regrouting a "shifty" shower unit

[mmatthews]

My husband and I live in an old home. Floors are not level, etc. We finished tiling the shower stall (corner unit-swanstone base) and the corner grout line and grout around soap dish (which is also corner mount) continues to crack, break apart and fall out of the joints. I think the floor shifts when my husband gets in and out of the shower. He is a pretty big guy. Can't remember what grout we used (except) is was unsanded. Think the grout lines are around 1/8", with the grout around the soap dish a bit wider. Should we try to regrout, or use some type of flexible caulk? The tiles are white as is the grout. Does caulk yellow with time and cleaning? Is there a recommended brand for this use? Please help, as we use the shower quite often (family of five) and don't want to ruin the shower. Also, how long do I wait for the walls to "dry out" before attempting to fix? I'm sure some water has gotten behind some of the tiles.

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[Davestone]

If you used mastic, and or greenboard or plain drywall, i'm afraid the shower is doomed.

[mmatthews]

What do you mean doomed. Isn't there a way to take the old grout out and reseal with caulk? We just had this bathroom put in only a year ago. My husband said he thinks the contracter used mastic and some kind of "wonderboard" behind the tiles in the shower. Does this make any difference!? God I hope so, we can't afford to redo!
Moe

[Davestone]

If it's a cbu, a cement board or Hardi, the board won't disintegrate, but a drywall product will hold moisture and fall apart.No sealer or grouting will stop it.These problems usually surface at the 1 to 2 year range.Mastic holds moisture, and transfers it to the board beneath, there should also be a vapor barrier under the board,look through our Liberry for a proper shower build.

[mmatthews]

...We'll have to do something with it and pray it holds up. We can't just leave it the way it is...
Do you recommend any kind of caulk? I know no grout with withstand any movement. This old house just hasn't quit giving us a surprise or two.
Thanks for any more advice you can give.
Have a great day!

[Davestone]

Silicone, i guess.

[tsbrewers]

If you know what kind and what color of grout was used, you can usually get color matched caulk. Just keep in mind it won't match. :) But it will move and give a little where as the grout won't. I would dig out as much grout as you can, then personally I would put a fan by the shower and try to give it a day or so to dry out, then caulk, then wait as long as you can to use it again.

I am no pro, so hopefully one of them will back this up or help more.

Brew

[mmatthews]

Thanks everyone.
I'm going to try and use a silicone caulk and pray for the best.
I know we used some special kind of board behind the tile specifically for bathroom/shower/tub, not just basic wallboard. As for any other barrier, I'm not sure.

Any other advice would be helpful.