Q. Stiffening a Pony Wall for Tile
I’m framing a new slab-on-grade home where the master shower is enclosed by a pair of 6-foot-tall pony walls that are connected to the flanking walls only at their ends. Because both partitions will be covered with ceramic tile, I’m wondering how I can frame a wall rigid enough to prevent cracks.
A.Robert Zschoche, a tile-setter in Chantilly, Va., responds: I was faced with a similar situation in the second-floor bathroom of a recent remodel (see illustration, below). I used upside-down joist hangers to fasten double 2x6 blocking between the floor joists directly under the freestanding end of the wall, then ran a length of 5/8-inch threaded rod through the wall plates and blocking, with a square piece of 1/4-inch steel under the blocking and a heavy fender washer at the top to distribute the pressure on the wood as I tightened the nuts. For added stiffness, I glued and screwed some 1/2-inch plywood to the back of the wall. I used Wedi board tile backer on the side facing the tub. Once I’d cranked down on the top nut, the wall felt stiff enough to convince me it wasn’t going anywhere; that was several years ago and there have been no problems with the tile since.
On a slab, I’d use that same approach, but would anchor the threaded rod to the concrete with an epoxy capsule. Ideally, an engineer would spec this sort of detail, but in my experience — probably because there’s no life-safety issue — the solution is left up to the contractor.