to fire.

Class 4 – The highest impact resistant shingle.

Coating – A layer of viscous asphalt applied to the base material into which granules are embedded.

Counter Flashing – SEE CAP FLASHING

Cricket – A peaked saddle construction at the back of a chimney to prevent accumulation of snow and ice and to deflect water around the chimney.

Collar – Pre-formed flange placed over a vent pipe opening. Also called a vent sleeve.

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.