Grout or Caulk at shower/tub line?

[Jay-T]

I am having new ceramic tile installed on my shower/tub surround. The job is being done well -- with cement backer board etc.

My question is about the 1/8-inch gap between the bottom of the ceramic tile and the existing cast iron tub. Should that space be filled with grout and then use 100% silicone caulk, or should there be no grout there and only use

100% silicone caulk?

[Wayne Whitney]

Since your tub is cast iron, then grout is an option, and I would recommend using grout only. I find that grout is much less likely to mildew there than caulk. It may well crack in a few places over time, in which case you can fill just the cracks with 100% silicone.

Cheers, Wayne

[norminn]

I've lived with all types of tub/wall seals and they were all crap but for silicone caulk. If caulk is applied to an absolutely clean surface, put on smooth, it won't have mildew problems. If there is soap buildup or poor ventilation, it will get mildewy. Scrubbing Bubbles is great for cleaning tile/tubs.

Corners where wall meets wall, floor or tub should be able to FLEX. The thing about filling a tub prior to caulking is, I think, an urban legend.....looks good on paper :o) If the tub moves, there is more of a problem than caulk.

[JimT]

I've never heard of that either. Any movement would be takin care of by the caulk.

To the OP: Caulk around the tub and in the corners of the wall if tiled.

[keith]

Yes, anywhere two planes or dissimilar materials meet. Tile stores (not home centers) have caulk, sanded and un-sanded, that will match the grout closely.