What sheathing goes on a New Brunswick garage wall?

For a New Brunswick garage wall, the standard sheathing is 7/16-inch OSB (oriented strand board), though 1/2-inch plywood is the premium alternative — both are acceptable under the NB Building Code, and your choice comes down to budget, intended use, and how well the garage will be detailed against moisture.

Most garage builders in NB default to 7/16-inch OSB because it's cost-effective, widely available at local building supply stores, and performs well when it's protected by house wrap and cladding. A sheet of 7/16 OSB runs roughly $20-$35 in the current NB market, compared to $35-$55 for a comparable sheet of 3/4-inch plywood. For a 24x24 two-car garage, you're looking at 50-70 sheets of sheathing for the walls, so the cost difference adds up quickly.

Plywood vs. OSB in NB's climate is worth understanding before you decide. OSB is more sensitive to moisture than plywood — if it gets wet during construction and doesn't dry out before the cladding goes on, it can swell at the edges, delaminate, and lose structural integrity. In NB's wet Maritime climate, this is a real concern during the spring and fall building seasons when rain is frequent. If your project is moving quickly and the cladding will follow the sheathing within a few weeks, OSB is fine. If the garage will be exposed to weather for an extended period, plywood is more forgiving. Some NB contractors use OSB on the upper portions of walls and plywood on the bottom 4 feet where splash-back from rain and snowmelt is most aggressive.

Thickness and Structural Role

The sheathing on a garage wall isn't just a nailing surface for siding — it's a structural diaphragm that resists racking (the tendency of a framed wall to lean sideways under wind and snow loads). In NB, where wind uplift is a real consideration especially in coastal communities like Saint John and Shediac, proper sheathing nailing patterns matter. The NB Building Code requires sheathing nails at 150mm (6 inches) on centre at panel edges and 300mm (12 inches) in the field for standard applications. Your contractor should be following these schedules, not just nailing wherever is convenient.

For most garage walls framed at 16 inches on centre with 2x4 or 2x6 studs, 7/16-inch OSB or 1/2-inch plywood is structurally adequate. If you're building a larger garage — 30 feet wide or more — or a garage with a bonus room above, your contractor may specify 5/8-inch sheathing for additional rigidity.

House Wrap Is Non-Negotiable

Whatever sheathing you choose, it must be covered with a weather-resistive barrier (WRB) before siding goes on. In NB, Typar or Tyvek house wrap is the standard. This layer is what actually keeps bulk water out of your wall assembly — the sheathing alone is not waterproof. The house wrap should be lapped shingle-style (upper layers over lower layers), taped at seams, and carefully detailed around windows, doors, and corners. Skipping or rushing the house wrap installation is one of the more common mistakes on garage builds, and the consequences — rot in the sheathing and framing — don't show up until years later when they're expensive to fix.

One NB-specific detail worth mentioning: the bottom course of sheathing should stop about an inch above the concrete foundation or slab, with a pressure-treated sill plate between the sheathing and the concrete. OSB or plywood that sits directly on or near concrete will wick moisture and begin to deteriorate within a few years, regardless of how well the rest of the wall is detailed.

If you're planning a workshop or insulated heated garage, some builders in NB are moving toward rigid foam sheathing (like Rockwool Comfortboard or rigid EPS) as a continuous thermal break on the exterior, sometimes in combination with OSB. This adds cost but significantly reduces thermal bridging through the studs — worth considering if heating bills matter to you.

Need help finding a garage builder in your area? New Brunswick Garages can match you with local contractors for free — browse the directory at newbrunswickconstructionnetwork.com.