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Glossary of 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 plywoods 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 affects shingles or their underlayments.


Closed-cut valley A shingle valley installation method where one roof plane’s shingles completely cover the other’s. The top layer is cut to match the valley lines.
Cobra® GAFMC’s respected brand name for ventilation products.
Corrosion When rust, rot or age negatively affect roofing metals.
Counter-flashing The metal or siding material that is installed over roof-top base flashing systems.
Country Mansion® & Country Estates™ GAFMC’s limited lifetime warranty shingle.
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 of the deck at edges, and extends shingles out over eaves and gutters, and prevents water from backing up under shingles.
Dubl-Coverage® Mineral Guard Roll roofing material with 19″ selvage edge for double coverage over roof deck.


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.


Gable roof Traditional roof style; two peaked roof planes meeting at a ridge line of equal size.
GAFCant® GAFMC cant strips for deflecting water away from flashing areas. Typically used on low slope roofs.
Golden Pledge® GAFMC’s strongest limited warranty for shingles. America’s strongest steep slope warranty.
Grand Sequoia® GAFMC shingle with wood shake appearance.
Grand Slate™ GAFMC shingle with slate appearance.
Granules Crushed rock that is coated with a ceramic coating and fired, used as top surface on shingles.


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. GAFMC Timberline® Series, Country Mansion® and Grand Sequoia® Shingles. 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, size of a U.S. 25¢ piece.


Racking Method of installing shingles in a straight up the roof manner.
Rake edge The vertical edge of gable style roof planes.
Release film The plastic sheet installed on the back of Weather Watch® and StormGuard® underlayments. Used for packaging and handling. Remove before installation.
Rigid vent Hard plastic ridge vent material.
Roof louvres 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.


Sawteeth The exposed section of double thickness on Timberline® Series shingles. Shaped to imitate wood shake look on the roof.
Self-sealant Sealant installed on shingles. After installation, heat and 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.
Shed roof Roof design of a single roof plane. Area does not tie into any other roofs.
Shingle-Mate® GAFMC’s shingle underlayment. Breather type with fiberglass backing to reduce wrinkles and buckles.
Side-laps The area on rolled material where one roll overlaps the rolled material beneath it. Also called selvage edge 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.
Smart Choice® Limited Warranty GAFMC’s standard shingle limited warranty.
Smart Choice® System Plus Limited Warranty GAFMC’s next grade of enhanced warranty. Extended coverage for owners.
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 weather-proofing.
StormGuard® GAFMC waterproof underlayment. Film surfaced rolled underlayment, 1.5 squares coverage per roll.


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.
Timberline® Series GAFMC’s trademark name for laminated wood shake style shingles.
TIMBERTEX® GAFMC enhanced Hip and Ridge Shingles.
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 shingles 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.
Weather Stopper® Integrated Roofing System™ GAFMC’s complete roofing system and components.
Weather Watch® GAFMC’s granule surfaced waterproof underlayment.
Woven Valleys The method of installing valleys by laying one shingle over the other up the valley center.