Which Of The Osb’S Sides Faces Outside?

OSB (Oriented Strand Board) panels have both rough and smooth sides. When installing OSB as wall sheathing, the smooth side faces out due to its better moisture resistance. However, on roofs, one side is not as smooth and is better for walking on. Inspectors often prefer the grade stamp on the bottom, but it doesn’t matter structurally.

OSB is installed vertically over the entire exterior of a home, with the first panel installed at the side of the home, flush with the corner of the building and the bottom edge flush with the sill. The remaining sheets are set at the top and gapped 1/8″ at the sides. The rough side is pressed in on purpose using a screen caul on one side and a flat steel plate caul on the other.

When installing OSB on roofs, the rough side should face up, as the smooth side has a wax coating that sheds water more effectively. The coated side of the board should always face outward to ensure better protection from the elements. When used as subflooring, the coated side should be facing down against the joists. When used as wall sheathing, the coated side should face outward.

When installing OSB horizontally, the rough side faces out, with red lines 16oc. Platform framing the wall also uses the rough side out. Painting OSB is easier on the smoother side, especially if brushing the paint on. There is no “right way” in applying OSB, but the choice depends on whether you prefer a rougher texture or not.