G,H,I,

Dictionary of Roofing Terms

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Gable: A triangular-shaped portion of the end wall of a building directly under the sloping roof and above the Eave line. See Fig 1.

Gable Roof: A roof configuration that has gable ends. See Fig 1.

Gable-On-Hip Roof: A roof configuration with hips coming up from the eave corners that terminate into a gable roof.

Galvanize: To coat with zinc.

Galvanized Steel: Steel that is coated with zinc to aid in corrosion resistance. Galvanized steel for use in roofing should be Hot-Dipped Galvanized with a G-90 coating.

Gambrel: A roof that has two different pitches.

Gauge: A standard of measurement. For instance the thickness of sheet metal or the diameter of wire. The thicker the wire or metal, the lower the gauge.

Girder: A main beam upon which floor joists rest, usually made of wood or steel.

Grain: A unit of measure for the mass of moisture: a unit of weight equal to 0.002285 ounces or 0.036 dram.

Granule: A small aggregate, naturally or synthetically coloured, used to surface cap sheets, shingles, and other granule-surfaced roof coverings.

Gravel: Aggregate consisting of rock fragments or pebbles.

Gravel Stop: A flanged, sheet metal edge flashing with an upward projection installed along the perimeter of a roof to stop the flow of bitumen over the edge.

Grout: A thin mortar used to fill cracks in masonry and tile.

Grout (Non-Shrink): A cementitious material used to partially fill penetration pockets (pitch pans). A pourable sealer is used afterward.

Gutter: A channel installed along the downslope perimeter of a roof to convey runoff water from the roof to the drain leaders or downpipes. (See Fig 1)

Gutter Clips: Plastic brackets used to support plastic gutters.

Gutter Strap: Metal bands used to support metal gutters.

Half Gable Roof: See Shed Roof.

Hand-Tabbing: Applying spots of adhesive to shingle tabs.

Hatch: A unit used to provide access to a roof from the interior of a building.

Heat Transfer: Thermal energy going from an area of higher temperature to an area of lower temperature by conduction, convection, or radiation.

Hem: The edge created by folding metal back on itself. Metal is hemmed for safety and strength reasons.

Hip: The angle formed by the intersection of two sloping roof planes. (See Fig 1)

Hip Roof: A roof that rises by inclined planes on all sides of a building. The line where two adjacent sloping sides of a roof meet is called the Hip.

Hoist: A mechanical lifting device. A hoist can be hand or electrically operated.

Holiday: An area where a liquid-applied material is missing.

Honeycomb: Small voids left in concrete because the mortar failed to fill the spaces around the aggregate.

Humidity: The amount of water vapour in the air.

HVAC: Acronym for Heating, Ventilating, and Air Conditioning.

Ice Dam: Ice formed at the transition from a warm surface to a cold surface, such as along the overhang of a house. The build-up of ice is the result of ice or snow melting on the roof area over the warmer, living area of a building and then refreezing when it runs down and reaches the overhang.

Ignition Temperature: The minimum temperature at which a material will combust.

Impact Resistance: A roof assembly’s ability to withstand the impact from falling objects such as hail.

Impregnate: To saturate; in roofing, asphalt impregnated fibreglass roofing felts are fibreglass mats that have been completely permeated with asphalt bitumen.

Incompatibility: Descriptive of two or more materials which are not suitable for use together.

Infiltration: The process by which air leaks into a building. In which case heat loss results. To find the infiltration heating load factor (HLF), the formula to account for the extra BTU's needed to heat the infiltrated air is:

BTU/HR = building volume x air changes x BTU/cu.ft/hr xTD (TD is temperature difference).

Infrared Thermography: The use of an infrared camera to detect moisture in roof insulation.

Inorganic: Involving neither organic life nor the products of organic life; relating to compounds not containing hydrocarbon groups.

Insect Screen: Material used to inhibit an insect’s ability to enter a building through openings in a roof such as vents.

Inside Drain: A drain positioned on a roof in a location other than at the perimeter. It drains surface water inside the building through closed pipes to a drainage system.

Insulation: Generally any material which slows down or retards the flow or transfer of heat. See also Thermal Insulation.

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.

Internal Pressure: Atmospheric pressure inside a structure that correlates to the number and location of openings and air leaks.

Inverted Roof Membrane Assembly (IRMA®): A variation of the "Protected Membrane Roof Assembly" in which Styrofoam® brand insulation is used. IRMA® and Styrofoam® are registered trademarks of the Dow Chemical Company.

Although these pages are checked regularly and every care is taken with the information within. Delston can not accept any responsibility or liability for information or results displayed within due to third party interference.

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