Figure 1-52.—Chase wall construction.

Figure 1-52.—Chase wall construction. buildings are framed in a combination of metal and wood. The metal framing members generally used are cold-formed steel, electrogalvanized to resist corrosion. Thicknesses range from 18 gauge to 25 gauge, the latter being most common. Most metal studs have notches at each end and knockouts located about 24 inches OC (fig. 1-51) to facilitate pipe and conduit installation. the size of the knockout, not the size of the stud, determines the maximum size of pipe or other material that can be passed through horizontally. Chase (or double stud) walls (fig. 1-52) are often used when large pipes, ducts, or other items must pass vertically or horizontally in the walls. Studs are generally available in thicknesses of 1 5/8, 2 1/2, 3 5/8, 4, and 6 inches. The metal runners used are also 25-gauge (or specified gauge) steel or aluminum, sized to complement the studs. Both products have features advantageous to light-frame construction. The metal studs and runners do not shrink swell, twist, or warp. Termites cannot affect them, nor are they susceptible to dry rot. Also, when combined with proper covering material, they have a high fire-resistance rating. A variety of systems have been developed by manufacturers to meet various requirements of attachment, sound control, and fire resistance. Many of the systems are designed for ease in erection, yet they are still remountable for revising room arrangements. The framing members are assembled with power screwdrivers and using self-drilling, self-tapping screws. The floor assembly is fastened to the foundation or concrete slab with studs (special nails) driven through the stud track (runner) by a powder-actuated stud driver. The plywood subfloor is installed over the metal floor framing system with self-drilling, self-tapping screws and structural adhesive. Wall sections are assembled at the jobsite or delivered as preassembled panels from an off-site prefabrication shop. Conventional sheathing is attached to the framework with self-tapping screws. Door frames for both the interior partitions and exterior walls are integral with the system. They are preprinted and may come complete with necessary 1-31