Wood, metal and plywood can all be used to keep walls from racking.
Synopsis: This framing lesson from Larry Haun deals with reinforcing rough-framed walls with bracing so they won’t rack out of square. He shows how let-in bracing, plywood, and metal hardware all can be put to use. A sidebar discusses the use of shear walls in areas prone to earthquakes.
I was born and raised in rural Nebraska, where the one constant is the wind. Many of the farm buildings I remember from my childhood leaned to one side. I was fascinated by these buildings. I used to think that was the way people built them. It took a while to figure out that those buildings leaned because the wind was always pushing on their poorly braced walls.
The first house I helped build was in 1947, back in the handsaw days. For wall bracing we mitered the ends of 2×4 blocks, then we nailed the blocks between studs along a diagonal line — good braces to prevent racking but time-consuming to build.
I now live and work on the West Coast, where houses must be built to withstand not only the wind but also earthquakes. I’ve braced many a wall, and here I’ll talk about the best ways I’ve found to keep walls plumb and true through gusts and tremors.
Once platform framing became popular, carpenters learned to brace walls by mortising, or letting in, a diagonal 1×4 or 1×6 into the plates and the studs of a wall. Many building codes call for this type of bracing in almost every wall that has room for it. Braces are required at each end of a long wall, with an additional brace for every 25 ft. of wall space. The codes don’t say how long the braces should be; they just say you must have them. Each brace must oppose the other — one slanting one way, the next slanting the opposite way — to guarantee that one member will always be in compression (the force that pushes together or crushes). Let-in wood bracing works best in compression.
I like to use let-in bracing even if the wall will later be sheathed with plywood (another form of bracing). It takes me only two or three minutes to install a brace, and let-in bracing holds the building plumb until the sheathing goes on. Other carpenters sheathe their walls before raising them or hold walls plumb with temporary 2×4 braces after they’re up. But sheathing the walls first means squaring them up perfectly on the deck — a tedious job — and when temporary braces get in the way, workers tend to remove them: there go the plumbed and squared walls.
When shear forces go beyond the ordinary, a structural engineer can calculate how to brace a wall to keep it from racking and uplifting. Often, it’s a matter of combining panels and seismic anchors. But where high winds or major earthquakes are uncommon, 1xs are adequate for bracing. For the inexperienced, installing 1x let-in bracing can be dangerous, so the procedure needs to be studied well and executed carefully to avoid injury.
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