Flooring Tile - backer board/tub surround

I'm installing new tile tub surround with an older tub. The old tile and drywall are removed down to the studs. I'm preparing to install the cement backer board, but a little confused about exactly how close to the tub the cement board should come. This tub has a 3/4 in. flange that comes up from the surface of the tub and rests against the studs. There are also some metal straps that attatch to the studs. Should the backer board come down to the top of the flange with the tiles then extending further to the surface of the tub? Or, should I shim the studs so that the backerboard can come down and cover the flange and rest 1/4 in. from the surface of the tub (caulking the 1/4 inch with silicon)? Or something different? Thanks much!!

Sue

Hi Sue,

The backer board should stop just a hair above the lip or flange (an eighth inch or so). The space is then filled with silicone caulking. The tiles will then go down and rest on the tub deck.

I'm a mud man, and I don't use backer board, but if I did, I would install it differently. (I usually get in trouble over this issue, but . . . )

Install greenboard/sheetrock onto the studs. Then install a moisture barrier -- poly or craft paper. Then install the backer board cut precisely to fit the tiles and the bull nose.

What you end up with is a job that looks like it was done on lath and mortar (mud). The bullnose you use is called mud cap or radius bullnose, and it is identified by a universal part number: A-4200.

The sheetrock behind the backer stiffens it up, although others will argue it's stiff enough already.

I'll just stand back now and prepare to dodge flying objects.

John :-)

http://www.johnbridge.com

Hi John,

Thanks for the information...I promise I won't throw anything!

A follow-up question...

So, the backer board will then end up being nearly 1 inch above the surface of the tub, and the tile will then come down to the surface of the tub (really the surface? or leave enough space for silicon caulk?). I'm assuming that I would need to be a little careful (especially with grouting) with that lowest line of tile, since the lowest portion of the tile will be just "hanging"...that is...no backer board behind it. And, this is okay? Just want to be sure!!

Sue

Hi Sue,

I love these quick exchanges. Reminds me of my aol days -- instant messages, etc.

Again, I don't do it myself, but that's how it's done. The tiles hang down. Don't worry about the grout. It'll hold. And at the very bottom you will need to caulk. But that would be the case no matter what, because grout doesn't like to stick to the tub itself.

But, you see, if you had sheetrock on the wall, well,then the backer could come down almost all the way to the tub deck (leave an eighth inch for caulking), and the tiles would be supported all the way, but here we go again, eh?

And Sue, I'm not worried about you throwing anything. It's other pros who deal with backer board a lot more than I do, and it's the "tile police."

John :-)

John,

Thanks for the quick responses! Can you tell I want I get started on this tomorrow??

I very much appreciate the advice. Stay clear of the tile police!

Sue

Hi Sue,
Personally I shim the studs with a 1/8" lattice strip and go over the flange But, to each there own. Both ways are acceptable practices and no matter what you do make sure that you install some type of water barrier between the studs and backer board and/or the drywall and backer board.
That I think is far more important than anything else.
Regards,

Rich Gately (Tileman1)

http://www.gatelytile.com

Hi Rich,

I thought about furring the studs out a little, but then how do you make the transition back to the sheetrock at the edges? Is there a slight bow, or what? Or maybe you just shim out down near the tub and leave the wall a little out?

John

Hi Rich,

Thanks for chiming in. Yes, I'd read about the water barrier. Is it really necessary behind 1/2 inch of cement board? It seems an easy thing to do, though. Would I just use a heavy plastic stapled to the studs?

Oh yes, I'd have the same question as John's last question.

Thanks,
Sue

Hi all,
I usually furr out the entire stud to the ceiling Unless of course its like vaulted or something then I figure something else out as I go. :D (A little mud at the lip for support under the bottom course)
The reason I use a vapor barrier is cement board likes to wick moisture its not as prevelent on tub surrounds as in showers but, it only takes 5 minutes before you put up backer board and yes I staple it to the studs.
OOOOOH!! you mean at the side walls, correct? I will usually fill that 1/8" with caulk, duradond 90 or drywall compound. My main concern is supporting that bottom course at the tub flange and to prevent leaking. As I write this I basically have this scenario going on right now on a job and I'm going to try it and let you know how it turns out. Gotta go!
Regards,

Rich Gately (Tileman1)

http://www.gatelytile.com