Glossary of Roofing and Waterproofing Terms

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G-90: a typical coating weight for galvanized metal sheet. Equates to 0.90 ounces (26 g) of zinc per sq. ft., measured on both sides.

Gable: a triangular portion of the endwall of a building directly under the sloping roof and above the eave line. (See Figure 10.)

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Gable-Shaped Roof: a single-ridge roof that terminates at gable end(s). (See Figure 11.)

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Galvalume~: trade name for a coating, used over metal, that is composed of aluminum zinc for corrosion protection.

Galvanic Action: an electroylic reaction between dissimilar metals in the presence of an electrolyte.

Galvanize: to coat with zinc.

Galvanized Steel: steel coated with zinc for corrosion resistance.

Gambrel: a roof that has two pitches on each side. (See Figure 12.)

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Gauge: a measurement of rating metal thickness.

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

Geodesic Dome: a rounded structure made of short, straight, triangular sections that form polygons. (See Figure 13.)

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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 for protection of drainage systems from clogging.

Girt: a horizontal beam that supports wall cladding between columns.

Glass Felt: a sheet composed of bonded glass fibers, suitable for impregnation and coating in the manufacture of bituminous roofing and waterproofing materials, and shingles.

Glass Mat: a thin mat composed of glass fibers, woven or non-woven, with or without a binder. This mat may serve as reinforcement for certain roof materials and membranes.

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 used to measure the mass of moisture.

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: aggregate resulting from the natural erosion of rock.

Gravel Stop: a low profile upward-projecting metal edge flashing with a flange along the roof side, usually formed from sheet or extruded metal. Installed along the perimeter of a roof to provide a continuous finished edge for roofing material. Acts as a bitumen-stop during mop application of hot bitumen along a perimeter edge.

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.

Grout (Non-Shrink): a cementitious material used to fill pitch-pans/pockets, prior to the application of a pourable sealer.

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.


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