Roofing Terminology and FAQ

Glossary of Roofing Terms


  • Algae – Rooftop fungus that can leave dark stains on roofing.
  • Angled Fasteners – Roofing nails and staples driven into decks at angles not parallel to the deck.
  • APA – American Plywood Association. Tests and sets standards for all varieties of plywood used in the U.S.
  • Apron Flashing – Metal Flashing used at chimney fronts.
  • ARMA – Asphalt Roofing Manufacturer’s Association. Organization of roofing manufacturers.
  • Asphalt – A bituminous waterproofing agent used in various types of roofing materials.
  • Asphalt Concrete Primer – Asphalt based primer used to prepare concrete and metal for asphalt sealant.
  • Asphalt Plastic Cement – Asphalt based sealant material meeting ASTM D4586 Type I or II. Used to seal and adhere roofing materials. Also called mastic, blackjack, roof tar, bull.
  • ASTM – The American Society for Testing and Materials. Organization that sets standards for a wide variety of materials, including roofing.


  • Back-surfacing – Granular material added to shingle’s back to assist in keeping separate during delivery and storage.
  • Blistering – Bubbles or pimples in roofing materials. Usually moisture related. In shingles, blisters are either moisture under the material or moisture trapped inside the material.
  • Blow-offs – When shingles are subjected to high winds and are forced off a roof deck.
  • Buckling – When a wrinkle or ripple effects shingles or their underlayments.


  • Closed-cut valley – A shingle valley installation method where one roof plane’s shingles completely cover the others. The top layer is cut to match the valley lines.
  • Corrosion – When rust, rot, or age negatively effect roofing metals.
  • Counter-flashing – The metal or siding material that is installed over roof-top base flashing systems.
  • Crickets – A peaked water diverter installed behind chimneys and other large roof projections. Effectively diverts water around projections.
  • Cupping – When shingles are improperly installed over an existing roof or are over-exposed, they form a curl or cup.


  • Deck – The substrate over which roofing is applied. Usually plywood, wood boards, or planks.
  • Dormer – A raised roof extending out of a larger roof plane.
  • Drip-edge – An installed lip that keeps shingles up off the deck at the edges and extends out over eaves and gutters, and prevents water from backing up under shingles.


  • Eaves – The roof edge from the fascia to the structure’s outside wall. In general terms, the first three feet across a roof is termed the eave.
  • End-laps – When installing rolled products in roofing, the area where a roll ends on a roof and is overlapped by the next section of rolled material (underlayments, rolled roofing).
  • Exposure – The area on any roofing material that is left exposed to the elements.


  • Fasteners – Nails or staples used in securing roofing to the deck. Felt-organic or paper-based rolled material saturated with asphalt to serve as roofing underlayment.
  • FHA – The Federal Housing Authority. Sets construction standards throughout the U.S.
  • Fiberglass mat – Fibers condensed into strong, resilient mats for use in roofing materials.
  • Flange – Metal pan extending up or down a roof slope around flashing pieces. Usually at chimneys and plumbing vents.
  • Flashing – Materials used to waterproof a roof around any projections through the roof deck.
  • Flashing cement – Sealant designed for use around flashing areas, typically thicker than plastic cement.


  • Gable roof – Traditional roof style; two peaked roof planes meeting at a ridge line of equal size.
  • Granules – Crushed rock that is coated with a ceramic coating and fired, used as top surface on shingles.


  • Hand-sealing – The method to assure sealing of shingles on very steep slopes, in high wind areas, and when installing in cold weather.
  • High nailing – When shingles are nailed or fastened above the manufacturer’s specified nail location.
  • Hip legs – The down-slope ridges on hip roofs.
  • Hip roof – A roof with four roof planes coming together at a peak and four separate hip legs.


  • Ice dam – When a snow load melts on a roof and re-freezes at the eave areas. Ice dams force water to “back-up” a roof and cause leakage.


  • “L” flashing – Continuous metal flashing consisting of several feet of metal. Used at horizontal walls, bent to resemble an L.
  • Laminated shingles – Shingles made from two separate pieces that are laminated together. Also called dimensional shingles and architectural shingles.
  • Laps – The area where roll roofing or rolled underlayments overlap one another during application (see also side laps and end laps).
  • Low slopes – Roof pitches less than 4/12 are considered low sloped roofs. Special installation practices must be used on roofs sloped 2/12 – 4/12.


  • Mansard – A roof design with a nearly vertical roof plane that ties into a roof plane of less slope at its peak.
  • Mats – The general term for the base material of shingles and certain rolled products.
  • Modified bitumen – Rolled roofing membrane with polymer modified asphalt and either polyester or fiberglass reinforcement.
  • Mortar – Mixture of sand, mortar, limestone, and water used in bonding a chimney’s bricks together.


  • Nail-guide line – Painted line on laminated shingles to aid in the proper placement of fasteners.
  • Nail-pop – When a nail is not fully driven it sits up off the roof deck.
  • Nesting – Installing a second layer of shingles, aligning courses with the original roof to avoid shingle cupping.
  • NRCA – The National Roofing Contractors Association. Respected national organization of roofing contractors.


  • Open valley – Valley installation using metal down the valley center.
  • Organic mat – Material made from recycled wood pulp and paper.
  • Organic Shingles – Shingles made from organic (paper) mats.
  • OSB – Oriented Strand Board. A decking made from wood chips and lamination glues.
  • Over-driven – The term used for fasteners driven through roofing material with too much force, breaking the material.
  • Over-exposed – Installing shingle courses higher than their intended exposure.


  • Pitch – Ratio of the rise of the roof to the span of the roof.
  • Power vents – Electrically powered fans used to move air from attics and structures.
  • Plastic cement – Asphalt based sealant. Also called bull, mastic, tar, asphalt cement.
  • Plumbing vents – Term used to describe plumbing pipes that project through a roof plane. Also called vent stacks.
  • Prevailing wind – The most common direction of wind for a particular region.


  • Quarter sized – Term for the size of hand sealant dabs; the size of a U.S. $.25 coin.


  • Racking – Method of installing shingles in a straight-up-the-roof manner.
  • Rake edge – The vertical edge of gable style roof planes.
  • Rigid vent – Hard plastic ridge vent material.
  • Roof louvers – Rooftop rectangular shaped roof vents. Also called box vents, mushroom vents, airhawks, soldier vents.
  • Roof plane – A roofing area defined by having four separate edges. One side of a gable, hip, or mansard roof.


  • Self sealant – Sealant installed on shingles. After installation, heat from the sun will activate sealant to seal the shingles to each other.
  • Selvage – The non-exposed area on rolled roofing. Area without granules. Designed for nail placement and sealant.
  • Side-laps – The area on rolled material where one roll overlaps the rolled material beneath it. Also called selvage on rolled roofing.
  • Side-walls – Where a vertical roof plane meets a vertical wall. The sides of dormers, etc.
  • Soffit ventilation – Intake ventilation installed under the eaves, or at the roof edge.
  • Starter strip – The first course of roofing installed. Usually trimmed from main roof material.
  • Steep slope roofing – Generally all slopes higher than 4/12 are considered steep slopes.
  • Step flashing – Metal flashing pieces installed at side-walls and chimneys for weatherproofing.


  • Tab – The bottom portion of traditional shingle separated by the shingle cut-outs.
  • Tear-off – Removal of existing roofing materials down to the roof deck.
  • Telegraphing – When shingles reflect the uneven surface beneath them. Shingles installed over buckled shingles may show some buckles.
  • Transitions – When a roof plane ties into another roof plane that has a different pitch or slope.


  • Under-driven – Term used to describe a fastener not fully driven flush to the shingle surface.
  • Underlayments – Asphalt based rolled materials designed to be installed under main roofing material, to serve as added protection.


  • Valleys – Area where two adjoining sloped roof planes intersect on a roof creating a “V” shaped depression.
  • Vapor – Term used to describe moisture laden air.
  • Ventilation – The term used in roofing for the passage of air from an enclosed space.


  • Warm wall – The finished wall inside of a structure; used in roofing to determine how to install waterproof underlayments at eaves.
  • Warranty – The written promise to the owner of roofing materials for material related problems.
  • Waterproof underlayments – Modified bitumen based roofing underlayments. Designed to seal to wood decks and waterproof critical leak areas.
  • Woven valleys – The method of installing valleys by laying one shingle over the other up the valley center.

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