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How should I seal tub/tile gap?

Hello. I'm trying to fix worn out grout above my bathroom (white porcelain) tub. I dug out much of the old grout, and 1/2 of the botom tiles came out in the process. This row of tiles is cut to only about 3/4" high, and 4" wide. The spacing between tiles is 1/16", and 1/4"-1/2" between the tiles and the tub. Behind some tiles is a bit of the backing wood wall, and only empty space behind others because the backing board ends short. In some places I could glue in thin 3/16" strips of wood onto the riser beams behind. I repositioned the tiles by gobbing in 'SimpleFix Pre-mixed Adhesive & Grout, for grout joints 1/16" to 3/8" ' behind the tiles on the tub, the bit of backing available, and between the new tile and it's neighbors, but not filling in all the way so I can now do a surface grout after it set (I thought it might shrink and not work if I filled in, adhered the tiles, and grouted all the way in one step.)
Now I need to grout or caulk the positioned tiles and am not sure what to do. I read that regular grout will crack on the tub/tile gap because of motion when the weight of water/bather enter the tub.
My questions are:
1. What is appropriate to use in this tub/tile gap? I read that normal grout wasn't flexible enough or doesn't bond the tub well enough to use at the tub/tile joint. The "adhesive grout" has an "acrylic copolymer"; will it be good for this purpose? If I should use caulk, as I'm starting to think, what kind? The manufacturer of the silicone grout I have says it's not good for gaps deeper than 1/4".
2. The "Adhesive & Grout" stuff is sandy, will I damage the porcelain (I think) tub, or the ceramic (I think) tiles? It does seem OK so far. It seems sandy. I read contradictory things on whether sanded grout is OK for 1/16" gaps, and this adhesive/grout feels sandy.
3. How about the joint where 2 walls come together? The existing had silicone behind caulk. What should I use?
Thank you. Any help is apprecitated.

Re: How should I seal tub/tile gap?

The area where the tiles meet the tub should be caulked for the reason you mentioned. The tub will flex when weight is applied inside the tub .... grout is not flexible and will crack.

As for the corners I personally always use caulk as well.

Make sure to use a good quality caulk formulated to resist mold and mildew ..... the tube will usually indicate for use in tub and shower locations.

Re: How should I seal tub/tile gap?

Thanks for the reply. OK, I'll caulk. I have some GE-II 100% silicone white caulk, I'll use that (unless someone thinks otherwise).
There is a large gap between the tile and the tub that I'll caulk with the silicone. There's a small 1/16" gap between the new bottom tiles and the tile above them. I guess I should use the grout adhesive there to hopefully 'glue' the tiles to the ones above, and to match the grout as is between all other tiles. However, I'm a bit concerned that the bottom tiles were 'glued' onto the white tub by all the adhesive/grout I gooped onto the tub (behind the tile) to position the new tile in place. In some cases there was no other backing behind the tile to position it in place. If the tile sticks to the tub, the weight of water/people could crack grout above the tile. Hopefully if I fill this crack with grout, and grout inherently (I think) not sticking as well to tub/porcelin the tile will stick to the one above, and any crack in the grout will be below the tile where it will now be covered by silicone caulk. I'm not quite sure if I should use silicone caulk above these tiles also.

A. Spruce
Re: How should I seal tub/tile gap?

I would not recommend the use of silicone! It's extremely messy, even if you know how to apply it, and when it fails you'll have a bugger of a time getting the old off well enough to get the new to stick to it. Once you've used silicone you've pretty much ended your ability to apply any other caulk, including silicone, without boatloads of cleaning and prep.

Notice I used the term "when it fails". Silicone isn't going to last any longer than latex caulk, is infinitely harder to apply, and infinitely harder to deal with when it goes bad. Go with a good tub and tile latex, and get one that is non-adhesive because it stays a little more pliable than the adhesive formulations.

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