Glossary of Roofing Terms

You might have heard a number of unfamiliar terms in discussions about roofing. We have put together the following glossary so you can better understand roofing products, services and techniques. Please don’t hesitate to contact us if you have any other roofing questions.


Algae – Fungus that can develop on rooftops and leave dark stains.

Angled fasteners– Nails and staples that are driven into the roofing deck at an angle, not parallel.

APA – American Plywood Association. Carries out testing and sets standards for all the different plywoods used in the U.S..

Apron flashing – Metal flashing commonly used on chimney facings.

ARMA – Asphalt Roofing Manufacturer’s Association.  Trade association for roofing manufacturers.

Asphalt – A waterproof bituminous agent used in a variety of roofing materials.

Asphalt concrete primer – an asphalt-based primer for preparing concrete and metal to be sealed with asphalt.

Asphalt plastic cement – Asphalt based sealant, meeting standard specification ASTM D4586 Type I or II. For sealing and/or binding roofing materials. Also called mastic, blackjack, roof tar, bull.

ASTM -The American Society for Testing and Materials. Sets standards for many industrial materials, including roofing materials.


Back-surfacing – Fine mineral material applied to the back of shingles to keep them from sticking together during delivery and storage.

Blistering – Raised bumps on roof shingles that are usually caused by trapped moisture

Blow-offs – Shingles that loosen and come off the roof deck in high winds.

Buckling – Wrinkles or ripples that appear along roof shingles.


Closed-cut valley – a method of shingling a roof valley where shingles from one roof plane cover the valley underneath shingles from the other plane, which are cut to fit the valley.

Cobra® – GAFMC’s a brand of ventilation products.

Corrosion – The effect of rust, rot or age on roofing materials.

Counter-flashing – additional metal or siding material installed over base flashing to give more protection

Country Mansion® & Country Estates™ – GAFMC shingle with a limited lifetime warranty.

Crickets – A ridged device used to divert water around roof projections, like a chimney or large vent.

Cupping – Old or improperly installed shingles, can curl around the edges, forming a cup shape.


Deck – The base or substrate upon which roofing materials are applied. Generally made of plywood sheets, wood boards or planks.

Dormer – A roofing element that protrudes from a larger sloping roof.

Drip-edge – A sheet metal edge, installed under shingles along the edge of the deck and extending over the eaves to keep moisture and debris from building up and damaging shingles, substrates or other parts of the home.

Dubl-Coverage® Mineral Guard – Rolled roofing material that provides double coverage with a 19” selvage edge


Eaves – The edge of a roof from the building structure to the end of the fascia.

End-laps – The overlap between two sections of rolled roofing material.

Exposure – The part of roofing material left open to the elements.


Fasteners – Nails, screws or staples used to secure roofing materials to the deck. Rolls of paper or felt-organic material, treated with asphalt, serving as a base layer for roofing.

FHA-The Federal Housing Authority. Sets standards for construction in the U.S.

Fiberglass mat – roofing materials made of short strands of fibreglass.

Flange -sheet of metal used in addition to flashing around chimneys and vents

Flashing – Metal material used to direct water away from roof projections, valleys and edges.

Flashing cement – Thick sealant used to seal flashing to a roof


Gable roof – A style of roof that slopes from a peak to the eaves, forming a triangle.

GAFCant® – a brand of cant strips used to divert water from flashing.

Golden Pledge® – GAFMC’s brand of shingles with the best warranty in the U.S.

Grand Sequoia®– GAFMC brand of shingles made to look like wood shakes.

Grand Slate™– GAFMC brand of shingles made to look like slate.

Granules – Protective shingle surface coating, made of ceramic coated crushed rock.


Hand-sealing – An enhanced method of sealing shingles on steep slopes, in areas of strong wind and in cold weather installations.

High nailing – Using nails or fasteners on shingles above the area specified by the manufacturer for fastening.

Hip legs – The corner ridges on a hip roof.

Hip roof – A roof style where all four sides slope down from a peak to the eaves.


Ice Dam – Ice that forms along the eaves that can cause leaks by backing-up water on the roof.


“L” flashing – “L” shaped metal flashing, available in varying gauges, sizes and lengths.

Laminated shingles – Shingles made from laminating together two separate materials – also known as architectural shingles and dimensional shingles.

Laps – The over lap between sections of rolled roofing or rolled underlayment.

Low slopes – A roof pitch below 4/12. Slopes from 2/12 – 4/12 require different installation procedures.


Mansard – A style of hip roof with two different slopes along each side with the lower slope being very steep (almost vertical.)

Mats – An overall term for the base material of shingles and some rolled roofing materials.

Modified bitumen – A polyester or fibreglass reinforced rolled roofing membrane with asphalt modified with polymers for additional protection.

Mortar – A mixture of sand and cement used to bind blocks and bricks and fill gaps between them.


Nail-guide-line – The imprinted line on shingles that indicates where fasteners should be placed

Nail-pop – A raised roofing nail that has not been fully driven.

Nesting – A roofing method designed to avoid cupping by adding a second layer of shingles, aligning courses with the first.

NRCA– The National Roofing Contractors Association. Trade association for roofing contractors.


Open valley – A roof valley where the metal valley flashing is open down the centre of the valley between shingles.

Organic mat – Roofing materials made from recycled paper and wood pulp.

Organic Shingles – Shingles manufactured with organic mats.

OSB – Oriented Strand Board, or wafer board, made by laminating wood chips together – used for roof decks.

Over-driven – A roof fastener that has been driven through the roof material, damaging the material.

Over-exposed – Installing a course of shingles with more surface area exposed than that recommended by the manufacturer.


Pitch – ratio between the height and span of a roof.

Power vents – Electric fans used to ventilate attics.

Plastic cement – Sealant made from asphalt – also called bull, mastic, tar, asphalt cement.

Plumbing vents – Vent that release gasses from plumbing systems.

Prevailing wind – The direction from which wind usually blows in any given area.


Quarter sized – Used to indicate the size of dabs for hand sealant – approximately the size of a 25¢ coin.


Racking – A method a laying roof shingles up the roof avoiding moving back and forth across the roof.

Rake edge -The vertical edge of gable style roof planes.

Release film– Plastic sheet used on the back of Weather Watch® and StormGuard® underlayments for packaging and protection – should be removed before installation.

Rigid vent – hard plastic vents used in roofing.

Roof louvers – rectangular roof vents that allow air to escape from attics

Roof plane – the area of a roof occurring on a single plane. One side of a roof unbroken by ridges or valleys.


Sawteeth – The exposed double-thickness edge of Timberline® Series shingles. Designed to replicate the look of a wood shake

Self-sealant – Shingles coated with sealant on the deck-side that is activated by heat from the sun following installation.

Selvage – The area of rolled roofing, uncoated by granules, used for fastening or sealant.
Shed roof – A roof with a single plane, not connected to any other roof planes.

Shingle-Mate® – GAFMC’s brand of shingle underlayment. Fiberglass backing reduces buckling and wrinkles.

Side-laps – The area of overlap between one layer of rolled roofing material and the layer below it.

– Where a roof plane connects to a vertical wall, such as the side of a dormer.

Soffit ventilation
– Attic ventilation installed under a roof’s eave.

Smart Choice® Limited Warranty
– GAFMC’s standard shingle limited warranty.

Smart Choice® System Plus Limited Warranty
– GAFMC’s extended coverage warranty.
Starter strip – Specially made strip of material, or cut shingles, placed along roof edges over which the first course of exposed shingles are placed.
Steep slope roofing – A roof with a slope greater than 4/12.

– Weather-proofing metal flashing used at side-walls and chimneys..

– GAFMC brand of waterproof underlayment. Rolled underlayment with a film surface. 1.5 squares coverage per roll.


Tab – the section of a roof shingle separated by cut-outs.

Tear-off – Complete removal of roofing material to the deck.

Telegraphing – When shingles take on the shape of the surface they are installed upon.  Shingles placed over ridges might show the ridge.
Timberline® Series– GAFMC’s brand of laminated wood shake style shingles.

TIMBERTEX®– GAFMC brand of enhanced Ridge and Hip Shingles.

– The point at which a roof plane ties into another roof plane of a different pitch.


Under-driven – A roof fastener that is not driven in enough to be flush with the roof surface.

Underlayments – Rolled asphalt-based material installed under the main roofing material for added protection.


Valleys – The “V” shaped intersection formed between two adjoining roof planes.

Vapor – Air with a heavy moisture content.

Ventilation – Allowing air to pass from and enclosed space, such as an attic.


Warm wall – A structure’s finished inside wall, used to determine how to install underlayment at the eaves.

Warranty – The specification of the protection offered by a roofing materials manufacturer to the purchaser in case of problems with the materials.
Waterproof underlayments – Underlayments modified with bitumen to provide a waterproof seal for roof decks and high leak areas.
Weather Stopper® Integrated Roofing System™– GAFMC’s complete roofing system and components.

Weather Watch®– GAFMC’s brand of granule surfaced waterproof underlayment.

Woven Valleys– Layering of one shingle over another along the centre of a valley.

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