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; (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; (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.