the American Standard instructions say that the curled edges should be fastened to the studs and either drywall screws or roofing nails should be used. also the instructions say that because the nail/screw head will present a bump relative to the stud, a shim should be placed above it to make it even.
Q1: what would be a good shimming material that is thin enough ?
Q2: i am putting cement board over the walls. should i be using roofing nails or drywall screws or something else ?
Predrill through the fiberglass/acrylic lip and use hot dipped roofing nails, driving them just snug to the lip. I don't know why you have to shim "for the bump of the nail head". The thickness of the nail is nothing compared to the 1/4" lip of the tub unit. The two options are to stop the cement board at the top of the lip, then just fill in that little hollow spot behind the bottom 1/2" of the tile when you set it. or relieve the back of the cement board with a diamond blade so that it can fit over the thickness of the lip and nail tight to the studs. Either 2" hot galvanized roofing nails or the screws sold for cement board application will work ok. If you have finished walls on the back sides of the studs you are fastening to, I'd use the screws, as they offer a lot less chance of creating nail pops in the existing finish than banging all those nail in. I always run a small bead of silicone to seal the joint between the tub and the bottom of the backer board befor installing the finish. It is a cheap backup to stop moisture from wicking up the back side of the backer board. Keep the bottom row of tiles spaced 1/16" (wooden match sticks make perfect spacers for this) above the tub and caulk this joint, as grout will not last in the joint when the tub flexes.
Last edited by troubleseeker; 06-14-2008 at 08:34 PM.