Figure 1: Oriented Strand Board

OSB Frequently Asked Questions

Q How do I install OSB as floor sheathing?

A Select the correct thickness or span rating for the application as per local building code requirements, either a single layer combination subfloor/underlayment or a subfloor to be covered with underlayment, hardwood flooring, or light weight concrete.

Lay panels across three or more supports, keeping the side marked "This Side Down" on the supports when using T&G panels. End joints must be made over the supports and should be staggered at least two supports.

Lightly butt tongue and groove panel sides together and leave 1/8" (3 mm) gap at panel ends. Panel ends of single layer combination subfloor/underlayment should be lightly butted.

Use 2" (50 mm) or 6d deformed shank nails, 1-3/4" (45 mm) No. 10 screws or 2-1/2" (63 mm) or 8d common nails at 6" (150 mm) o.c. along panel edges keeping fasteners 3/8" (10 mm) away from panel edges. (Drywall screws are not recommended.) Space fasteners at 10" (250 mm) o.c. on intermediate supports for single layer floors and 12" (300 mm) o.c. for subfloors. (Special instructions for fastening glued and nailed subfloors are available from manufacturers or the Structural Board Association.)

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