cement board installation around tub with mounting flange

[ESM]

After reading a few articles online and asking a few people, as well as reading the instruction that came with my tub (Sterling made), it said that the cementboard should be installed in FRONT of the tub flange and leave about 1/4" gap. Well, I took this route and you can see my part way through below:



After reading a few post on here, everyone seems to say that if you are going to do this, you should put up furring strips so the backerboard doesn't bow. The flange on this tub ia bout 1/8" thick and there is some slight bowing because of this. I really didn't think much of it at the time. Other people say to just sit the board on TOP of the flange and fill the base in with some form of thin/thickset.

Well I have no the right side wall and the entire backwall up, over the flange, with a slight bow. I have 1 more wall left to do, which is the left side.

How critical is it that I either cut out the base of the boards (essentially making the board rest on top of the flange). I'm really not looking forward to having to take the piece down to be honest, so I'd just grab my dremel and do it on the wall.

Could a decent tile person just deal with it as? I plan to use a standard 4" square tile. This is a guest bath with little use. It will get used for actual bathing, and only used as a shower a handful of time a year. Is my only concert tile fitment, or is there other concerns?

[Jason_Butler]

Let's back up a minute..

I don't see any vapor barrier over those studs. Although it is not as critical for the tub surrounds as for showers, lets do it right before you get too far along.

There is no functional degradation with leaving that CBU the way it is BUT your early in the project and sonce you are gonna' take down the CBU to put in the vapor barrier, might as well trim some off the bottom of the CBU. Rest it on the flange and let the tile overhang a bit.

Jason

[Raymond S]

Yeah, you need to do it like Jason said. Had you had a vapor barrier up, you could have probably cut off the cbu to go above the tub lip, but you wouldn't have liked the finished product with that bow in the wall if you didn't trim it, you WOULD notice it every time you went in the bath.

[LonnythePlumber]

Doesn't look like the hole for your faucet is big enough for you to even install the escutcheons screws. You are supposed to leave the 5" or so plaster guard on, so you know you have the valve set the right distance in and out and so there is room left to replace the valve later. You should at least make sure your escutcheon will sit flat and not have a wall indentation that requires a bigger hole.
I shim and let the CBU go down past the flange. I don't like a seam at the top edge of the tub as you have installed. Often it is the first area to fail.

[cx]

Welcome, ESM, wassa you name?

Yep, what all them others said. Gotta do it.

How's come you ain't doin' the tile yourownself? That's the fun part.

[ESM]

I test fit the depth after holding the CBU up temporarily and everything looked good. I did realize after securing the CBU I couldn't get at the holes to mount the trim plate, but I'm going to open up the board some more with my dremel.

I guess I'll take down the lower pieces and cut them short the distance for the tub flange. Not having to deal with the bow when tile gets done will just save some potential headaches I suppose.

Evan

[cx]

How about the moisture barrier, Evan?

[ESM]

Originally Posted by cx

How about the moisture barrier, Evan?

Well.. that seems to be a popular theme in this thread! There was no moisture barrier when I took down the old walls, which were put in about 3 years ago now, I had to redo this because the drain pipe for the tub broke and flooded the bathroom, so I decided to redo it all, tub was ivory anyway and we wanted white. So I didn't think of putting up anything. The old walls were 1 sheet of 1/2" greenboard and then 1 sheet of 1/2" cement board. I'm doing 2 sheets of 1/2" cement board however. Costs a little extra ,but what the heck.

Is moisture barrier still going to be a necessity with 2 sheets of 1/2" cement board? If so, what do I buy? I'll go down to Lowes/HD to pick it up.

[opiethetileman]

15 lb roofing paper works very well. YOU NEED THE mositure barrier. Whats a few extra dollars and a few extra minutes of work.