Glossary Of Terms

ROOFING TERMINOLOGY AND DEFINITIONS

Caulk: To fill a joint with mastic, butyl or equivalent cements to prevent leaks.

Chalk Line: Used for alignment purpose this is a line made on the roof snapping a taut string or cord dusted with chalk.

Closure: Foam or Acrylic closure strip or roll to close the gap between the profile of the roofing panel(s) and deck or trims to prevent weather, debris and insects/animals from entry to the building.

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

Deck: Also know as decking. The surface installed over the supporting framing members of a building. It is the structural skin over a roof to which roofing is applied. Most new homes have "decking" made of plywood. There are two main types of decking commonly used:

  • Plywood: Plywood is strong, durable and light. Use only exterior grade plywood for decking. The thickness of the plywood depends on the spacing of the rafters. The most common thickness used is 0.5".
  • OSB: Oriented Strand Board (OSB) is more economical than plywood but not as strong as plywood and does not hold screws as well as plywood. One side has a slip resistant coating and should be placed facing up.

Dektite/Master Flash/Pipe Flashing: Pre-formed flange (flashing) placed over a vent pipe to seal the roof around the vent pipe opening. Also called a pipe boot.

Dormer: A framed window unit projecting through the sloping plane of the roof.

Drip Edge: A flashing 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. Trim that goes on these areas may be referred to as "eave trim" – "eave flashing" – or sometimes "drip edge".

End-Lap: Where one panel or flashing ends and the other begins, or the distance in which the panel or flashing overlap one another to avoid moisture seeping through to the decking.

Felt: A flexible sheet that is saturated with asphalt and used as a protective underlayment - often referred to as "...the second line of defence".

Field Cut: Manually cutting with snips, shears or a blade, metal panels or trims to properly fit and install where the length or angles need to be altered. Field cuts are always required on the panels in the roof hips, valley’s and gable end treatments.

Flashing: Pieces of special trim 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, valleys, etc.

  • Plumbing vent flashing (see Dektite/Master Flash): 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 slope.
  • Step Flashing: Flashing application method used where a vertical surface meets a sloping roof plane.
  • 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 panels that are not trimmed properly.

Flashing Cement: In the application of metal roofing flashing cement is usually butyl (purchase the best grade available). This is used to further seal any potential leaks, usually at areas where a flashing was applied. A small bead of flashing cement where the flashing comes in contact with a vertical wall is a good idea.

Gable: The upper portion of a sidewall that comes to a triangular point at the ridge of a sloping roof. Trim that goes on this part of a roof is called "gable or rake trim".

Gable Roof: A type of roof containing sloping planes on each side of the ridge. Contains a gable at each end.

Gambrel Roof: 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. Contains a gable at each end.

Hip: The inclined external angle formed by the intersection of two sloping roof planes. 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. This type of roof does not contain a gable.

Ice Dam: Ice dams occur when snow near the eaves of warm roofs (roofs without adequate ventilation) melts and runs down the roof to the overhang cools and freezes. If the snow continues this melt and freeze process an ice dam can form that can seep under the roofing material, through the decking and into the house. This, of course, can cause serious roof leaks – even in freezing temperatures.

The best prevention of ice dams is a well ventilated (cool) roof. For additional protection, it is recommended that you install a layer of impermeable ice and water membrane (Ice & Water Shield) between the deck surface and metal roofing. 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 cause extensive damage.

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

Lean-to Roof: A roof with one slope only that is built against a higher wall.

Low Slope Application: Method of installing roofing material on roof slopes between two and four inches per 12 inches.

Major Rib: Steel Panels that have a profile have major ribs and can have minor ribs. The Major rib is the section of panel that Measures the Highest from the flat of the profile.

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. This type of roof contains no gables.

Membrane: A flexible or semi-flexible material, which functions as the waterproofing component in a roofing or waterproofing assembly, and whose primary function is to prevent water seepage.

Metal Drip Edge: This refers to trim, usually gable and eave trim, that has a slight bend at the edge which facilitates water runoff, away from the building.

Minor Rib: Where a steel panel has major and minor ribs, the Minor rib is the section of the panel that is raised higher than the flat of the panel but lower than the major rib.

Oil-Canning: Perceived waviness in the flat area of metal roofing and metal siding panels.

Open Valley: Method of roofing in which the roofing material on both sides of the valley is trimmed along a chalk line snapped on each side of the valley, leaving the valley flashing exposed. Metal roofing always has this feature.

Overhang: The portion of the roof structure that extends beyond the exterior walls of the building.

Pitch: Also known as "slope". Pitch is the measurement of how steep a roof is. For example, if a roof is a 4/12 pitch, the roof rise is 4" for every horizontal run of 12". 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.

Rafter: The supporting framing member immediately beneath the deck, sloping from the ridge to the eave.

Rake: The inclined edge of a sloped roof over a wall from the eave to the ridge. These two slopes meet at the peak or ridge. Trim that goes on these slopes is referred to as "gable or rake trim".

Re-cover (overlay): The installation of a new roof system over an existing system without removing the existing system.

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

Ridge: The uppermost, horizontal external angle formed by the intersection of the sloping roof planes. Trim that covers this area is called ridge cap.

Rise: The vertical distance from the eave line to the ridge.

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

Shed Roof: A roof containing only one slope. Has no hips, ridges, valleys or gables.

Slope: The degree of roof incline expressed as a ratio of the rise, in inches, to a run of 12". See "pitch".

Slope Application: Divided into three categories, this is the application of roofing materials to a roof based upon its slope or pitch. The three categories are known as "steep slope", "normal slope" and "low slope".

  • Steep Slope - Method of installing roofing material on roof slopes greater than 8" per 12".
  • Normal Slope – Method of installing roofing material on roof slopes between 4" and 8" per 12".
  • Low Slope – Method of installing roofing materials on roof slopes between 2" and 4" inches per 12".

Soffit: The finished underside of the eave.

Span: The horizontal distance from eave to eave.

Square: A unit of roof measurement covering 100 square feet.

Strapping: Also known as purlins or battens can be 1" x 4" or 2" x 4" wood strips nailed to the roof deck or rafters across the horizontal face, upon which the roofing is attached. The new roof being elevated slightly, the strapping contributes to the roof having airflow which can help disperse temperatures in the heat of the day. Installing strapping over an old roof also gives the ability to do some leveling by using shims between the strapping and the irregularities of the old roof surface. Strapping is, in some cases, attached to the roof decking to give a secure base to anchor the roofing materials because many OSBs (chip board sheets appearing much like plywood) will not hold a screw properly.

Synthetic Underlayment: This is made from a woven black polypropylene with polymer. It is UV resistant, self sealing where nails have penetrated it for attachment purposes and is slip resistant. Synthetic underlayment is vastly superior to felt and is recommended under metal roofs.

Tear off: Removing an existing roof.

Telegraphing: A distortion that may arise when a new roof is applied over an uneven surface.

Underlayment: This can be felt (see felt) or synthetic underlayment (see synthetic underlayment).

Valley: The internal angle formed by the intersection of two sloping roof planes to provide water runoff. Trim that goes in this area is valley trim.

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

White Rust/Oxidation: White rust on bare galvanized metal is the result of zinc oxidation in the absence of oxygen. This occurs in coil or bundles of sheet metal that are nested and absorb moisture from humidity in the air or direct rainfall. The oxidation appears as a white chalky build-up on the surface of the metal. This can be stopped by applying a vinegar solution or light oil, such as WD-40.

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