Installing shower tile question

[TresK3]

The never-ending bathroom remodel may actually be approaching completion! I'm finally tiling the shower.

I tiled the floor of the shower with a flat, natural stone mosaic. Now I'm doing the side walls with a 9x12 white tile, laid in a brick pattern. Because the bottom tile is stone, it doesn't give a perfectly smooth surface for the wall tile to land on. There's a small gap between the wall and floor tile (about a 1/16", depending on the height of the stone). Now I'm wondering what to fill this space with? I could squeeze grout into this joint between the wall and the floor or use a high quality silicone caulk. I'm leaning towards the caulk because it can flex a little, but I'm worried about how long it will last.

If it matters, the foot of the shower is on an outside wall, the back (long side) is against an unheated attic, and the head of the shower is along a closet.

Thanks for any thoughts, suggestions, ideas or experience with this.

 

[Wooden Head]

The never-ending bathroom remodel may actually be approaching completion! I'm finally tiling the shower.

I tiled the floor of the shower with a flat, natural stone mosaic. Now I'm doing the side walls with a 9x12 white tile, laid in a brick pattern. Because the bottom tile is stone, it doesn't give a perfectly smooth surface for the wall tile to land on. There's a small gap between the wall and floor tile (about a 1/16", depending on the height of the stone). Now I'm wondering what to fill this space with? I could squeeze grout into this joint between the wall and the floor or use a high quality silicone caulk. I'm leaning towards the caulk because it can flex a little, but I'm worried about how long it will last.

If it matters, the foot of the shower is on an outside wall, the back (long side) is against an unheated attic, and the head of the shower is along a closet.

Thanks for any thoughts, suggestions, ideas or experience with this.

A couple of questions.
What have you used for backer for the tile?
What have you used for waterproofing the backer?
What is flexing and why?

 

[TresK3]

A couple of questions.
What have you used for backer for the tile?
What have you used for waterproofing the backer?
What is flexing and why?

The backer is cement board. I don't remember the brand - it was either Durock or Permabase (I've used both at times). The shower base is a KBRS one piece unit. I used the KBRS polyurethane caulk at the joint between the cement board and the shower base, but it set up much faster than I expected and wasn't as smooth as I would have liked. I also filled the cement board joints with "tape" and modified thinset (and covered the screw holes with thinset). Then I covered all seams and joints with KBRS gauging fabric, as per KBRS instructions. Finally, I coated the whole thing (walls and floors) with at least two coats of KBRS "liquid liner" (three coats on the corner & side joints).

As for flexing, I'm concerned that because of temperature and material differences the sides and floor will expand and contract at slightly different rates. If I use something like grout, this might crack. A silicone caulk should absorb those slight changes without cracking... I think.

Thanks!

 

[gzecc]

Caulk that matches the grout. Caulk should be used in the corners where walls and floors meet. Caulk will expand and contract with movement,, grout will not.

 

[Wooden Head]

The backer is cement board. I don't remember the brand - it was either Durock or Permabase (I've used both at times). The shower base is a KBRS one piece unit. I used the KBRS polyurethane caulk at the joint between the cement board and the shower base, but it set up much faster than I expected and wasn't as smooth as I would have liked. I also filled the cement board joints with "tape" and modified thinset (and covered the screw holes with thinset). Then I covered all seams and joints with KBRS gauging fabric, as per KBRS instructions. Finally, I coated the whole thing (walls and floors) with at least two coats of KBRS "liquid liner" (three coats on the corner & side joints).

As for flexing, I'm concerned that because of temperature and material differences the sides and floor will expand and contract at slightly different rates. If I use something like grout, this might crack. A silicone caulk should absorb those slight changes without cracking... I think.

Thanks!

I would not worry about the expansion between the two materials. I'll assume a couple of things.
The cement board terminates inside of the shower base?
If this is so, you can use a flexible sealant between the bottom edge of the cement and the shower base.
I believe the color matching caulk suggested will do what you need. I you can, stay away from silicone caulk.

 

[TresK3]

Thanks for the replies.

The cement board landed on top of the shower base (there wasn't really a lip on the outside edge, just a flat spot). I used polyurethane caulk (supplied by KBRS) between the backer board and the base. I will definitely go with a caulk between the bottom of the wall tile and floor, and in the corners.

Why do you say not to use silicone? What would you recommend? Polyurethane? That stuff was really difficult to work with.

 

[Wooden Head]

Thanks for the replies.

The cement board landed on top of the shower base (there wasn't really a lip on the outside edge, just a flat spot). I used polyurethane caulk (supplied by KBRS) between the backer board and the base. I will definitely go with a caulk between the bottom of the wall tile and floor, and in the corners.

Why do you say not to use silicone? What would you recommend? Polyurethane? That stuff was really difficult to work with.

Silicone is not a great mastic. It will stick to some surfaces, but how well it adheres can be a problem. Wet silicone will not stick to dried silicone. This is a problem when trying to redo an area. Not very many things will stick to dried silicone.

 

[shoot-straight]

Caulk that matches the grout. Caulk should be used in the corners where walls and floors meet. Caulk will expand and contract with movement,, grout will not.

this- where materials line up in different planes (ie 90 degrees), caulk with matching caulk.

 

[sportbikerider78]

I'm fairly surprised anyone is suggesting use caulk. When you use materials that aren't perfectly straight (like natural look materials) you always end up with some larger gaps where you need to use more filling material. Some of this is even built up to make sure no water settles there.
Some of these are over 1/4" in my case on an outside wall in a very cold climate. Zero cracks with grout.

 

[TresK3]

View attachment 235651 I'm fairly surprised anyone is suggesting use caulk. When you use materials that aren't perfectly straight (like natural look materials) you always end up with some larger gaps where you need to use more filling material. Some of this is even built up to make sure no water settles there.
Some of these are over 1/4" in my case on an outside wall in a very cold climate. Zero cracks with grout.

Nice photo! That's exactly what we're doing, except that the bottom tile is a variety of shades, not just dark grey. My wife and I were debating white or grey grout for the white tile. Really liking the grey look! Thanks for posting it.

I'll put up a picture when I get the tile work finished.

 

[shoot-straight]

google the caulk vs grout debate and read for hours. its a lively one. if its working for you- more power to you. i am re doing my bathroom soon. i will be caulking, they make silicone matched, sanded caulk that looks just like grout. acrylic is crap and useless unless you are painting over it.

i also like your floor. very nice.

 

[sportbikerider78]

Thanks guys. Yup...it is grey grout. We used the same color for tiles and for stones. It made the most sense to us. I love white, but it's just impossible to keep white. I'll accept defeat and start with grey.

We took a TON of time and make sure everything was solid and square. This house doesn't flex much, but it if did, I'd likely lean towards silicone. I have heard people say over and over that the corner grout will crack. Ours doesn't. I have 3 corners with no cracks. Maybe it will...years from now..who knows. It is a 20 min project to scrape some grout out and regrout if it did. Silicone doesn't look good and last forever either.