Tub Wall tiling help! [Archive] - Ceramic Tile Advice Forums - John Bridge Ceramic Tile


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02-03-2006, 09:34 AM
Hi all!

I'm remodeling our bathroom at my wife's request. She's 7 1/2 months pregnant, running around the house cleaning and changing everything(Including the bathroom). The midwives call it "Nesting," but it seems more like late-term pregnancy-induced psychosis to me. :crazy:

About the bathroom...
I'm doing it in two parts: Everything above the floor gets replaced first, then the actual floor gets replaced(More tile) after everything above it is finished. We're keeping our tub and toilet, and they're staying where they are(No plumbing changes!). The current tub surround is plastic, and we're replacing it with tile. We still have to use this bathroom(It's our only one) while it's being remodeled. Did I mention my two year old is learning potty training?(Swell timing.)

I'm still in the demo phase, so I haven't really committed to any flawed ways of putting tile up on this job yet. I've been lurking in this forum for a week, reading posts and Liberry articles, soaking up knowledge in preparation for this work.

That being said, I've still got a few questions that I could not adequately satisfy by reading others' posts.

1. Caulking for expansion joints. Where do you do this? In a 60X30 tub wall installation(three walls) how many joints would I need? How wide should they be? I read the liberry article, but I'm still a little confused. Somehow it seems like a really bad idea to have caulked corners of a shower tile job. In my best experience, caulk under those conditions fails after three years tops. Wouldnít grout hold up better, or would the whole wall be prone to failure? What specific brands and types of caulk would you use? Again, I read the liberry article on caulks, and couldnít tell whether the caulk at the store would live up to expectations.

2. Where should I use latex-modified thin set and when should I use unmodified thin set? Iíve done only one tile job(36 square feet, on a floor, 12Ē tiles, last August)), and I used TEC brand latex modified thinset. I still have half that bag. Is this the type of thinset Iíd want to use for a shower wall installation? My understanding of latex modified thin set is that it is simply less prone to cracking than unmodified thinset. If thatís true, why not use it everywhere?

3. Why is a .6 mil poly barrier suggested around a cbu-backed tub/shower. Isnít properly installed and taped CBU basically water-proof?

4. How would you recommend transitioning between the CBU and Greenboard? I have a 3 inch trim tile that will go around everything, and Iím wondering if the joint between the cement board and greenboard should be just slightly underneath that trim tile, just slightly outside where the tiling stops(Which would be a bear to tape I bet), or right at the point the tile stops. I realize this joint might have a tendency to be a weaker point of the wall, and I'm trying to figure out whether it would be best to try to "hide" it under the last tile, and risk having that tile fail, or to put it outside the tile and be forever dealing with cracks in the walboard. Also I read a post on this that referred to something called MasterBlend? What is it and where is it used? Should I be using thinset(Modified or regular?) on this joint if itís under the trim tile, and (drywall)setting compound if itís outside the tiled area?

5. What is Red Guard, and how important is it? Where do you get it, and under what types of circumstances would you use it?

6. Is there an accepted standard height for shower tiling that is not intended to go all the way to the ceiling? (Like one piece of CBU tall, installed vertically). Is there any reason not to install CBU vertically?

7. Why do the Yahoos at the big box stores still have jobs?! I was told by a tile schlepper at Menards that the best thing for tiled shower walls was premixed mastic tile adhesive. :bang: What a crock! Iím so glad I found this forum!

Thanks for your help,


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02-03-2006, 09:38 AM
i will try to answer most of your questions.

1. expansion joints in tub shower go at the corners 1/8 th inch and tub to cbu and tub to tile 1/8 inch.

2. yes modified the only time not to use modified has to do with certain membranes.

3.no it is no waterproof unless you redgard which is a waterproofing roll on membrane. works great i you do the redgard no need for polu byt poly is cheaper i like the redgard.

4. yes if you brak cbu and green under tile no fiishing is required.

5.look in number 3

6. 6 feet off floor is code where i live typically 60 inches minmum from tub.
no reason not to put vertically. i do it in showers all the time make sure to tape seams and fill with thinset not drywall mud.

7. when you dont give a crap about doing things correctly just the bottom line. :clap2: :goodpost:

02-03-2006, 12:42 PM

Thanks for the great response. I followed all of the responses except #4, the one reguarding the CBU to Green board joint. I understand that I should use thinset and tape on the joint, but are you saying that top border trim tile can be laid half and half on cbu and greenboard?

Also reguarding Red Guard - Does redguard diminish the adhesion of the thinset to the CBU? Does thinset stick to Redguard as well as it would to Cement board? Somehow the concept of Red Guard seems almost like putting a poly barrier between the CBU and the tile.

Thanks again for the response!


02-03-2006, 01:56 PM
yes it can i usaully cut the old drywall out at 59" above tub the tile to 64 or so. redgard is made from the same company who makes the thinset and cbu custombuildingproducts.com they offer a ten year warranty but the kicker is you have to use all their products in conjunction. n :clap2: o big deal they have good stuff. yes poly so to speak between thinset and cbu. i do it all the time regard is awesome stuff.

02-03-2006, 03:49 PM
Joel - RedGard is great. $37.00 a gallon (bucket) at Home Depot. Pricey but super stuff. No problems.

02-03-2006, 04:00 PM
So you roll on redgard on the entire surface of the CBU? In the picks of a lot of posts I've seen it only applied at the joins and edges.


02-03-2006, 04:29 PM
everywhere :crazy:

02-03-2006, 05:47 PM
Hi Joel, welcome. If you are going to use the redguard, you don't want to have any poly behind the cbu. Use cbu mesh tape and thinset/tape the joints and corners then roll your redgard on. You can use Versabond for thinset.

02-03-2006, 08:37 PM

I didn't know I was supposed to put a poly vapor barrier behind my CBU before I found this site. So, I redgarded my CBU - see pics below. NOT just joints. :)

It goes on pink and dries red. It is crazy stuff!!