There is more to roofing than just shingles. Below are some of the most common technical terms used in our roofing industry. Hopefully this glossary of terms will be of some help.

Algae Discoloration

A type of roof discoloration caused by algae, normally shows as black streaks on the shingles.

Algae-Resistant Shingle

A shingle which has either copper or zinc granules embedded onto it, to inhibit the growth of algae.


A term used to describe the cracking of surfacing bitumen on a built-up roof. These cracks are the result of the limited tolerance of asphalt to thermal expansion or contraction, and produce a pattern that resembles an alligator's hide.

Asphalt Shingle

A shingle manufactured by coating a reinforcing material (felt or fibrous glass mat) with asphalt and having mineral granules on the side exposed to the weather.


The open area above the ceiling and under the roof deck of a steep-sloped roof.

Back Surfacing

Fine mineral matter applied to the back side of shingles to keep them from sticking.

Base Flashing

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


A package of shingles. There are 3, 4 or 5 bundles per square.

Butt Edge

The lower edge of the shingle tabs.


To fill a joint with mastic or asphalt cement to prevent leaks or a material to fill voids.

CDX Plywood

Grade of plywood approved by the American Plywood Association for exterior use; most common roof decking material.

Closed Valley

A method of valley treatment in which shingles from one side of the valley extend across the valley while shingles from the other side are trimmed approximately one inch from the valley centerline. The valley flashing is not exposed.


A layer of viscous asphalt applied to the base material into which granules or other surfacing is embedded.


Pre-formed flange placed over a vent pipe to seal the roof around the vent pipe opening (also known as a vent sleeve).


The change of water from vapor to liquid when warm, moisture-laden air comes in contact with a cold surface.

Counter Flashing

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


A row of shingles or roll roofing running the length of the roof.


Amount of weather protection provided by the roofing material. Depends on number of layers of material between the exposed surface of the roofing and the deck; i.e., single coverage, double coverage, etc.


A wood-framed structure that diverts water away from chimneys, walls or other vertical roof projections and penetrations (also known as a saddle).

Dimensional Shingle

A shingle that is textured, overlaid, or laminated and designed to produce a three-dimensional effect (also known as architectural shingle).


A framed window unit that projects through the sloping plane of a roof.


A pipe for draining water from roof gutters (also known as a leader).

Drip Edge

A piece of metal normally made of aluminum or steel used along the eaves and rakes to facilitate water run-off to drip clear of underlying construction.


A roof edge that extends past the exterior wall line of the building.


A deposit or encrustation of soluble salts, generally white and most commonly consisting of calcium sulfate, which may form on the surface of stone brick, concrete or mortar when moisture moves through and evaporates on the masonry.

Elastomeric Coating

A material which is applied over specific flat roofing materials to help extend the life of the flat roofing material by reducing heat build-up and surface cracking. This material, depending on the application, can be considered a complete roofing system.


Portion of the shingle exposed to the weather. Exposure is measured from the butt of one shingle to the butt of the next.


Horizontal trim board located at the eaves that cover the rafter ends. The trim located directly behind the gutter.


A flexible sheet of interwoven fibers saturated with asphalt and used as a protective underlayment between the shingles and the roof deck (also known as tar paper).


Metal or other flexible material used to seal the roof and prevent leaks around any projection in a roof such as vent pipes, chimneys, adjoining walls, dormers and valleys.

Flat Roof

A roof with a pitch less than two feet of rise over a twelve foot run.


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

Gable Roof

A type of roof containing sloping planes of the same pitch on each side of the ridge. A gable roof typically contains a gable at each end.


A type of roof containing two sloping planes of different pitch on each side of the ridge. The lower plane has a steeper slope than the upper. A gambrel roof usually contains a gable at each end, just like a standard gable roof.


Ceramic-coated colored crushed rock that is applied to the exposed surface of asphalt roofing products.


A trough along the eaves to catch, collect and move rainwater to a downspout.


The inclined external angle formed by the intersection of two sloping roof planes.

Hip Roof

A type of roof containing sloping planes of the same pitch on each of the four sides. A hip roof contains no gables.

Hip Shingles

Shingles used to cover the inclined external angle formed by the intersection of two sloping roof planes.

Ice Dam

Ice dams occur when snow melts and the water runs down the roof to the overhang, it cools and freezes. If the snow continues this melt and freeze process, an ice dam can form that can seep under the shingles, through the decking and into the house.

Ice-and-Water Shield

An underlayment material designed to protect against water infiltration caused by wind-driven rain and ice dams.

Laminated Shingles

Strip shingles containing more than one layer of tabs to create extra thickness (also known as three-dimensional shingles).


To cover the surface of one shingle or roll with another.


1"x2"x4' wood strips nailed to the roof, upon which the shingles or shake roofing material is attached to (also known as batten strips).

Lean-To Roof

A roof with one slope only that is built against a higher wall.


A continuous metal flashing installed along horizontal walls, bent to resemble an L.

Low-Slope Application

Method of installing asphalt shingles on roof slopes between a slope of two feet of rise over a twelve foot run (2/12) and four feet of rise over a twelve foot run (4/12).

Mansard Roof

A type of roof containing two sloping planes of different pitch on each of four sides. The lower plane has a much steeper pitch than the upper, often approaching vertical. Has no gable.


An asphalt-based cement/-caulk used to bond roofing materials (also known as flashing cement).

Modified Bitumen

Rolled roofing membrane composed of a composite sheet consisting of copolymer modified asphalt, often reinforced with polyester and/-or fiberglass. Mostly used on flat roofs, this material usually has multiple application methods.

Open Valley

Method of valley construction in 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.


The portion of the roof structure that extends beyond the exterior walls of a building.


A low protective wall that extends above the roofline or balcony for support.


A fine film developing on copper by natural oxidation and often valued for its ornamental quality; usually a brownish color which eventually becomes a greenish color.


Pitch is the measure of how "steep" a roof is. For example, if a roof is "4 in 12", the roof rises 4 inches for every horizontal run of 12 inches; also called slope.


The supporting framing member immediately beneath the roof deck, sloping from the ridge to the wall plate.


The inclined edge of a sloped roof over a wall from the eave to the ridge.


A groove cut into masonry with a diamond blade for the attachment of counter flashing.


The uppermost, horizontal external angle formed by the intersection of two sloping roof planes; also called roof peak.

Ridge Shingles

Shingles used to cover the horizontal external angle formed by the intersection of two sloping roof planes.

Ridge Vent

A type of roof exhaust vent that ventilates the attic along the ridge of the roof; works best with soffit vents under the eaves.


The vertical distance from the eaves line to the ridge.

Roof Deck

The substrate over supportive framing (rafters) to which roofing material is applied (also known as decking or sheathing). Most new homes have decking made of plywood.


The horizontal distance from the eaves to a point directly under the ridge.

Self-Sealing Shingles

Shingles containing factory-applied strips or spots of thermal sealant to firmly adhere the shingles together after they have been installed and exposed to warm sun temperatures. In warm seasons, the seal will be complete in a matter of days.


Slight differences in shingle color that may occur as a result of normal manufacturing operations.


Exterior grade boards used as a roof deck material. "Step sheathing" is used alone or in combinations with solid sheathing for installation of tiles or shakes.

Shed Roof

A roof containing only one sloping plane, with no hips, ridges, valleys or gables.


The degree of roof incline expressed as the ratio of the rise, in inches, to the run, in feet.


The underside of the eaves or roof overhang, which can be enclosed or exposed.

Soffit Vent

An intake vent in the soffit area that provides attic venting at the lower portion of the roof deck; works best in conjunction with attic exhaust ventilation such as ridge vents.


A combination of tin and lead used for joining or patching copper.


The horizontal distance from eaves to eaves.


A unit of roof measure covering 100 square feet.

Steep-Slope Application

Method of installing asphalt shingles on roof slopes greater than 21 inches per foot.

Step Flashing

Flashing application method used where a vertical surface meets a sloping roof plane.

Strip Shingles

See "Three-tab shingle"


The exposed portion of strip shingles defined by cutouts.

Tar Paper

See "Felt"

Tear Off

Removing an existing roof system.


A shingle distortion that may arise when a new roof is applied over an uneven surface.

Three-Dimensional Shingle

See "Laminated shingle”

Three-Tab shingle

The most popular type of asphalt shingle, usually 12" x 36" in size with three tabs.

Top Lap

The portion of the roofing covered by the succeeding course after installation.


Underwriters Laboratories, Inc.

UL Label

Label displayed on packaging to indicate the level of fire and/or wind resistance of asphalt roofing.


A roofing material installed directly to a roof deck beneath the roofing material; also called felt, tar paper and ice-and-water shield.


The internal angle formed by the intersection of two sloping roof planes to provide water runoff.


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

Vent Pipe

Pipes that vent the drainage system from sinks, bathtubs, showers and toilets; part of the plumbing system.


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Dunbar Roofing & Siding Co.

601 Berwyn Ave

Berwyn, PA 19312