166 April 2021 LUMBER & MILLWORK FAMILY OWNED & OPERATED SINCE 1946 B U I L D E R T I P S Cut Callbacks with Proper Spacing Spacing Recommendations for APA Rated Sheathing, APA Rated Sturd-I-Floor ® , and APA Rated Siding. Wood structural panels (plywood and OSB), like all wood products, will expand or shrink slightly with changes in moisture content. If expansion is prevented by tightly butted panel joints, buckling can occur. And that can mean costly, time-consuming callbacks. To assure best performance, follow these panel spacing and nailing recommendations. Spacing Hint. A 10d box nail may be used to gauge 1/8-inch spacing between panels. Spacer-type panel edge clips may also be used for roof sheathing applications. NOTES: Panel spacing is an APA RECOMMENDATION, to provide installers with a means of minimizing the potential for panel buckling; however, it is not a requirement. Some manufacturers may require a space at the time of installation. Panel buckling may be an aesthetic or serviceability issue but is not a structural deficiency. There is no reason to expect this recommended space to be maintained when the panel becomes acclimated. Gaps that were initially present may have closed due to normal moisture-related expansion. If the flatness of sheathing or flooring panels is acceptable, APA would generally recommend that any finish flooring, siding or roofing be installed as planned regardless of whether gaps are present. Edge Joints: 1/8" spacing is recommended at all panel edge joints unless otherwise recommended by the manufacturer. In Glued Floor Systems, use adhesives conforming with AFG-01 or ASTM D3498. * T&G profiles and installation recommendations can vary among APA members. Check with individual manufacturer for specific recommendations – otherwise, APA recommends 1/8" spacing at all panel edges. 1/8" space Approximately 1/16" space EXAMPLES OF TONGUE-AND-GROOVE (T&G) JOINTS* End Joints: 1/8" spacing is recommended at all panel end joints unless other- wise recommended by the manufacturer.