Know Your Roofing Terms
At Muth & Company 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!
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.
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.
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.
The change of water from vapor to liquid when warm, moisture-laden air comes in contact with a cold surface.
That portion of the flashing attached to a vertical surface to prevent water from migrating behind the base flashing.
A peaked saddle construction at the back of a chimney to prevent accumulation of snow and ice and to deflect water around the chimney.
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:
- 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.
- 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.
- 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.
- 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.
A shingle that is textured, overlayed, or laminated and designed to produce a three-dimensional effect. Similar to Laminated shingle and Architectural shingle.
A non-corrosive, non-staining material used along the eaves and rakes to allow water run-off to drip clear of underlying construction.
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.
Portion of the shingle exposed to the weather. Exposure is measured from the butt of one shingle to the butt of the next.
A flexible sheet that is saturated with asphalt and used as an underlayment. Sometimes called "tar paper", the GAF brand used is called Shingle Mate, made with a fiberglass mat instead of a paper mat.
Pieces of metal or roll roofing used to prevent seepage of water into a building around any intersection or projection in a roof such as vent pipes, chimneys, adjoining walls, dormers and valleys. Galvanized metal flashing should be minimum 26-gauge. There are 4 main types of flashing used in residential roofing systems:
- Valley flashing: This flashing is used in open valleys of the roof. Most often leaks are found in the valley flashings due to flashing that is nailed too tightly to the decking or shingles that are not trimmed far enough off the flashing.
- Plumbing vent flashing: Plumbing vent flashing prevents rainwater from running into holes cut for pipes in the roof. This flashing is sold according to the size of the vent pipe and the roof angle. Roofing material is installed over the flashing.
- Lead flashing: When working with tile roofs, lead flashing is used. In the case of a plumbing vent flashing, the lead flashing is actually molded to the shape of the tile's surface. Then the top of the lead flashing is covered by the next tile to prevent water from seeping under the flashing.
- Step flashing: When a chimney or dormer wall intercepts the slope of the roof, step flashing is used. Step flashing is usually a metal piece that is bent in the middle, so that one end lays on the roof, and the other against the vertical wall of the dormer or chimney.
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. In many cases the flashing can be cleaned and then repaired, relaminated or repainted (even in the case of rust). In other cases, the flashing may need to be replaced.
The upper portion of a sidewall that comes to a triangular point at the ridge of a sloping 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.
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.
Ceramic-coated colored crushed rock that is applied to the exposed surface of asphalt roofing products.
The inclined external angle formed by the intersection of two sloping roof planes. The hip runs from the ridge to the eaves.
A type of roof containing sloping planes of the same pitch on each of four sides. A hip roof contains no gables.
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. Temporary prevention of ice dams can also be done through 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. 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.
A self-adhering, waterproofing shingle underlayment designed to protect against water infiltration due to ice dams or wind-driven rain. GAF brand used would be called Weather Watch.
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.
Strip shingles containing more than one layer of tabs to create extra thickness. Laminated shingles are also called three-dimensional shingles.
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. Contains no gables.
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.
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.
That portion of the roof structure that extends beyond the exterior walls of a building.
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.
Roofing application method in which shingle courses are applied vertically up the roof rather than across and up. Not a recommended procedure.
The supporting framing member immediately beneath the deck, sloping from the ridge to the wall plate.
The uppermost, horizontal external angle formed by the intersection of two sloping roof planes.
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.
The horizontal distance from the eaves to a point directly under the ridge. One half the span.
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.
The degree of roof incline expressed as the ratio of the rise, in inches, to the run, in feet.
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.
Method of installing asphalt shingles on roof slopes greater than 21 inches per foot.
Flashing application method used where a vertical surface meets a sloping roof plane.
The most popular type of asphalt shingle usually 12" x 36" in size with three tabs.
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.
The internal angle formed by the intersection of two sloping roof planes to provide water runoff.
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.