Hardwood Floor Installation Over 24" o/c Joist

Can hardwood flooring be installed on floor systems with 24" o.c. joist spacing?

The National Wood Flooring Association (NWFA) has become the leading organization for wood flooring certification and the predominant source for proper installation of wood flooring. The NWFA Installation Guidelines provide information on proper acclimation, subfloor guidelines and specifications, and installation guidelines.

Although 23/32" OSB is span-rated for floor joist systems spaced at 24" on-center, NWFA believes a thicker subfloor is necessary to reduce deflection of the subfloor and minimize pops and squeaks in the wood flooring. Therefore, the NWFA
recommendation is to use a 7/8" thick OSB panel for floor systems spaced at 24" on-center.


NWFA Recommendations

Chapter 4 – Wood Subfloor Guidelines, Part IV – Panel Products Subflooring, Section E – Acceptable Panel Subfloorsprovides minimum acceptable thicknesses of panel subflooring, depending on the spacing of the floor joists. Item 3

“Truss/joist systems spaced over more than 19.2" o.c. up to a maximum of 24" require minimum ⅞" T&G CD EXPOSURE 1 Plywood subfloor panels, 4' x 8' sheets, glued and mechanically fastened, or minimum 7/8" OSB Exposure1 subfloor panels, 4' x 8' sheets, glued and mechanically fastened – or two layers of subflooring. Or brace between truss/joist in accordance with the truss/joist manufacturer’s recommendations and with local building codes. Some truss/joist systems cannot be cross-braced and still maintain stability.”


Edge Gold™ Code Conformance and Availability

Edge Gold™ floor panels are manufactured in accordance with Voluntary Product Standard PS2 and CAN/CSA-0325 with an Exposure 1 bond classification. 7/8" Edge Gold™ floor panels are available through Weyerhaeuser Wood Product Dealers and Independent Distributors.

For more information, refer to the Weyerhaeuser Technical Bulletin TB-928 and OSB -4021(7/8").
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