Background: I've moved into a house 3 months ago that I have been renovating for a while. I have done a lot of the work myself but I left my builder to do the plumbing and tiling while I was away for work.

If I spray the tiles in the shower for 5 mintues, water starts tricking out from behind the shower tray.

If I just run the shower into multiple buckets then no leak occurs so it can't be the pipes or the waste. I have uploaded pictures here (You can see the shower tray is not flush with the wall) I re-siliconed around the tray / tile boundary and I tried a grout sealer which seemed to stop the problem for a few weeks but now the issue is back again.

I know he tiled straight onto green plasterboard and used Bal Micromax 2 grout.

  1. Do you think the grout has failed? Would this happen if we did not let the grout cure for long enough? How long is not long enough?
  2. Should I expect the grout to be waterproof? If not is their waterproof gout on the market?
  3. Would removing the grout and re-grouting fix the problem?

I also thought about removing the bottom row of tiles and trying to reseat the try against the wall but I am not sure that will help either...

He was a nice guy so I am sure this is how he always does it and I know he has done 50+ jobs without issue (unfortunately he has moved country so I have lost contact with him and cant even bounce some ideas off him to troubleshoot)

  • 3
    Looks like a poor job. Tray should be flush to the wall, tiles should be installed over the lip of the tray. Tile should be installed over cememtboard not greenboard in a tub or shower surround. Feb 3, 2015 at 4:41
  • Organic, do you mean the tile fronts need to be over the tray or the tile backs need to be over the tray? If both then why?
    – Joe
    Feb 4, 2015 at 8:00
  • There should be some sort of lip running around the tray where the tray meets the cement board on the wall. That lip should be up against the cement board and then the tile should come down over the top of it. Hard to tell if it was done that way or not from the photos but from what I see and the fact that it's leaking it doesn't look like a good job. Feb 4, 2015 at 16:34
  • What is behind the tiles? That doesn't look like backer board.
    – DMoore
    Feb 23, 2015 at 3:24
  • Shoot your tiler. Using greenboard in a shower is an absolute no-no unless you're putting an expensive waterproofing solution like Kerdi over it.
    – Paul Price
    Apr 21, 2018 at 0:21

3 Answers 3


Tile over green drywall is not waterproof; you will get water migrating through the group and into the drywall. The best thing to do is to tear down tiled walls, put up a new solid backing, and then put a waterproof membrane over the backing. Then tile goes on the backing.

Kerdi is a common backing, and that will be waterproof on top of a drywall backing, though I'd probably use a fiberglass-reinforced version.

  • Absolutely right about the greenboard. An alternative to the proposed solution is Hardiboard down to the shower tray, overlapping the lip, then a couple of coats of Redgard. Pay a visit to the Floor Elf (floorelf.com), tiled shower guru.
    – Paul Price
    Apr 21, 2018 at 0:24

When you spray the tiles, where does the water come from? If the shower's plumbing, the leak may be arising from feed lines junctions beneath the tile at the head or the faucet handle.

I'd start by spraying the tiles without using water from the shower's plumbing. Pour a few gallons of water from pails (filled elsewhere) onto the tile to confirm that the leak is not coming from the feed line plumbing.

Water also might be entering around the faucet cover plate or along the shower door seal. It's unlikely to be the grout in the tile field since the thinset should have sealed the tiles too well for any real water flow to occur. Sealing the grout would repel any water that much more.

I agree that the bottom most row of tiles could also be the source of leakage, if it wasn't sealed properly to the pan. But a close visual inspection ought to indicate gaps or misalignments. If it looks tight it probably is.

You might also want to temporarily tape a plastic sheet (e.g. garbage bag) over each suspected source of leakage before re-wetting the shower and looking for seepage. This may not seal perfectly but it should slow the leak enough to help you to exclude or confirm each possible source.

(Am I seeing things? In your picture #4, at the bottom right of the bottom-most right-most glass tile where the surround meets the pan... it looks like there's a small hole in the bottom corner of that tile.)

  • Thanks for yoir answer. If I just run the shower into multiple buckets then no leak occurs so it can't be the pipes or the waste... Is it impossible to be the grout?
    – Joe
    Feb 4, 2015 at 7:49
  • I'm not certain, but I wouldn't think the grout could leak appreciably. Many people forget to seal grout and AFAIK the only downside is the grout may discolor due to mold. No, I suspect the most likely cause has been suggested by others -- the lowest row of tiles probably isn't properly sealed to the pan.
    – Randy
    Feb 5, 2015 at 0:44

The basic requirement when two tiled/ceramic surfaces meet at an angle other than the same plane is to use silicone. Do not use grout as invariably there is movement which will crack the grout and allow water egress into other substrates and weaken them, which will give you a headache. Some things to check: Get a grout scraper and scrape the joints from about 4 or 5 feet up down to the tray to see if there are any gaps. If so, then re-grout using waterproof/flexible grout. If there are large gaps at the bottom then "Dob&Dab" may have been used to affix the tiles. In which case, remove the tiles and re-plaster and when dried re-tile. Sealing the bottom joint is best done by masking the tile and the shower tray to a spoons distance and "pushing" the bathroom silicone in the using a teaspoon, drag the waste out, smooth-off with wet finger, remove tape straight away and finally smooth-off again with wet finger. Perfect finish. When this has been done silicone the vertical corners but no need to use tape. One other thing. Have the frames for the glass panels been siliconed before they were screwed in place? Make sure. The skirting board/floor joint close to the shower should be siliconed also, This is a wet room. Tiling straight onto plasterboard however, is incorrect as the area has to be "Tanked" first. Kits are available for shower areas at all good DIY farms. The shower tray should be tight against the two walls as mentioned previously. Good luck

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