I found this modular (3-piece) 3-sided plastic tub/shower surround installed at a recent renovation. I can't find any identifying information on it, nor can I locate the contractor who installed it.

There are deep 1/8" gaps between the three pieces of the surround, as well as between the surround and the tub. Should I be filling these gaps with silicone caulk?

Here is the (horizontal) gap between the surround and the tub:

Gap between surround and tub

And here is one of the vertical gaps between two of the pieces of the surround:

Gap between two pieces of the surround

  • How do you clean this type of shower? This is what I have and gross stuff falls out from between that horizontal gap.
    – Hildkd
    Commented Mar 17, 2023 at 3:14

3 Answers 3


You probably don't need to, as the lap in the surround design will drain water effectively. However, those are traps for mildew and grime.

I'd clean them as deeply as you reasonably can with rubbing alcohol, then put in a bead of 100% white silicone. If you trim your tip carefully you can inject caulk to a depth of about 1/2" for good grab.

The tube tip will tool the caulk to some extent if you size and shape it correctly. Use caulk flow rate and movement speed to prevent squeeze-out of caulk around the tip. You should then be able to use a damp finger to apply a final cove surface without squeezing caulk out onto the shoulders of the panels. Use firm pressure and wipe your finger immediately if caulk starts to pile up under it. The result will be a nicely coved joint that's nearly identical to the factory inside corner joints.


NO never caulk in seams. They are built like this to “breathe and vent wall. Panels being super cold and hot can build condensation and moisture. This is a means for the moisture to escape. Sealing this WILL cause mold and mildew

  • 1
    This makes little sense as there are single piece shower units with no joints at all.
    – Olivier
    Commented Aug 19, 2021 at 1:07
  • @olivier on showers with no joints at all yiu would need to carefully caulk each one
    – Kris
    Commented Aug 19, 2021 at 1:39
  • 1
    "each one" what, @Kris? Each of the non-existent joints?
    – FreeMan
    Commented Aug 19, 2021 at 16:35
  • @freeman. Yes indeed the nonexistent ones are most likely to be missed during the unnecessary caulking process. Thus leads to imaginary leaks that are difficult to see.
    – Kris
    Commented Aug 19, 2021 at 18:36
  • @Kris what I meant is that the "it needs to breathe" argument is BS because there are showers without any joints at all for that breathing. The joints might be designed to not require caulk but the argument here is still plain wrong.
    – Olivier
    Commented Aug 20, 2021 at 15:24

You never caulk them - never. They can’t leak as per the design. They float and expand and contact, as they are thin.

You mentioned a one piece, and they are a molded fiberglass rigid design they don’t expand or contract.

If you caulk the sectional walls you will ruin them.

I have been installing them for many years.

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service and acknowledge you have read our privacy policy.

Not the answer you're looking for? Browse other questions tagged or ask your own question.