Our roofing glossary will help you understand the terms and phrases that you might hear in your roof replacement job.

Understanding Roofing Terminology

You may encounter industry terms used by your contractor when discussing your roofing project. You can ask your contractor to clarify any ambiguities, but it is helpful to have a reference guide.

Check out our glossary on roofing to learn more about the meanings of common residential roofing terms.

Algae Coloration: This is a type of roof discoloration that is caused by algae. Often mistakenly called fungus growth.

ARMA The Asphalt Roofing Manufacturers Association is a trade organization for North American asphalt roofing manufacturers.

ASTM International – A voluntary association that works to develop consensus standards, specifications and testing procedures.

Asphalt – A bituminous waterproofing product that is applied to roofing materials during manufacturing.

Asphalt Primer – A thin liquid bitumen that is applied to a surface in order to increase adhesion and absorb dust.

Asphalt Roof Cement is an asphalt-based cement that bonds roofing materials. Also called flashing cement, mastic, and should comply with ASTM D4586 (Asbestos-Free).

Architectural Shingles – See Laminated Shingles.

Back Surfacing – Fine mineral matter is applied to the back of shingles to prevent them from sticking together.

Base Flashing : This flashing is attached to the deck or resting on it to direct water flow onto the roof covering.

Base-ply Sheet: This product is intended to serve as the base or middle layer in a residential self adhesive roll roofing system.

Base Sheet – A product that is intended to be used in a self-adhering rolling roofing system as a base sheet.

Bubbles: After installation, bubbles may form on asphalt roofing.

Bridging – A method for repointing with metric-sized shingles.

Built up Roof: Flat or low-sloped roof made of multiple layers of ply sheets embedded into hot asphalt.

Bundle – A bundle of shingles. You will typically find 3, 4, or 5 bundles per square.

Butt edge : The lower edge between the shingle tabs. (See Figure A.

Figure A

Capsheet: A mineral-surfaced material that can be used as a single layer or as the top of a multi-layered rolled roof covering.

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

Cement – See Asphalt Roof Cement.

Chalk Line – A line created on the roof using a taut string, or cord dusted in chalk. This is used for alignment purposes.

Class A Fire Resistance: This is the highest fire classification for roofing according to ASTM E108 and UL790. This indicates that roofing can withstand extreme fire from outside sources.

Class B Fire Resistance: This classification indicates that roofing material can withstand moderate fire from outside sources.

Class C Fire Resistance: This classification indicates that roofing material can withstand light exposure from fires originating outside.

HTML4 Impact Resistance: This is the highest classification of impact resistance according to the UL 2218 Impact Test. It indicates that shingles are more resilient to impacts from hailstorms.

Closed Cut Valley – This is a method for treating the valley. Shingles from one side extend across the valley, while those from the opposite side are cut 2 inches from the valley centerline. Valley flashing is not visible.

Collar : A pre-formed flange that is placed over a ventpipe to seal the roof and vent pipe openings. Also known as a vent sleeve.

Concealed nail method: Roll roofing is where all nails are driven into roofing’s underlying course and then covered with a cemented, overlapping roof. The weather is not allowed to touch nails.

Condensation – The conversion of water from vapor into liquid when warm, moist air is in contact with cold surfaces.

Counter Flashing – This is the portion of the flashing that’s attached to a vertical surface in order to stop water from escaping behind the base flashing.

Course: A row or roll of roofing that runs the length of the roof.

Coverage – The number of layers between the roof and the deck.

Cricket: A saddle-shaped structure at the back of the chimney that prevents accumulation of snow or ice and deflects water around it.

Cutout : The open areas of a strip-shingle that are between the tabs. (See Figure A.

Deck – The top, which is installed on the supporting framing members to which the roofing will be applied. A wood deck must be at least 15/32 inches thick.

Dormer – A framed unit that projects through the sloped roof plane.

Double Coverage – Asphalt roofing that is more than 2 inches wider than the exposed part. This results in two layers of roofing material on the deck.

Downspout : A pipe that drains water from roof gutters. Also known as a leader.

Drip Edge – A non-staining, corrosion-resistant material that is used to cover rakes and eaves to allow water to run off the construction.

Edge: A horizontal, lower edge on a sloped roof. (See Figure B.

Eave Flashing : An additional layer of roofing material is applied to the eaves in order to prevent water damage.

Exposed nail Method: Roll roofing is where all nails are driven into the cemented roofing. The weather is not affected by nails.

Exposure – The area of the roof that is exposed to the elements after installation. (See Figure A.

Felt Fibrous material that has been saturated with asphalt. It is used underlayment or sheathing papers.

Fiberglass Mat – The core material of an asphalt roofing shingle made from glass fibers.

Flashing – Metal pieces used to stop water seepage from buildings around roof projections such as chimneys, vent pipes, chimneys and adjoining walls. Galvanized metal flashing should not exceed 26 gauge.

Flashing cement – See Asphalt Roof Cement.

Gable : The triangular upper portion of a sidewall reaching a point at a ridge of double-sloped roof. (See Figure B.

Gable Roof : A simple, two-sided roof that is above a Gable.

Gambrel Roof A roof that has two sloped planes with different pitches on either side of the ridge. The slope of the lower plane is steeper than that of its counterpart. Each end has a gable.

Granules – Typically, this is a colored crushed rock coated with ceramic that is used to cover asphalt roofing products.

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

Head Lay: The shortest distance between the butt edge and the top edge of an over-shaded shingle to reach the upper edge of the shingle in the course below. Triple coverage of the top lap made of strip shingles. (See Figure A.

Hexagonal Shingles – Shingles with the appearance of a hexagon following installation.

Hip – An inclined external angle created by two sloped roof planes. From the ridge to eaves. (See Figure B.

Hip Roof – A roof that has sloping planes at each of its four sides. Contains no gables.

Shingles – Shingles were used to cover an inclined external angle created by two sloped roof planes.

Ice Dam: A condition formed at the lower roof edge from the thawing of melted snow. Leakage can occur when ponded water is forced up and under the shingles.

Ice Dam Protection A course of self-adhering, underlayment placed at the eaves to protect against water damage caused by an ice dam. Also called “Eave Flashing”.

Shingles with Impact Resistance are Shingles that have been specifically designed to resist hailstorm impacts. UL 2218 defines the classification of impact resistant shingles. They can be classified as Class 1 to 4, with Class 4 being the most severe.

Interlocking Shingles : Individual shingles that mechanically attach to one another to provide wind resistance.

Laminate Shingles Shingles with more than one layer that add thickness. Also known as architectural shingles, three-dimensional shingles, or architectural shingles.

Lap : To cover one shingle with another.

Lap Cement is an asphalt-based cement that conforms to ASTM D3019. It’s used to attach overlapping rolls of roll roofing.

Low Slope Application – Method for installing asphalt shingles on roof slopes between 2″ and 4″.

Mansard Roof – A roof that has two sloped planes with different pitches on each side. The pitch of the lower plane is often steeper than that of its counterpart, and can even be considered vertical. (See Figure B.

Mastic – See Asphalt Roof Cement.

Midply Sheet – See base-ply sheet.

Mineral Stabilizers : Finely ground limestone and slate are added to asphalt shingles to increase durability and resistance to weathering and fire.

Mineral-Surfaced Roof: Roll roofing and asphalt shingles that have granules.

Nesting is a method to re-roof old asphalt shingles with new asphalt shingles. The top edge of new shingle is bounded against the bottom edge the existing shingle tab.

No-Cutout Shingles : Shingles made up of one solid tab without any cutouts.

Non-Veneer Panel – Any wood-based panel without a laminated veneer that carries an APA span rating such as wafer board, oriented strand board or wafer board.

Open Valley – This is a method of building a valley. Shingles are cut along a chalk line and placed on either side of the valley. Shingles are not extended across the valley. Valley flashing can be seen.

Organic felt is an asphalt roofing material made from cellulose fibers.

Overhang – The portion of the roof that extends beyond the building’s exterior walls.

Pallets – Wooden platforms for shipping and storing bundles of shingles.

Plly: A layer for roofing (i.e. one-ply or two-ply).

Ponding – The accumulation of water following rainfall on low-lying roof areas that remain wet after other roof parts have dried.

Primer – An asphalt-based primer that prepares surfaces for bonding with self adhesive asphalt sheets.

Racking – This is a method of roofing application in which shingle course are applied vertically to the roof.

Rafter : The supporting framing member directly beneath the deck, sloping downwards from the wall plate to the ridge.

Rake : An inclined edge of a roof that slopes over a wall. (See Figure B.

Random Tab Shingles : Shingles that vary in size or exposure.

Recovering: Adding an additional layer to a layer of roofing. Roofs can have up to two layers of any type of roofing.

Release Tape – A strip of plastic that is applied to the backs of self-sealing roofing shingles. This prevents shingles from sticking together and can be used for applications.

Re-roofing is the process of removing roof coverings and installing a new roofing system.

Ridge : The highest horizontal angle created by the intersection two sloped roof planes. (See Figure B.

Ridge Shingles : Shingles were used to cover horizontal angles formed by two sloped roof planes intersecting.

Rise: Vertical distance between the ridge and the eaves.

Roll roofing: Asphalt roofing products made in roll form.

Roofing Tape is an asphalt-saturated adhesive tape that’s used with asphalt cements to flashe and patch asphalt roofing.

Run: The horizontal distance between the eaves and a point under the ridge. Half of the span.

Saturated felt: A asphalt-impregnated felt that is used to underlay the roof and deck.

SBS: Styrene-Butadiene-Styrene, which is a synthetic polymer that is mixed with asphalt in some products to increase the flexibility and other attributes of the products.

Self-Adhering Shingle underlayment: This waterproofing underlayment is self-adhering and can protect from water infiltration caused by ice dams and wind-driven rain. This category of products must meet ASTM D1970 standards and have a label indicating this.

Self-Sealing Shingles Shingles that contain factory-applied strips of adhesive or spots.

Self-Sealing Strip, or Spot: A factory-applied adhesive that bonds shingle course together when exposed to heat from the sun.

Selvage – The portion of roll roofing that is covered by the next course. This allows for single or double coverage.

Shading – There may be slight differences in the shingle color due to normal manufacturing processes.

Sheathing – See Deck.

Shed Roof – A roof with only one slope. Does not contain hips, ridges valleys or gables.

Single-Color: This asphalt roofing system provides one layer of roofing material on top of the deck.

Slope – The slope of a roof. It is the ratio of the rise to the run in inches. A roof slope of 4/12 would have a 4 in increment every 12 inches.

Smooth-Surfaced Roof: A roll roofing system that uses ground talc and mica (coated).

Soffit – The underside of the eaves.

Soil Stack – A vent pipe that penetrates the roof.

Span is the horizontal distance between eave and eave.

Square – A unit for measuring 100 square feet of roof area.

Square Tab Shingles : Shingles that have the same size and are exposed to all tabs.

Standard Slope Application – Method for installing asphalt shingles on roof slopes from 4″ to 21″.

Starter strip: This is an asphalt roofing application at the eave. It provides protection through the addition of material beneath the joints and cutouts of the first course.

Steep Slope Application – Method for installing asphalt shingles on roof slopes greater that 21 inches per foot.

Step Flashing – Base flashing is used when a vertical surface meets an inclining roof plane.

Strip Shingles Asphalt shingles made of a single layer approximately three times longer than their width.

Synthetic underlayment: A synthetic underlayment that is usually made from polypropylene. It is an alternative to felt underlayment.

Tab – The strip shingles exposed by cutouts. (See Figure A.

Talc – See Back Surfacing.

Tear off: To tear down an existing roof system to the structural deck.

Telegraphing: Shingle distortions that can occur when a roof is placed on an uneven surface.

Three Dimensional Shingles: Refer to Laminated Shingles.

Top Layer: The portion of the roof that is covered by the next course after installation. (See Figure A.

UL: Underwriters Laboratories, LLC

UL label: This label is placed on packaging to indicate asphalt roofing’s fire- and wind resistance.

Underlayment : A layer of asphalt saturated felt or a specially engineered synthetic material that is used underneath roofing to provide extra protection for the deck.

Valley – The internal angle created by two sloped roof planes intersecting. (See Figure B.

Vapor Retarder : Any material that prevents water vapor from passing.

Vent: Any air outlet that extends through the roof deck, such as a stack or pipe. A device that ventilates the underside of the roof deck, such as a gable, soffit or roof.

Vent Sleeve – See Collar.

Woven valley: This is a method of building a valley. Shingles from either side of the valley are laid across the valley, and then woven together using alternate tracks. Valley flashing is not visible.

This post was written by a roofing professional at KCG Roofing. KCG Roofing is a premier roofing contractor in Florida! KCG Roofing has the experience and expertise to replace or repair your roof with quality materials and excellent craftsmanship. All our roofs are backed by a 15-year leak-free guarantee, the highest in the industry. We have been family-owned and operated for over 40 years. Click here to learn more.