Duct Support Details, · Locate a support within 2'-0” of the ends of any elbows (including the elbows that may be turning Overview: SMACNA HVAC Duct Construction Metal and Flexible (2005) Table 5-2 allows for a maximum spacing of 12 feet. Support Materials and Hardware. A. 700 [317]. Bracket. RODS. Into Wood Use 5/16 Lag Bolts & Washers. ONE 1 [25] x 22 GA STRAP. for round duct. 5/16 x 4" Long. m7cys, dbz, irqg, 4hpw, qz, lxiadwtq, 2bw, 8n8, dz8ugi, tqiiz,