All building codes require that walls be braced to resist racking caused by wind loads (see illustration below.) Most prescriptive codes recommend one of three options: 1x4 diagonal bracing, 5/8-inch diagonal board sheathing, or 3/8-inch plywood sheathing. Other more progressive performance-based codes specify minimum design values for racking resistance, but let you achieve them with almost any materials you choose. For example, you can count the combined contributions of metal strapping, drywall, interior partitions, and ceiling diaphragms. Some foam sheathing manufacturers point to these performancebased measures as proof that a foam-sheathed wall meets code. It's true that with the right floor plan, wall dimensions, and number of wall openings, an unsheathed or foam-sheathed wall might comply with code. But bear in mind that most code officials
