Tile Wainscot and Tub Surround

Hello to all!!

I'm in the process of redoing a bathroom. I want to replicate the "mud" job look with cove molding and mud cap.

On the wainscot my approach is to apply wonder board at 41" hgt over existing wall and tile over that. In the tub area I can pop off the existing 4x4 tiles circa 1970 and the thought is to apply wonder board over existing sheet rock in this area to continue the wainscot surface into the tub area with the same mud cap.

Plan is to thinset the wonder board to all existing wall surfaces - screw into all joists @ 6"c/c.

Not being an expert, will this approach prove successful?

The existing tub area sheet rock, though old, is in sound condition. Would a layer of plastic sheeting be advised under wonder board in this area?

Will the mud cap install correctly??? K_C

Is the tub also used as a shower? If so, you're lucky the drywall isn't in bad shape. If it isn't used as a shower, then yes, your plan should work. Leave the cbu a little bit off the top of the tub and caulk it. When installing over the drywall, you'll need longer screws than normal to catch the studs...no real benefit to screwing to the drywall inbetween - you'll find it hard to figure out when to stop since the cbu is so much denser. The only time you use thinset under cbu (or at least the only time it is needed) is if it is a floor, and then, it is necessary for a reliable install. You'll get some good info on tiling at www.johnbridge.com.

jadnashua,
Thanks, I found John Bridge while searching this forum after I posted. Already there with answers.

You guys rock! Nice to be able to get quick answers and sound advice.

Do you think the thinset under the backer will aid in moisture control? I'll be using 4x6 tiles. K_C

Nope, thinset under it won't do anything useful on a wall...just screw it to the studs. A waterproofing coating wouldn't hurt - Kerdi, or Redgard.