Wood Structural Panel Opening Protection Takeoff

ScopeBefore a hurricane every hardware store sells out of plywood, and the IRC R301.2.1.2 exception for wood structural panel opening protection sets the rules: plywood or OSB at least 7/16 in thick, spanning no more than 8 ft, precut, predrilled, and fastened to the framing around the opening by a schedule tied to the span. The panel is the opening plus an overlap on every side; the span is the distance between the two fastened edges; and the fasteners run along each fastened edge at the spacing the adopted table gives for that span. The table is ICC text, so the spacing is entered and the calculator names which span column to read. A 36 x 60 in window with 4 in of overlap is a 44 x 68 in panel, one 4 x 8 sheet; fastened along the 68 in sides it spans 44 in (3.67 ft), and at a 16 in spacing with 1 in edge distance it takes 6 fasteners per edge, 12 per panel. Fastening the short sides instead makes the span 68 in, 5.67 ft, which moves the panel into the 4 to 6 ft column and a closer spacing -- the usual reason to fasten the long sides. Thicknesses under 7/16 in and spans over 8 ft are refused with the code limit, and a panel larger than a sheet is flagged for the splice the exception does not provide. In the 2018 IRC the table is limited to a 45 ft mean roof height and 180 mph ultimate wind speed. It does not check framing or embedment, address doors, garage doors, or skylights, or replace tested products where required. The adopted IRC and the AHJ govern.

Formula or tablepanel = opening + 2 x overlap each way; span = dimension between the fastened edges (<= 8 ft); thickness >= 7/16 in; fasteners per edge = ceil((edge length - 2 x edge distance) / spacing) + 1, x 2 edges; sheets by nesting onto 4 x 8 ft stock; spacing entered from the adopted Table R301.2.1.2 column for the span.

Source and editionIRC Section R301.2.1.2 and its exception for wood structural panels, and Table R301.2.1.2 (2018 edition limited to a 45 ft mean roof height and 180 mph Vult), cited by section; the fastening schedule is NOT reproduced. The adopted IRC and the AHJ govern.

Free accessThe IRC is cited by section only; the fastener spacing is a user input read from the adopted edition's table.

What governsEstimate. AHJ and licensed professional govern.

API field namesopening_width_in, opening_height_in, overlap_in, thickness_in, fastened_edges, fastener_type, fastener_spacing_in, edge_distance_in, opening_count, panel_width_in, panel_height_in, span_in, span_ft, fasteners_per_edge, fasteners_per_panel, sheets

• Panel minimums wood structural panel at least 7/16 in thick, span not over 8 ftIRC R301.2.1.2 exception
• Fastener spacing entered from the adopted Table R301.2.1.2 for the fastener type and spanuser input
• Sheet stock identical panels nested onto 48 x 96 in sheets, no splicingtile method