Effective wind area for the design of roof sheathing under wind loading
Abstract
Wood-frame structures are a popular choice for construction in North America. Due to their sensitivity to severe wind events, the design of these structures under wind loading is of particular importance. One of the issues with wind loading on cladding elements like roof sheathing is the determination of the “effective wind area” to use in design since the design pressure coefficients decrease logarithmically with area. The current design approach for cladding uses a geometric tributary area approach to calculate the wind loads and determine adequate fastening schedules. This fails to include load sharing and design pressure coefficients may be excessively cautious. The objective of the current work is to determine the effective wind area of a roof sheathing panel under three fastening schedules: 6 in by 12 in, 6 in by 6 in, and 3 in by 3 in. It was found that the effective wind area of a 7/16 in oriented strand board sheathing panel was about 24 sq ft regardless of fastening schedule. This value contrasts with the tributary areas of 2 sq ft, 1 sq ft, and 0.5 sq ft, respectively for the three schedules. However, using the full sheathing panel area of 32 sq ft would be slightly unconservative.