G90—A typical coating weight for galvanized sheet. Equates to 0.90 oz of zinc per sq. ft. total both sides.

Gable—A triangular portion of the endwall of a building directly under the sloping roof and above the eave line.

Gable roof—A ridged roof that terminates in gables.

Galvalume—Trade name for steel coated with aluminum-zinc for corrosion protection.

Galvalume sheet steel—A sheet steel product patented by Bethlehem Steel Corporation having a coating of corrosion resistant aluminum-zinc alloy applied by a continuous hot dip process.

Galvanic cell—A cell in which chemical change is the source of electrical energy. It usually consists of two dissimilar conductors in contact with each other and an electrolyte.

Galvanized steel—Steel coated with zinc for corrosion resistance.

Girder—A main horizontal or near horizontal structural member that supports vertical loads. It may consist of several pieces. Generally a large beam into which other beams frame.

Girt—A secondary horizontal structural member attached to sidewall or endwall columns to which wall covering is attached and supported horizontally.

Glass felt—Glass fibers bonded into a sheet with resin and suitable for impregnation in the manufacture of bituminous waterproofing, roofing membranes, and shingles.

Glass mat—A thin mat of glass fibers with or without a binder.
Glass transition—The reversible change in an amorphous polymer or in amorphous regions of a partially crystalline polymer from (or to) a viscous or rubbery condition to (or from) a hard and relatively brittle one.

Glaze coat—(1) The top layer of asphalt in a smooth surfaced built-up roof assembly; (2) A thin protective coating of bitumen applied to the lower plies or top ply of a built-up membrane, when application of additional felts, or the flood coat and aggregate surfacing are delayed.

Gloss—Subjective term describing the relative amount and nature of mirror- like reflection from a surface.

Grade—The term used when referring to the ground elevation around a building.

Grade beam—A concrete beam around the perimeter of a building carrying an exterior wall.

Grain—Weight unit equal to 1/7000 Ib, used in measuring atmospheric water vapor content.

Granule—See Mineral granules.

Gravel—Coarse, granular aggregate, with pieces larger than sand grains, resulting from the natural erosion of rock.

Gravel stop—A flanged device, frequently metallic, designed to prevent loose aggregate from washing off the roof and to provide a continuous finished edge for the roofing.

Grid—Plot of roof usually on 5 or 10 foot centers. Meterreadings are taken at intersections.

Grout—A mixture of cement, sand, and water used to fill cracks and cavities. Often used under base plates or leveling plates to obtain uniform bearing surfaces.

Gusset plate—A steel plate used to reinforce or connect structural elements.

Gutter—A channel member installed at the eave of the roof for the purpose of carrying water from the roof to the drains or down spouts.