Sheathing
Affiliate link — we may earn a commissionSheathing is the layer of sheet material fastened to the outside of wall studs or the top of floor joists. Wall sheathing is usually 7/16-inch or 1/2-inch OSB (oriented strand board) or plywood. It stiffens the wall against racking (sideways forces from wind or earthquake) and provides a nailing surface for siding. Floor sheathing (subfloor) is typically 3/4-inch tongue-and-groove plywood or OSB, screwed and glued to the joists. Roof sheathing is similar to wall sheathing, fastened to rafters or trusses. You cut sheathing with a circular saw and fasten it with a framing nailer or screws.
Why It Matters
Sheathing is the surface you work on and through during most residential construction. When you're nailing siding, you're nailing through sheathing. When you're cutting a hole for a dryer vent, you're cutting through sheathing. Knowing what's behind the sheathing (studs, joists, wiring, plumbing) matters before you cut or fasten.