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| G-90 | A coating weight for galvanized sheet metal, 0.90 ounces of zinc per sq. ft., measured on both sides of the sheet. |
| Gable | A triangular-shaped portion of the endwall of a building directly under the sloping roof and above the Eave line. |
| Gable Roof | A roof configuration that has gable ends. |
| Gable-On-Hip Roof | A roof configuration with hips coming up from the eave corners that terminate into a gable roof. |
| Galvalume | Trade name for a protective coating composed of aluminum zinc. |
| Galvanic Action | A reaction between different metals in the presence of an electrolyte. |
| 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. |
| Geodesic Dome | A geodesic dome uses a pattern of self-bracing triangles in a pattern that gives maximum structural advantage, thus theoretically using the least material possible. (A "geodesic" line on a sphere is the shortest distance between any two points.) The first contemporary geodesic dome on record was designed by Walter Bauersfeld. |
| Girt | A horizontal beam place between support columns that is used for attaching wall cladding. |
| Glass Felt | (1)In the manufacturing of roofing materials - a sheet comprised of bonded glass fibers prior to being saturated with bitumen; <BR><BR>(2) short for asphalt or coal tar saturated fiberglass felt membrane. |
| Glaze Coat | (1) The uppermost layer of asphalt on a smooth-surfaced built-up roof membrane, usually a reflective surfacing is installed over it; <BR><BR>(2) A thin coat of bitumen applied to help protect the roof membrane when application of additional felts or the flood coat and aggregate surfacing are delayed. |
| 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 colored, 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 (usually sheet metal) installed along the downslope perimeter of a roof to convey runoff water from the roof to the drain leaders or downspouts. |