This glossary contains many useful terms and definitions that will help you understand much of the work we do at ROOFCORP.

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G-90: a designation for galvanized metal sheet, indicating 0.90 ounces (26 g) of zinc per square foot, measured on both sides.

Gable: the vertical triangular portion of the end of a building having a double-sloping roof, from the level of the eaves to the ridge of the roof.

Gable roof: a single-ridge roof that terminates at gable end(s).

Galvalume: trade name for a metal alloy coating that is composed of aluminum, zinc and silicone.

Galvanic action: an electrochemical action that generates electrical current between two metals of dissimilar electrode potential.

Galvanic series: a list of metals and alloys arranged according to their relative electrolytic potentials in a given environment.

Galvanize: to coat steel or iron with zinc. Galvanized steel: steel coated with zinc for corrosion resistance.

Gambrel: a roof that has two pitches on each side, where the upper roof area has less slope than the lower roof areas.

Gauge: a metal thickness measurement.

Geocomposite: a prefabricated water drainage material used to relieve hydrostatic pressure against waterproofing and promote drainage.

Geotextile: a tightly woven fabric used to restrict the flow of fine soil particles and other contaminants while allowing water to pass freely through; used to protect drainage systems from clogging.

Girt: a horizontal beam that supports wall cladding between columns. Glass fiber insulation: blanket or rigid board insulation, composed of glass fibers bound together with a binder, faced or unfaced, used to insulate roofs and walls.

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

Glass mat: a thin mat of glass fibers with or without a binder.

Glaze coat: (1) the top layer of asphalt on a smooth-surfaced built-up roof membrane; (2) a thin protective coating of bitumen applied to the lower plies or top ply of a built-up roof membrane when application of additional felts or the flood coat and aggregate surfacing are delayed. (also see Flood coat.)

Gloss: the shine, sheen or luster of a dried film. Grain: a unit of measure in the English System of units; 7,000 grains equals 1 lb.; used as a measure of the weight of moisture in air.

Granule: (also referred to as mineral or ceramic granule) opaque, natural or synthetically colored aggregate commonly used to surface cap sheets, shingles, and other granule-surfaced roof coverings.

Gravel: coarse granular aggregate 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.

Groundwater level: at a particular site, the level, below which the subsoil and rock masses of the earth are fully saturated with water.

Grout: a mixture of cement, sand, and water used to fill cracks and cavities in masonry.

Gusset: used at the bottom of a steep-slope roof system valley, a large flat metal piece(s) wider than the valley to help prevent build-up at the base of the valley, either from debris or ice dam formations.

Gutter: a channeled component installed along the downslope perimeter of a roof to convey runoff water from the roof to the drain leaders or downspouts.

Gypsum board panels: cementitious board stock with noncombustible core primarily comprised of gypsum that is commonly used as a barrier board thermal barrier or cover board in a roof assembly.