Background: I have just finished tiling my shower/tub. Everything has been waterproofed with mapei liquid membrane and fiberglass tape on the seams over cement backer board. The backerboard was installed by a contractor and the holes are a bit bigger than the mixing valve and shower pipe need (but not much). We were using glass tile, so I couldn't use a nice hole cutter to get the CLOSEST possible fit to the edges of these holes or the edges of the fixtures, but all the cuts will be completely hidden by the estucheons/flanges. I used a pipe collar on the copper pipe for the slip on tub spout, but that wouldn't have worked for the shower pipe (needed to be a threaded brass pipe) or the mixing valve (the valve was larger than the only size they seem to make the collars in.

My question is: Do I need to do anything to fill in those smaller gaps between the shower fixtures and the edge of the tile? Do I grout right up to the edge? Do I pre-fill with silicone or kerdifix? Do I just install the flange and estucheon over top?

Thanks in advance.


Mixing Valve

  • Your pictures did not come through. Can you edit your question and re-attach the photos please. Click the mountain/ sun icon to add an image.
    – Kyle
    Commented Aug 27, 2022 at 17:16
  • 1
    Till the pictures show, usually want any holes in the wall sealed. Silicone does a good job. Would seal the flange and escutcheon to the wall with silicone also, maybe leaving a bit open on the bottom.
    – crip659
    Commented Aug 27, 2022 at 18:13
  • Pictures attached. Yes, I was thinking silicone to fill the gaps, but the gaps left by the contractor were large and I need to be able to fit the shower pipe after the fact, so I wasn't sure how to work around that. Commented Aug 29, 2022 at 23:20

1 Answer 1


No, you don't need to fill in the spaces between the tile and shower fixtures. Since you've stated that the escutcheons / flanges will completely cover the gaps, all you have to do is caulk the escutcheons and flanges all the way around after installing them. You'll also want to caulk around the spout where it meets up against the tile.

  • Thanks so much, that is what I planned. I fixed the pictures, can you check to make sure this matches your initial ideas? Commented Aug 29, 2022 at 23:19
  • @user2934942 The only thing you have to worry about is that the escutcheons for both the valve and shower arm cover the gap completely so you can caulk around them. If you can, here's not reason to fill the gaps since the tiles are well supported by the wall. If you will feel better about filling them in with grout or silicone after installing the shower arm, then no problem. Make sure the shower arm in tight after you install it. You sure don't want it leaking back behind the wall.
    – JACK
    Commented Aug 29, 2022 at 23:50
  • One thing to check: is the whole assembly able to move slightly? If so, opening/closing the valves might cause enough movement over time to make the caulk separate from the tiles and introduce a leak. This would then allow water to seep into the structure.
    – MiG
    Commented Aug 30, 2022 at 19:22

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