How do I caulk this beast? I was trying to replace the caulking, took out the old caulking to find out that the bathtub was improperly installed, and the tiles are not over the lip. There is this half inch gaping hole such that the caulking needs to do all the work to keep the water out. I know the ideal thing to do is to redo the bathtub installation, but I need to have this fixed right now and may be able to take the larger job later.

What is the best way to go about this?

Tile on top part of image, bathtub on bottom part of image

Here is a further away view:

enter image description here

Any help would be appreciated!


  • Do you have a picture from a perspective further away?
    – Edwin
    Jul 23, 2014 at 0:11
  • Hi @Edwin - yup I just uploaded another photo. Thanks for your comment!
    – Alfredo
    Jul 23, 2014 at 1:52
  • 1
    Is your water really that blue? If so I'd suspect you have acidic water corroding copper pipes. That could be bad for you (if you drink too much of it) and your pipes... They'll start to develop pinhole leaks.
    – aaron
    Jul 23, 2014 at 6:18
  • Well I'm hoping it's just the photo but I'll have to look into it thanks for pointing out.
    – Alfredo
    Jul 23, 2014 at 12:14

2 Answers 2


It looks like this is a tub that is not meant for installation up against a wall. Though it's hard to tell from the photo. Looks like a drop-in tub. Tubs that are meant for installation along a wall have a flange (not a lip) that the backer board goes over. This is what actually keeps the water in the tub. If this is purely a drop-in, you'll want to replace the tub at some point, because you will have leaks no matter how well you caulk (I'm assuming you're using the tub as a shower too). There are some manufacturers that make non-integral flanges for their drop-ins, but they aren't ideal.

To caulk the gap, find some caulk backer that will fit into the space. They are made of foam and come in a variety of sizes. Put the backer in neatly, and then caulk over the backer. Use silicone caulk, making sure everything's bone dry before application. I like to use a caulk tool to make things neat. I see you have masking tape up, which is a good thing. Carefully remove the tape right after you caulk, before it sets.


I agree that you have the wrong tub as Edwin points out and a half inch is way too big of a gap to caulk. I run across these issues a lot on flips. Putting in a tub is a pretty expensive job and could kill the tile job - that looks pretty good except for your issue.

I would suggest a trim piece. They make plastic trim pieces that will handle this and you would simply glue them (silicone) and silicone the top and bottom. To make things even nice I have used a contrasting piece of marble or granite for the trim too. You have the brown tile on the right. I would simply call granite place locally and say I need a piece that is 2-3 inches times 5 feet. They will have something brown and a scrap. Probably $30-40 if they polish it. If you go stone though your tile job has to be pretty straight.

  • I agree -- quarter-round trim, mitered at the corners and caulked into place, would be one classic solution. This is available in tile as well as in stone; I have no idea what the cost difference would be.
    – keshlam
    Jul 24, 2014 at 4:27
  • @keshlam - I didn't mention the quarter round specifically because I am thinking the gap is a little over half inch and it might not work - but that is what I would use for 90% of my big gaps on tubs. I for one would something substantial if there was a gap that big.
    – DMoore
    Jul 24, 2014 at 5:25
  • Valid point. The concept's the same, anyway: Don't try to fill it with caulk, put something solid there -- and if you're going to do so, you might as well make it decorative. "I meant to do that!"
    – keshlam
    Jul 24, 2014 at 19:35

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