WATERPROOFING I always approach "waterproof- ing" the same way. Namely, there is really no such thing. Instead, I make sure water that does eventually get in can then find a way out. And even though it's dry behind the wall (I left the framing open inside a closet so I could monitor this), there is always some calamity that may ensue, like—and I kid you not—my son fig- uring out that the faucet can spray really, really far. He thinks this is hilarious. So the first thing I did was coat the backs of the Yellow Pine 1x4 T&G beaded boards with one coat of Spar urethane. It’s enough to keep the back from holding moisture. Next, I detailed the corners with roofing membrane. Where water
The DPM creates an air gap that facilitates drainage and ventilation of any water vapor that gets behind the shower panels. Any time you install a sheet product, it’s impor- tant to get the membrane taught and flat, otherwise lumps and bumps and ripples will chase you around. Washer-head screws work better than drywall screws here.
A layer of Dam Proofing Membrane (DPM) covers the roofing mem- brane and framing.