It looks like he is suggesting an open crevice between the bottom edge of the tile and the rim of the tub and I 've never seen that suggestion before. I would think mold would form easily in the space in front of the tub flange.

No he's not suggesting an open crevice. He is saying that the space between the tub deck and the tile should be grout, not caulk. It's to allow any moisture down there to wick out. This actually makes sense to me, but I have always caulked and after a while it always gets kind of moldy from trapping water behind it.

I agree, the caulk there always gets gross. I'm about to grout our new tile surround around our new tub. I wasn't going to grout there along the bottom because I thought caulk went there to keep the water out.

If I put grout instead, what is the worst that might happen?

The grout cracks because the tub expands and contracts slightly and moves up and down slightly when it is empty vs. full., essentially it's a change of plane, and of substrate.

Schluter makes a profile for this area but I don't know how successful it is. It doesn't appear to have weep holes.

I just looked at mine and I couldn't believe my eyes: they used grout! I am sure the grout is from 1985 when the house was built and the grout is still fairly intact. I was quite surprised that it looked so good!

You cannot always tell from just looking. A pokey tool will tell you for sure. Grout is like cement. HARD. But sanded caulk looks just the same as sanded grout, except that it gives. Changes in plane or differing materials expand and contract differently. It took about 3 years for that to show up in part of my kitchen countertop/backsplash.

Grout is porous. (well except for the epoxy grouts) Even with most sealers. When your silicone caulk is getting icky it is because water is getting behind it, probably thru the nearby grout.

I hope a caulk expert will set me straight if I am off base here.

-Babka

I have the same concern. I read on many posts that water needs to run down the vapor barrier behind the cement board. But I cannot figure out how to get that water out. If you caulk it will trap the water. I am thinking no caulk or grout instead. The crack that will appear in the grout may act as a way for the water to exit. I was considering redoing the cement board and using a membrane. The water behind the wall concerns me.

I still would like to know how water is going to get "behind the cement Board" mayflower?

I thought water didn't normally go behind cement board...I hope it doesn't, anyway. We have cement board against the studs, then it's protected with RedGuard, then tile/grout.

If any water gets back there, it would just be a bit of moisture that could then evaporate. If a LOT gets back there, such that you need it to drain out, doesn't that mean a major hole or leak is present? In theory, you wouldn't continue to use the tub/shower if that much water is entering the wall...I wouldn't, anyway.

I have the same concern. I read on many posts that water needs to run down the vapor barrier behind the cement board. But I cannot figure out how to get that water out. If you caulk it will trap the water. I am thinking no caulk or grout instead. The crack that will appear in the grout may act as a way for the water to exit. I was considering redoing the cement board and using a membrane. The water behind the wall concerns me.

I have the same concern. I read on many posts that water needs to run down the vapor barrier behind the cement board. But I cannot figure out how to get that water out. If you caulk it will trap the water. I am thinking no caulk or grout instead. The crack that will appear in the grout may act as a way for the water to exit. I was considering redoing the cement board and using a membrane. The water behind the wall concerns me.

Water buildup behind the tile on a properly built unit is marginal. What you get is water vapor for the most part, which generally gravitates to the morter and evaporates on a surface applied build, or on the cement board in a traditional, plastic-over-the-studs application.

100% Silicone should be used at any change-of-plane because of the small, perhaps even microscopic movement that is inevitable there. With a solid, cast tub and mud walls, you could probably "get by" with grouting those joints.

With the usual, flimsier tubs, I like to fill with water, thereby "loading" the tub and then caulking in that position so that stress is minimal on the caulk under use and heavy weight.

My contractor for my bathroom and kitchen remodel is fantastic.However he tells me that there does not need to be a sealant around the tile and inside walls of the tub? I have a steel /porclien tub with red sealed back board..is this true?