Copyright Goodheart-Willcox Co., Inc. 120 Section 3 Specifications and Materials Wall studs, lintels, window and door frames, and floor joists are made from heavy-gage metals. Thin- gage metals are used for such items as roof flashing, ductwork, roofing, and wall siding. Steel in Construction Steel is the most widely used metal in construction, with applications ranging from structural support to reinforcement to decorative uses. Structural steel is the term applied to hot-rolled steel l sections, shapes, and plates, Figure 7-18. This includes bolts, rivets, and bracing. Structural steel shapes are formed by passing heated strips of steel through a succession of rollers that gradu- ally form the metal into the required shape. Structural steel shapes are available in a number of sizes and weights. Figure 7-19 illustrates some standard shapes, with identifying symbols and designations. A typical designation for a wide-flange beam would be W12×16, which indicates a beam 12″ in depth that ″ weighs 16 pounds per linear foot. A typical designation for a lightweight beam, sometimes called an I-beam, would be S8×23. This indicates that the beam is 8″ in ″ depth and weighs 23 pounds per linear foot. Steel members are connected to form building frames, Figure 7-20. The frame is usually then hidden behind other materials, such as a masonry wall, precast panels, or sheet metal siding. Steel angles (sometimes called angle iron) are used as bracing in steel framing and to construct open-web steel joists and many other products, Figure 7-21. Angles are designated with the letter “L,” followed by the lengths and thickness of the “legs.” For an angle identified as L3×3×1/2, both legs are 3″ long and 1/2″ ″ thick. ″ Surface Treatments Metals used in construction may have protective or decorative surface treatments applied to them. Treatments include: • Chroming. Applying chromium as a finish to a metal surface. • Galvanizing. Coating steel or iron with zinc to resist rusting. Galvanized iron is widely used for flashing and other applications where weather tends to corrode metals. • Rusting. Certain steels are designed to form a protective layer of rust, a reddish-brown surface t coating formed when the metal is exposed to moisture and air. • Electroplating. An adherent metallic coating deposited by means of an electrical current. Metal Gages Metal materials less than 1/4″ in thickness (often called ″ “sheet metal”) are classified in the gage system. As shown in Figure 7-17, gages typically range from 4 (thickest) to 7 7 38 (thinnest). For example, 4-gage metal has a thickness of 0.2242″, a little less than 1/4″, ″ while 22-gage metal is ″ 0.0299″ (approximately 1/32″). ″ Steel manufacturer’s standard gage number Weight, psf Equivalent sheet thickness (in.) 4 4 6 6 8 8 1 10 1 12 1 14 1 16 1 18 2 20 2 22 2 24 2 26 2 28 3 30 3 32 3 34 3 36 3 38 9.375 50 8.125 50 6.875 50 5.625 50 4.375 50 3.125 50 2.500 00 2.000 00 1.500 00 1.250 00 1.000 00 0.750 00 0.625 50 0.500 00 0.406 62 5 0.343 37 5 0.281 12 5 0.250 00 0 0.2242 2 0.1943 3 0.16444 0.1345 5 0.1046 6 0.0747 7 0.0598 8 0.0478 8 0.0359 9 0.0299 9 0.0239 9 0.0179 9 0.0149 9 0.0120 0 0.0097 7 0.0082 2 0.0067 7 0.0060 0 Goodheart-Willcox Publisher Figure 7-17. Gages, weights, and thicknesses of sheet metal. Goodheart-Willcox Publisher Figure 7-18. Structural steel beams, columns, web joists, and other shapes are widely used in construction projects. These workers are installing a column onto a concrete footing.