Roof curbs shall be, pre-fabricated of AZ55 Galvalume steel, minimum 18 gauge. Construction shall conform to commercial quality specifications, with fully mitered and welded corners, and shall include a formed-in integral water diverter. All welds shall be continuous, and shall be coated with one coat of aluminum colored urethane sealer. Curbs shall be internally reinforced, factory insulated, with 1 1/2” thick 3 lb. density fiberglass insulation. Height shall be a minimum of 8” above the plane of the roof panel or as detailed. Top of all curbs for roof top equipment shall be level, with pitch built into curbs. Curbs for roof hatches, skylights, and smoke hatches shall be constant height curbs following pitch of the roof unless specified otherwise. All curb flanges shall be pre-punched at 3” max centers with 1/4” holes, 1” in from outside edge of flanges.