Bathtub was re-caulked by maintenance few months ago. 2-3 months after the caulk that the guy put in fell out. Given few other things that maintenance did that were poor jobs I am not sure I trust them anymore for anything I can do myself.

My bathtub has very varying space between the edge of the tub and where the tile starts. It varies anywhere from 0.5" to 1.25". It looks like there are multiple layers since in one part it fell out, and I am not sure what is in there (grout?). How should I go about repairing it?

My initial guess is:

  • Let the bathroom dry overnight first
  • borrowing multimax tool to clean out the whole area between tiles and bathtub (1*)
  • utility knife to for basically same purpose. Also will use this to clean out the group between the tiles that are molded (pretty much entire thing)
  • silicone caulk (not 'water clean up' type) around bathtub (2*)
  • grout for between tiles

1* - How deep should i go with the multimax oscillating tool?
2* - Is it too wide to just caulk it? Should I use grout? Combination maybe? Anything else to add?
mosaic tile

Any steps I missing that I should do? to the right of the faucet under the faucet under the soap holder

Approximation of the bathroom

  • What is the problem you are trying to solve?
    – DMoore
    Commented Mar 1, 2016 at 20:12
  • It looks like the tile is mounted on standard Sheetrock. Once that stuff is wet it really falls apart and nothing will stick to it. Make sure to document this problem so you are not held responsible. Putting in new grout will never match in color and cutting a mess like this you might find tiles falling off right and left. At most I would bridge the gap making sure to touch the tub and tile so the calk has something to stick to.
    – Ed Beal
    Commented Mar 1, 2016 at 20:13
  • @DMoore I want to get rid of the mold
    – StanM
    Commented Mar 1, 2016 at 22:12
  • 1
    I'd consider installing trim pieces in front of that gap, caulked top and bottom, to achieve a consistant and minimal gap. These could be cut/ scribed to fit to obtain a nice straight line parallel with the existing grout lines.
    – keshlam
    Commented Mar 1, 2016 at 22:29
  • 1
    @Iggy - there is absolutely nothing wrong with a large grout gap by the tub. That is 1% of the issue. The water isn't hitting that grout and climbing up the wall.
    – DMoore
    Commented Mar 2, 2016 at 5:50

4 Answers 4


Just my thoughts on this:

  • I see mold everywhere, even by the faucet

  • the first thing you need to do is figure out what is behind the tile. If it is drywall you are absolutely wasting your money doing anything.

  • if it is not drywall the first thing I would do is give it a heavy heavy spray of anti-mold cleaner. Maybe 2-3 doses. Scrub away mold using as little water as you can (this is a whole different question and will take a lot of man power). I would then either not use the tub for a couple weeks or put up plastic sheets around tub. You can get some painters plastic and tape it 5 feet high and your walls will stay dry.

  • if after a couple of weeks (at minimum) you still don't see the mold come back then we can talk about grout and caulk. If the mold grows back either take down tile or keep plastic sheets up. Either your mold is out of control or you have a leak behind wall.

  • if no mold you can grout and caulk. Let's start with the gap by the tub. This is too big to caulk for sure. There is nothing wrong with grout here. Do not install trim or other tiles at the bottom, that introduces more problems. What happens if water gets in this first grout line? It sits on tub, no big deal. Your mold is coming from above. After the mold is gone simply add more grout over this.

  • for the rest you are are going to have to scrape out caulk and grout, regrout, then caulk and quite possibly put some sort of waterproofing on the whole area. The water could also be entering through the tiles themselves. If they are old ceramic these will let water through.

  • my final thought is just I would never worry about doing anything more than hitting it with some mold spray. All the other time/money is a waste. You can buy cheap tile for $100 and another $50 for grout/thinset. Add another $50 for backer and you are at $200. Thinking about the time and money you are going to spend I would just wait and do it right.

  • Thank you for an awesome answer. So for my next steps - I found some information about mold blackmold.awardspace.com/kill-remove-mold.html - based on this I am planning to 1) Do Borax + Vinigar mixture, 2) soak paper towel in bleach and stick into that crack for a bit, 3) do Baking Soda one. After that I will wait a few weeks to see if it starts growing back, and if it does I will repeat the process maybe with bleach or something like that. At that point I will put a layer of grout (?) and then caulk between the grout line and the bottom tile - is that right?
    – StanM
    Commented Mar 2, 2016 at 15:14
  • Also is there a guide how to properly do grout & caulk? and would that be better than small tile + caulk?
    – StanM
    Commented Mar 2, 2016 at 19:39
  • The cleaners are just part of the process. The area needs to be properly scraped. I use a cleaner from Big Blue box that is in a pretty plain dark blue container (if anyone knows the name). The key is to let it dry out for a while and see if it is still growing from behind. Also it sounds like your bathroom has some humidity and airflow issues - this needs to be solved. On the grout and caulk that will take too much room to respond and that is its own question.
    – DMoore
    Commented Mar 3, 2016 at 15:12

Listen to @dmoore, but here's an alternative take.

You're not supposed to caulk gaps larger than a 1/4", but what choice do you have here? This tile is a mess and should be torn out and re-done. I'm guessing that's not something you want to get into or pay for.

The recent caulk that just fell out was probably due to poor prep. They probably didn't even clean the surface first. Clean out all the old caulk. Clean off the mildew and soap scum. Let it dry over night then lay down some painter's tape at least 1/8" away from both sides of the gap. Slather on some 100% silicone caulk then use the back of a plastic spoon to smooth it down. Peel away the tape to leave nice a clean edge.

It's not really the right way, but it'll last for a few years and won't cost much.

  • Based on @dmoore's answer that's what I will basically do. Initially I will try my best to kill the mold thats there but the end result I will do what I can to just keep it away.
    – StanM
    Commented Mar 2, 2016 at 15:10

Responding to your Question & Comments. You're absolutely right. Get the old caulk out however & with whatever works...Multi-max, screwdriver, utility knife, etc. Fill the entire void & more (up behind the tile) with caulk & bridge that gap to drastically reduce the area that future mold can take up residence. This will also make cleaning a lot less involved. Only the surface matters concerning mold.

After this, there's no need to rip out the caulk in the future. You just scrub it clean & apply just enough new caulk to pretty it up for one, but more importantly to fill any gaps that may have appeared.

However, the main & even sole reason for mold is nothing but ventilation. Mold doesn't like wet & mold doesn't like dry, mold likes right in the middle. If the area can't dry quickly after it's been wet then you'll get mold. So, you must use your window or exhaust fan liberally. Open the window (top sash) or run the fan (either, not both) for 30-minutes after showering & don't stop either until you can actually feel that the sauna is mostly gone.

  • I think my only option is to try to get a dehumidifier. It's an old apartment so no exhaust fans, and the window points into a corner with 3 sides, so not much ventilation.
    – StanM
    Commented Mar 2, 2016 at 15:11
  • Aaaaaah, there's the problem. Dehumidifier's don't work too quick from what I've seen, but better than nothing. However, just a hole through the wall is all a fan needs. And, a window's a window & you could put a fan there. If it's a double hung windows you can put it up on top so you don't even notice it. Make the filler out of rigid insulation, put a dryer vent outside & a small fan inside, centered or to 1-side & foam rubber the sash gap...like a window AC unit setup, slightly reversed. Wiremold Cable Raceway for easy electrical tie-in to the light's operation.
    – Iggy
    Commented Mar 2, 2016 at 15:24
  • I just added a picture of the mosaic tile that I got as well as a layout of the bathroom. The window is pretty small, I would have to measure how much the width is but I think it may be below 20". Aside from that I would need to make the wire go along the ceiling into the only available outlet. The other option I am thinking is just simply having a fan available that's strong and just turn it to max.
    – StanM
    Commented Mar 2, 2016 at 19:32
  • Yeah, if you're touchy about the maintenance guys wiring it right. Then, still just a little fan is good or whatever you already have to put on the floor & shoot out into the rest of your place. Leave the window out of the equation. If you have a kitchen exhaust that actually goes outside then you can use that to remove excess humidity if needed, but the rest of the place should suck it all up with no problem at all.
    – Iggy
    Commented Mar 3, 2016 at 0:19

This isn't really an answer to your question -- that's been done well by others.

My concern is about how the tub got that way in the first place. Either it was a terrible tile job initially (possible, especially if the tub was set out of level, which is terrible all by itself), or there's moisture/rot in the subfloor that's caused the tub to sink. Can you get any access underneath to see how it looks? Does the floor feel bouncy at the edge of the tub? Do you have cracked tiles in proximity?

If it does turn out that you've got rot/moisture issues, you're looking at a pretty complete bathroom gut, so it takes the pressure off fixing any of this minor grout/caulk stuff and starts you budgeting for the big fix.

  • there's no access to below the tub, it's a solid piece down to the floor. It doesn't feel bouncy at all, feels very solid actually. There have been some leaks few years ago, so it might be that there's an issue in the subfloor.
    – StanM
    Commented Mar 2, 2016 at 19:33

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