1st contractor is right--grout cracks and water seeps in. Make sure you get a 100% silicone waterproof caulk made for baths & kitchens--often comes with a 5yr mold/mildew guarantee. People often get siliconized caulk mixed up with 100% silicone caulk and end up with mold pretty quick so make sure you get the right one--I'd go to Lowe's or HD & pick it up myself in the desired color and supply it for the contractor to apply just to make sure the right one is used. Better to replace caulk every 5 years than have to rip out, repair water damage and redo.

Hope this helps!

mydreamhome, thank you so much for the information. I'll go to Lowe's or HD and check for the 100% silicone waterproof caulk for baths and kitchens. Would clear one be the safe color to choose?

The 1st contractor also mentioned that there is a grout caulk which has the grout color but it's a caulk. I don't know if that's a good one.

Terriks, thank you very much for the information, which is very helpful. I will make sure the contractor will completely waterproof the tub/shower surrounding before any tile is applied to the wall. I have a question. If the surrounding is waterproofed, what's the purpose of caulking? Do the two corner vertical lines between wall tiles also need to be caulked besides the interface lines between tub and tiles?

Thank you very much.

You caulk at the change of planes, because the grout can crack, and then it doesn't look good. Caulk is much more flexible.

Yes, they make a sanded caulk. I personally do not recommend it. The sanded caulk hardens and still cracks & allows water through like grout can do because it's not flexible like silicone. Stick with with the 100% silicone and you'll be happy.

terriks and mydreamhome, thank you so much for your information, which is very helpful.

I've used sanded caulk and it hasn't hardened and cracked even though it's been in place for years. I like that it's color matched to my grout and looks nearly identical to the grout.

I do however agree with the consensus that there should be waterproofing to prevent mold and mildew (not just tile with grout and caulk) and that the caulk at the change of plane is necessary to prevent unattractive grout cracking.

The vertical wall seams crack more readily because the house shifts and moves. Ive tried grouting only and going back to caulk with sanded grout caulk or silicon only after a crack develops, hoping in some cases it will not. Sometimes it does not crack. Some contractors caulk all seams as a matter of course, no callbacks, safer.
I liked the idea of sanded grout caulk to match your grout color It has not held up for me in wet conditions, such as the top of the bathtub where the wall tile starts, etc. , definitely not along the shower floor where the wall tile starts. It has held up in other areas though, and looks nicer when it all ties in. I agree, mildew on silicon is unsightly. Every bathroom has different conditions, including ventilation, moisture, etc. Some people have to clean out and recaulk the silicon every year or two. Whether its allegedly mildewproof silicon or not.

One night, as my family was sitting at the kitchen table, water started to drip from the fixture over the kitchen table.

The next day, my dad ripped out the ceilng, only to find that it was full of water (though no water stains had yet appeared). We lived with a fully exposed ceiling for 6 months because not one of the plumbers who came in was able to figure out why water was leaking from the bathroom upstairs into the kitchen.

It turned out that a microscopic pinhole next to the tub was the culprit. It hadn't been sealed correctly and caused about $1k worth of damage as a result.

I used a clear silicon caulk on all exposed edges of my tub (tub/wall, tub/floor, shower door/tub) when I moved into my house, just in case.

Thank you so much for all the responses, very helpful.

terriks, you said "the tub/shower surround should be completely waterproofed before any tile is applied to the wall. "
Would it be better that I buy schluter materials for the contractor to waterproof the surrounding behind the tiles?

Really appreciate your help.

Here is a link that might be useful: Schluter systems

A surface applied membrane is IMO the best way to go. That way there is no where for moisture to be absorbed behind the tiles. The shower will dry out much faster, decreasing the chances of mold and mildew forming.
When I built my own shower I used the Schluter Kerdi kit. Just make sure that your contractor knows how to use Kerdi. An unmodified thinset needs to be used per Schluter instructions. Another option is a paint on waterproof membrane such as Redguard or Laticrete Hydroban.

I'm sorry, but mydreamhome is wrong. First off, even if grout does NOT crack, water will get through. Grout is NOT waterproof, and caulking isn't meant to waterproof those joints. It's meant to be a flexable joint where tile meets a different surface, or a different plane, to allow for some movement without cracking. Secondly, the ONLY difference between sanded and unsanded acrylic caulking is the sand. Sanded caulking will NOT get hard. It WILL stay pliable, and in fact, I use one or the other or both on every installation I do, and NEVER have a problem with either one.

My handyman installed a tub but used Permacolor grout in between tiles and bathtub. Should I use a silicone caulk over the grout or ?

My handyman did not caulk under the baseboards in the bathroom. What kind of caulk should I use?

" My handyman installed a tub but used Permacolor grout in between tiles and bathtub. Should I use a silicone caulk over the grout or ? "

Grout needs to be removed (as much as humanly possible) and the joint filled with color matching 100% silicone caulk.

" My handyman did not caulk under the baseboards in the bathroom "

If you feel it has to be caulked (not always done), usee a similar 100% silicone caulk.