yes it is 100 percent water proof and you use dry wall screws or galvanized nails to attach to 2 x 4 studs, then you fill seems and corners with the same glue as you do to install tile to walls. all water proof.and when I pak my shower floor the vinyl shower pan material goes on first, up the wall aprox 8 inchs and nailed to studs and down the drain then durrock goes over that. pak floor with portland cement and white sand and you have a water tight shower. I always build my showers this way.