First, let me say THANK YOU to everyone who helped out with my last project. I am incredibly proud of it and it couldn't have been done without this forum. I placed some nearly complete photos of the project up in the finished gallery. Problem is, my wife almost immediately wanted to redo the other bath after seeing how much she loved the one that was finished. Here we go again.

Background:
This bath has an alcove tub which was previously surrounded by plaster with tile over it. I believe it had failed and been partly retiled at some point. I am retaining some plaster in the room so I've got a lot of 1/4" shims up to get the plaster height (about 3/4" thick) to roughly equal the CBU height.

Problem:
Even with the shims on the studs, the CBU will fall on top of the alcove tub tabs and not lay in front of them. The alcove is retained from the old bath and is set. Here are the options as I see it right now.

1) Just let the CBU lay on top (not in front) of the alcove tabs and have the tiles (brick sized about 4x8) hang down over the tabs and use lots of thinset?? behind them to take up the extra space in front of the tab. The issue of the bottom tile concerns me but the wall will be straight.

2) Use a series of shims at the base or an extra stud nailed to each stud that angles slightly to let the CBU hang over the tab. This eliminates the issue with #1, but I add extra framing and the wall will have a slight bend.

Picture of the area in question (though the tub isn't flush on any of the 3 walls).


Also, is there anything I should place between the studs and the CBU?

Anyone? I fear I may have to ask this question at (sigh) DIY.

Option 2 is your best bet. You need to maintain a flat plane on the wall, so new studs attached to the sides of the existing is what I would do. In the corners and outside the front of the tub custom cut shim pieces to match the protrusion of the new studs.

Try to make the front edge of the new studs touch the back lip of the tub.
Plumb is not as important as maintaining a flat plane from corner to corner.

Big thanks (again) RC!!

What about the question of putting anything behind the CBU? I don't think I did on the last bathroom...just CBU taped with thinset and fiberglass mesh tape, then rolled it with a redguard type of compound. I've heard people say you should put down tar papar between the studs and CBU.

If you're using RedGard, there is no need for tarpaper or poly.

Consider sistering out the entire wall vs. your shims.

2x3 are good for this purpose, or 3/4 ply ripped down into strips. This will allow you to frame the wall out flush with the tub apron, eliminating any bowing of your CBU over it.
Your "new" wall can allow your CBU to be both plumb (regardless of what the wall is doing) and a flat plane corner to corner.
Also, you may want to consider adding more wood to either end of the alcove walls (if you have room). This will give you more space for bigger tiles down the front of the tub. Looks like what you've got may be a little narrow.

Thanks Guys!

I'm keeping some old plaster walls intact in the room, so that's why I did 1/4" shims so everything meets up there (the plaster is about 3/4" thick). I am concerned about how well bowing the CBU a bit will work, but RC's recommendation still sounds like my best option right now.


Option #1 above would be the easiest, but I don't know if it would work?? The bottom tile would be about 3/4 on CBU and 1/4 tiled directly to the tabs on the alcove with some . If I do this and redguard over the CBU down to the alcove tab...wouldn't this work?

Also, how do you get that old caulk off? I had a tough time with the razor blade.

Did I miss something?
Is there still some plaster on the tub surround walls?

I thought this was an alcove. If so there shouldn't be anywhere that needs to flush up to existing plaster unless all of it wasn't removed. The outside wall corners don't matter.

I always strip out all plaster as it's too inconsistant thickness wise to try and flush anything up to.

If you have an ACE hardware near you try and pick up some McKanica gel silicone remover.
You should also find similar products in Lowes or Home Depot paint departments.

BTW, always use plastic scrapers to remove caulking.