New tile falls off shower walls

16 years ago

I'm installing tile in a shower over Durock cement board. I went to Menards to get all the supplies, told the clerk what I was doing and he sold me Mapei Ultralite Mortar to hang the tiles. It says that the mortar is for wall and floor tiles. I'm using a 1/4" trowel and I wait 5 minutes after mixing before applying the mortar. It feels like I'm doing everything right, but some of the tiles I can easily pull off the next day and others just fall off if I look at them wrong, so something isn't right. I suspect that maybe I should have used mastic instead or perhaps there is something wrong with my technique. I suppose grouting the tiles will help them stay, but it seems to me that the tiles should be stuck solid before grouting. Some of the tiles are stuck very well and some just fall off....I really can't figure out my problem. Also, as to technique, when applying the tiles into the bed of mortar, are you supposed to push them down really well, or just sort of set them into the mortar lightly and leave them be? Another thing that disturbs me is that when the tiles fall off, you can see on the back of the tile that no mortar is on there...this makes me think that the mortar is not bonding with the tile at all. Thanks for any advice you can give!

Featured Answer

brickeyee

16 years ago

When starting the job (and with a new batch of mud if you do not measure everything or have a good feel for the mud) you need to set and then check a tile.

You take a single tile and go all the way with it in a small area.

Apply mud, comb it out, set the tile, beat it in, then pull the tile up.

Check for coverage onthe back of the tile.

The mud needs to be wet enough to flow out from the combing ridges and cover the entire back of the tile.

After you have verified your mud and technique, scrape the area clean, throw the mud away that you removed, and proceed with the rest of the work.

If it takes more than 4-5 minutes to place the tile and beat them in an area you made to large an area.

As you practice you will be able to set and beat in the tiles faster, so you can cover a larger area with mud.

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Comments (6)

macv
16 years ago
Unless you are fast don't spread too much mortar at a time.

Mapei instructions:
Place the tiles firmly into the wet mortar. Push the tiles
back and forth in a direction perpendicular to trowel
lines, to collapse the mortar ridges and achieve
maximum coverage. Ensure proper contact between
mortar, tile and substrate by periodically lifting
a few tiles to check for acceptable coverage.
Remove excess mortar from the joint areas so that at
least 2/3 of the tile depth is available for grouting.
homebound
16 years ago
Could be the mortar is a bit too dry. They say it should be mixed to the consistency of peanut butter, but I would amend that to "creamy peanut butter", if you know what I mean. Also, after waiting 5, mix again, and also remix the bucket periodically (a couple quick turns of the mix) with your margin trowel (rectangular hand twowel).
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homebound
16 years ago
And, as mentioned, you have to "set" the tiles into the mortar. I whap them "more than gently" with a rubber grout float, but a little bit of the push and wiggle can do it also.

Full disclosure: I'm not a tile pro, but have done more than a handful of these jobs. One has to do to that to gain the hands-on experience. Final caveat: don't follow the methods on the diy tv shows, especially the one that rhymes with "cr@p-tastic". They are mainly good for design ideas and that's about it.

Good luck with the project.

BTW, don't make the mistake of adding "a little bit of water" to a mix that's drying out too quickly. That means you mixed too dry to begin with - dump it and make a fresh batch.
MongoCT
16 years ago
Realize that when you use a 1/4" notched trowel, after the tile is set and in embedded in the thinset, the 1/4" square ridges of thinset should be compressed to a nice even 1/8" thick layer of thinset that fully adheres the tile to the backer board.

Question...or maybe a comment...after you let the thinset slake for the 5 minutes, make sure you mix it up again prior to spreading.

Make sure the backer board is clean. No dust.

You can try using a semi-wet sponge to wipe the cement board down prior to thinsetting. Wetting the cement board will prevent the porous and dry cement board from sucking the moisture out of the thinset prior to the thinset having enough time for a nice cure.

Try burning the thinset in first. This means using the flat side of the trowel to apply a skim coat on the backer board, you're trying to force the thinset into the pores of the backer board. "Apply a skim coat" really isn't correct, as you're really just filling any micro-voids in the surface of the panel. You're not trying to leave a measureable thickness. After burning in, flip the trowel and use the notched side to apply a measured amount.

Try burning thinset into the back of the tile too. Again, you're not looking to apply a thickness, think of it more like "wetting" the tile with thinset.

When you set the tile, press it in to collapse the ridges. Slide a trowel under the edge and pry the tile off. You should have near full coverage on the back of the tile, and there should be no umcompressed ridges of thinset on the backer board.

What size tiles are you setting? Ceramic? Stone? What size?

What kind of "cement board"?
paintguy22
Original Author
16 years ago
It's Durock cement board. The tiles are 4.25" standard square ceramic tiles...seem to be the cheapest of the Majestic line. The bond with the Durock is fine. When the tiles do fall off there is no mortar on the tile, but the mortar on the cement board is really stuck on there. It sounds like I'm just having some technique issues which basically means that tiling is a PITA! I was hoping that I was just using the wrong adhesive.