Diagonal Bracing for Walls

See that angled board nailed to the vertical wall studs? It’s a temporary diagonal wall brace used to stabilize the framing while the house is built. © 2016 Tim Carter Builder

DEAR TIM: Yesterday I stopped by my new house that’s under construction. I go there at the end of each day to take photos. I saw a strange board nailed across the wall studs that surely is a mistake. It ran at a diagonal from the bottom wall plate up the wall to one corner of the wall.

I don’t see how the builder is going to install drywall over this. What’s it for and is it important? I was tempted to remove it thinking that the carpenters made a mistake. Would you install this board as you build a new home? Dan V., Austin, TX

DEAR DAN: I want to congratulate you on checking on the progress of your new home each day. That’s a smart idea. By doing this, you can catch errors and omissions in the construction process. Taking photos, thousands of them, is also very smart. Even though you have no idea what you’re taking a photo of, still do it. These photos can be very handy down the road should someone need to look at how your home was put together.

Years ago, it was expensive to take lots of photos. Now it’s nearly free because storing the digital information in the cloud or on other memory media is so simple. I’d also recommend that you start taking video and talk about what you see as you have the camera aimed at something. Take closeup shots of critical elements like plumbing connections, structural supports and beams, etc.

Holy potato! I’m sure glad you didn’t remove that temporary diagonal wall brace. You could have caused a wall to collapse hurting or killing someone, including yourself. My suggestion is to never touch one thing on the job site when you go visit. Things are done by carpenters and other workers for a reason. Believe me, no one wants to do extra work so if you see something that looks unusual, it’s best to talk to the builder or job superintendent.

When a carpenter builds a wood-framed wall using regular lumber and nails, the wall may be able to support lots of weight on its own, but the wall is not stable unless it has some form of bracing.

What would you say if I told you that a house could collapse if a gust of wind hit it? My guess is you’d say that’s hogwash because you don’t regularly see houses flattened after each windstorm in your town. But a house could easily collapse without some form of diagonal bracing in walls.

Here’s an easy way to prove it. If you are so inclined, take a few 2x4s and build a simple wall that’s 4 feet tall. Nail the studs every 16 inches on center like a real wall. Stand the wall up, nail the bottom plate to the floor and then go to one end or the other of the wall.

I want you to start to push on the top plate of the wall at either end. You’ll discover it doesn’t take much effort at all to make the wall start to fold down on itself. The top wall plate will remain parallel with the bottom plate, but the wall studs will start to all tilt at once as the top plate travels to the ground with you pushing it forward.

Straighten the wall back up making all the studs plumb and then nail another stud on the face of the vertical wall studs that’s at a diagonal from one bottom corner of the wall to the upper corner of the wall at the opposite end.

Now try to push the top plate and see what happens. No matter how hard you push, the top plate will not budge. The diagonal brace you saw at your job site was a temporary brace to keep a wall from moving. When I built I’d do this on interior walls that connected with an exterior wall. This braced wall would help prevent the exterior wall from blowing over as the house is being built.

You probably noticed the exterior walls of your new home have wood sheathing on them. It’s probably oriented strand board (OSB) or it may be plywood in rare instances.

Just one sheet of this material at each corner of a wall will provide the same bracing as the single piece of wood you saw on the other wall so long as the OSB or plywood is fastened to the wall studs with the correct nails in a distinct nailing pattern. The nails must not be over driven into the OSB or plywood. It’s best if the head of the nail is flush with the wood.

Years ago, carpenters would put in the diagonal brace you saw by mortising it into the wall studs. This is very time consuming but it gave the walls enormous strength. Metal T-shaped diagonal bracing can be put in walls that accomplishes the same goal. The carpenters set their saw depth so it cuts a kerf in each wall stud to accommodate the metal brace. If you ever see one of these braces in a wall, never ever cut into it.

Pay attention to the way the exterior OSB sheathing is applied to your home. If you want to download a helpful guide showing you how it should be done, just go to the APA - Engineered Wood Association online library for lots of great information. Here’s the URL: http://www.apawood.org/resource-library

This popular column was featured in the January 14, 2014 AsktheBuilder Newsletter.

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