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Wall sheathing – vertical or horizontal

Our inspectors had an interesting discussion the last little while over an issue that apparently is common.

An area contractor asked if OSB sheathing could be installed vertically (in a braced wall panel) instead of horizontally.

The question led to an interesting dive through the Code books, standards, manufacturing requirements and the like.

First off, there are requirements in Code that OSB and similar sheathing materials is installed perpendicular to joists or roofing systems (rafters/trusses), and frankly, this is almost never an issue as far as framing inspections go. Most contractors install OSB wall sheathing horizontally, presuming the same factors are in play as for roofs and floors. However, after much digging, it turns out that there are no requirements to do so. That said, OSB has greater strength on its long axis, and best practice says to install it horizontally.

So, while we’re on the issue, here’s a quick thought: if you’re installing OSB or plywood as sheathing material, do you leave a gap? You’re required to – 2 mm by Code, in fact. [,]