All About Tongue and Groove Wall Sheathing

A modern building envelope has several layers of thermal, air, vapor, and water protection. Siding is the first layer of defence, although we wouldn’t dream of installing this at a home without proper insulation in place.

You see, siding adds an attractive exterior finish to any home, but it is never 100% effective when it comes to air, temperature and moisture protection. So what did people do about this problem when all they had was timber?

We still come across timber tongue and groove wall sheathing in older North American timber frame homes. We need to get a grip on what wall sheathing does, to fully understand why people did this.

tongue and groove wall sheathing
Historic Tongue and Groove Weatherboard in Philadelphia (HABS BY Public Domain)

Wall Sheathing Plays Several Roles

Wall sheathing encloses and protects the underlying structure. But if the sheathing is timber or another solid material, it also reinforces the underlying structure.

Nowadays, the preferred material is plywood, orientated strand board, or gypsum. This solution is popular in high-wind areas, where there is a possibility of gusts getting behind the siding and peeling it away.

Tongue and groove wall sheathing is available in softwood and plywood in most timber stores. This dates from before the days of plywood, and was the generally accepted method for weather-proofing buildings back then.

tongue and groove wall sheathing
Installation of Modern Tongue and Groove Material (Oleg Bor BY CC 4.0 Share Alike)

Modern Options for Building Wall Sheathing

There are two ways to fit wall sheathing to an underlying structure. The first of these involves abutting the sections against each other and allowing a small gap for expansion, caulked with flexible sealer.

Various materials are available to do so, including oriented strand board, structural fiber board, plywood, foam board, and gypsum.

However, there are several advantages to the alternative, tongue and groove, that compensate for installation taking longer and therefore being more expensive:

  • The effect of wood shrinkage is less obvious in dry weather.
  • The joint is more rigid. It helps stabilise the underlying structure.

Tricks of Trade With Tongue and Groove Sheathing

Horizontal tongue and groove sheathing should be installed with the groove on the top edge of the boards, to encourage surface water run off. Installing the boards vertically or diagonally provides even better drainage, especially if the sheathing is left exposed. Contact Valiant Exteriors in Calgary for more information at (403)829-1661.

More Information

Blind Nailing Versus Face Nailing Siding

Butt Joint Flashing for Fiber Siding

Diagonal Tongue and Groove Wall Sheathing by Valiant Exteriors©