Term Definition
Algae discoloration

A type of roof discoloration caused by algae. Commonly called fungus growth.


A bituminous waterproofing agent applied to roofing materials during manufacturing

Asphalt plastic roofing cement

An asphalt-based cement used to bond roofing materials. Also known as flashing cement or mastic; should conform to ASTM D-4586.


American Society for Testing and Materials. A voluntary organization concerned with development of consensus standards, testing procedures and specifications.

Back Surfacing

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

Balanced system

A ventilation system where 50% of the required ventilating area is provided by vents located in the upper portion of the roof with the balance provided by undereave or soffit vents.

Base flashing

That portion of the flashing attached to or resting on the deck to direct the flow of water onto the roof covering. Blisters:Bubbles that may appear on the surface of asphalt roofing after installation.

Built-up roof

A flat or low-sloped roof consisting of multiple layers of asphalt and ply sheets.


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

Butt edge

The lower edge of the shingle tabs.


See Asphalt plastic roofing cement.

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-resistance rating for roofing as per ASTM E-108. Indicates roofing is able to withstand severe exposure to fire originating from sources outside the building.

Class “B”

Fire-resistance rating that indicates roofing materials are able to withstand moderate exposure to fire originating from sources outside the building.

Class “C”

Fire-resistance rating that indicates roofing materials are able to withstand light exposure to fire originating from sources outside the building.

Closed cut 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 two inches 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 called a vent sleeve.

Concealed nail method

Application of roll roofing in which all nails are driven into the underlying course of roofing and covered by a cemented, overlapping course. Nails are not exposed to the weather.


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


The open portions of a strip shingle between the tabs.


An adjustable plate for controlling draft.


The surface installed over the supporting framing members to which the roofing is applied.


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

Double coverage

Application of asphalt roofing such that the lapped portion is at least two inches wider than the exposed portion, resulting in two layers of roofing material over the deck.


A pipe for draining water from roof gutters. Also called a leader.

Drip edge

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


The horizontal, lower edge of a sloped roof.

Eaves flashing

Additional layer of roofing material applied at the eaves to help prevent damage from water back-up.

Edging strips

Boards nailed along eaves and rakes after cutting back existing wood shingles to provide secure edges for reroofing with asphalt shingles.

Exposed nail method

Application of roll roofing in which all nails are driven into the cemented, overlapping course of roofing. Nails are exposed to the weather.

Exposure I grade plywood

Type of plywood approved by the American Plywood Association for exterior use.

Feathering strips

Tapered wood filler strips placed along the butts of old wood shingles to create a level surface when reroofing over existing wood shingle roofs. Also called horsefeathers.


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.


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. Galvanized metal flashing should be minimum 26-gauge.

Flashing Cement

See asphalt plastic roofing cement.

Free-tab shingles

Shingles that do not contain factory-applied strips or spots of self-sealing adhesive.


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. Contains a gable at each end.

Gambrel roof

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. Contains a gable at each end.

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. Contains no gables.

Masonry primer

An asphalt-based primer used to prepare masonry surfaces for bonding with other asphalt products.


See asphalt plastic roofing cement.

Mineral stabilizers

Finely ground limestone, slate, traprock or other inert materials added to asphalt coatings for durability and increased resistance to fire and weathering.

Mineral-surfaced roofing

Asphalt shingles and roll roofing that are covered with granules.

Natural ventilation

A ventilation system utilizing ventilators installed in openings in the attic and properly positioned to take advantage of natural air flow to draw hot summer or moist winter air out and replace it with fresh outside air.


A method of reroofing with new asphalt shingles over old shingles in which the top edge of the new shingle is butted against the bottom edge of the existing shingle tab.

Net free area

Area unobstructed by screens, louvers or other materials.

No-cutout shingles

Shingles consisting of a single, solid tab with no cutouts.

Non-veneer panel

Any wood based panel that does not contain veneer and carries an APA span rating, such as wafer board or oriented strand board.

Normal slope application

Method of installing asphalt shingles on roof slopes between 4 inches and 21 inches per foot.

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.

Organic felt

An asphalt roofing base material manufactured from cellulose fibers.


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


Wooden platforms used for storing and shipping bundles of shingles.