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Roofing Terminology

At D. Ross Renovations & Roofing, we want our customers to be as informed as possible so that they can make the best decisions about their home’s roof. Here are some common roofing terms and definitions that you may hear during the course of your roofing project. If you have any questions about any part of your roof or the roofing process, please do not hesitate to ask for an explanation!​

Attic – The open area above the ceiling and under the roof deck of a steep-sloped roof.

Asphalt Shingle – A shingle manufactured by coating a reinforcing material (felt or fibrous glass mat) with asphalt and having mineral granules on the side exposed to the weather.

Brick Flashing- The purpose of brick flashing is to direct water away from the wall surface.

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

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

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.

Collar – Pre-formed flange placed over a vent pipe to seal the roof around the vent pipe opening. The collar is also called a vent sleeve.

Condensation – 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.

Course – A row of shingles or roll roofing running the length of the roof.

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

Cut-Out – The open portions of a strip shingle between the tabs.

Deck or Decking – The structural “skin” of a roof over which roofing is applied. Most new homes have decking made of plywood. There are four main types of decking commonly used on residential roofing projects:

1. Plywood: Plywood is strong, durable, and light. It comes in many grades with ratings from A to D. Use only exterior grade plywood for decking. The thickness of plywood depends on the spacing of the rafters.

2. OSB: Oriented strand board (OSB) is cheaper than plywood, but not as strong as plywood, and does not hold nails as well as plywood. One side has a slip resistant coating and should be placed facing up.

3. Tongue and groove 2-by-6: If a roof will be seen from the inside (no ceiling installed), tongue and groove is used. It is a wood decking that provides great insulation without additional rigid roof insulation in moderate climates. Also, the boards can be painted or stained on the inside to match the interior.

4. Step sheathing: Step sheathing is used alone or in combinations with solid sheathing for installation of tiles or shakes. Step sheathing allows air circulations under the tiles by using 1-by-6 or 2-by-6 boards that are evenly spaced so that air can move under the tiles or shakes.

Dormer – A framed window unit that projects through the sloping plane of a roof.

Downspout – A pipe for draining water from roof gutters. A downspout is 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.

Eaves – The horizontal, lower edge of a sloped roof.

Edge Venting – The installation of a vent material along the roof edge (e.g., Starter Vent) as part of a ventilation system. Edge vent material should be used in conjunction with other venting material (e.g., ridge vent) as it not intended for use by itself.

Exposure – Portion of the shingle exposed to the weather. Exposure is measured from the butt of one shingle to the butt of the next.

Fascia – Horizontal trim at the eaves that covers the rafter ends.

Felt – A flexible sheet that is saturated with asphalt and used as an underlayment. Sometimes called “tar paper”, the GAF

Flashing – Flashing systems are a site where many roof leaks occur. Whether flashing is located where roof planes intersect, around vents, or at the chimney, flashing systems should be replaced when a new roof is being installed. Think of flashing like a kind of metal angle around chimneys, dormers, vents, valley areas, and skylights. A flashing system that is properly installed will have water run over joints, not in them.

Flashing is to be installed on top of the ice and water membrane with proper Self-Sealing Flashing Screws to prevent leaking. All to often, contractors cut corners by installing flashing with roofing nails. We are called to repair many leaks each year due to this poor workmanship

Brick Flashing: The purpose of brick flashing is to direct water away from the wall surface.​

Flashing is one of the most important elements of the roof because it seals the seams and joints of the roof–the locations where leaks are most likely to occur. Often, flashing is not maintained well, or installed correctly in the first place. Check for the following signs that your flashing needs maintenance or repair:

•Rusting of metal flashing

• Excess leaves and debris in valleys or seams of the roof (can lead to rusting and corroding of the metal)

•Prolonged exposure to the elements such as moisture, UV rays, climate changes–especially when asphalt compounds or caulking material is used. Look for cracks, loss of elasticity and delamination.

Valley Flashing: Valley flashing is a type of roofing material that is used to waterproof and protect the intersection where two roof planes meet. It is typically made from metal, such as aluminum. Valley flashing is an important component to your roofs flashing system. It protects the critical area of the roof where two slopes come together to form a valley. When properly installed, this flashing will effectively direct the water run-off down the roof and into the gutters

Gable – 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. A gable roof typically contains a gable at each end.

Gambrel – 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. A gambrel roof usually contains a gable at each end, just like a standard gable roof.

Granules – Ceramic-coated colored crushed rock that is applied to the exposed surface of asphalt roofing products.

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

Hip – The inclined external angle formed by the intersection of two sloping roof planes. The hip runs from the ridge to the eaves.

Hip Roof – A type of roof containing sloping planes of the same pitch on each of four sides. A hip roof contains no gables.

Ice Dam – Ice dams occur when snow melts near the ridgelines of warm roofs (roofs without adequate ventilation). As the water runs down the roof to the overhang, it cools and freezes. If the snow continues this melt and freeze process, an ice dam can form that can seep under the shingles, through the decking and into the house. This, of course, can cause serious roof leaks–even in freezing temperatures. The best prevention to ice dams is a well-ventilated (cool) roof. Additional protection for your roof can be applied with an impermeable ice and water membrane. The membrane is installed on top of the decking, under the roofing material.

Prevention of ice dams can be done with the use of electric cables along the eaves of the roof (where the dams usually form). However, new ice dams can form above the cables and still cause extensive damage. The use of electric cables voids your shingle warranty. Another emergency solution to ice dams is to fill a sock or nylon with calcium chloride. Lay the stocking vertically across the ice dam. The calcium chloride will melt the ice and release the water so that it can drain outside, and not inside your roof. This also voids any shingle warranty.

Ice Guard – A self-adhering, waterproofing shingle underlayment designed to protect against water infiltration due to ice dams or wind-driven rain. GAF, the brand preferred by contractors, is called Weather Watch.

Intake Ventilation – The part of a ventilation system used to draw fresh air in. Usually vents installed in the soffit or along the eaves of a building.

Laminated Shingles – Strip shingles containing more than one layer of tabs to create extra thickness. Laminated shingles are also called three-dimensional shingles or architectural shingles.

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.

Non-Prorated Warranty – A warranty which provides full replacement costs for the item(s) covered during the full term of the warranty. In contrast, a prorated warranty merely reimburses a percentage of replacement costs, depending on the age of the roof.

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.

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

Pitch – Also known as “slope”, pitch is the measure of how “steep” a roof is. For example, if a roof is “4 in 12″, the roof rises 4 inches for every horizontal run of 12 inches. The pitch of the roof is a big factor in determining the kinds of materials that can be used and the longevity of the roof. Usually, a steeper roof (higher pitch) will last longer due to its better drainage capabilities.

Racking – Roofing application method in which shingle courses are applied vertically up the roof rather than across and up. Not a recommended procedure.

Rafter – The supporting framing member immediately beneath the deck, sloping from the ridge to the wall plate.

Rake – The inclined edge of a sloped roof over a wall from the eave to the ridge.

Re-roofing – Installing a new roof system on a building that is not new.

Ridge – The uppermost, horizontal external angle formed by the intersection of two sloping roof planes.

Ridge Vent – Vent placed along the RIDGE of the roof. It allows ventilation of the roof by raising the LEVEL of the RIDGE slightly leaving room for air flow. A filtration fabric placed in the side vents allows air to move through while preventing insects from entering.

Rise – The vertical distance from the eaves line to the ridge.

Run – The horizontal distance from the eaves to a point directly under the ridge. One half the span.

Sheathing – Exterior grade boards used as a roof deck material. “Step sheathing” is used alone or in combinations with solid sheathing for installation of tiles or shakes. Step sheathing allows air circulations under the tiles by using 1-by-6 or 2-by-6 boards that are evenly spaced so that air can move under the tiles or shakes.

Shed Roof – A roof containing only one sloping plane. Has no hips, ridges, valleys or gables.

Slope – The degree of roof incline expressed as the ratio of the rise, in inches, to the run, in feet.

Soffit – The finished underside of the eaves.

Soil boot – A vent pipe that penetrates the roof.

Span – The horizontal distance from eaves to eaves.

Square – A unit of roof measure covering 100 square feet.

Starter Strip – Asphalt roofing applied at the eaves that provides protection by filling in the spaces under the cutouts and joints of the first course of shingles.

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

Step Flashing – Flashing application method used where a vertical surface meets a sloping roof plane.

Tab – The exposed portion of strip shingles defined by cutouts.

Three-dimensional Shingles – The most popular type of asphalt shingle usually 12″ x 36″ in size with three tabs.

Underlayment – A layer of asphalt saturated (sometimes referred to as tar paper) which is laid down on a bare deck before shingles are installed to provide additional protection for the deck.

Valley – The internal angle formed by the intersection of two sloping roof planes to provide water runoff.

Vent – Any outlet for air that protrudes through the roof deck such as a pipe or stack. Any device installed on the roof, gable or soffit for the purpose of ventilating the underside of the roof deck.

Woven Valley – Method of valley construction in which shingles from both sides of the valley extend across the valley and are woven together by overlapping alternate courses as they are applied. The valley flashing is not exposed. This method is not approved by building code in Ontario.


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