Porous tile grout?

[A.Lee]

I've got a strange problem with a customer I have had dealings with. It is a tenant, and I am working for the landlord. The tenant is rather difficult to get on with, and tends to exaggerate the problems in the house. Anyway, they have a combined shower/toilet downstairs, which has been crudely converted into a 'wet room', i.e., when you have a shower, everywhere gets wet, and is meant to drain into a central drain in the middle of the floor.

I got a call saying there is a water leak, and the floor is soaking in the kitchen, outside the room. I went, sure enough there is water damage showing, so I ran the shower for 10 minutes or so, but could find no leak. The tenant insisted that it was running through the wall (single breeze block, tiled in the shower, painted plaster on the outside). I check all the edges/joins and grout lines for cracks etc, but all looked well. Also checked all water pipes everywhere, no leaks at all. I put it down to splashing over the door, running down, and leaking over the poor quality, unsealed door threshold.

So I sealed up around the door. Got a call a week later, it is still leaking. This time there was evidence of a water leak, half way up the outside on the room. So it seems she wasnt exaggerating when she said it was coming through the wall. Check again the interior. No crack or gaps in the grout. So I'm stumped. Ok, it must be leaking somewhere, so I got the go ahead to get out the old grout and redo it. The old grout was rather strange, in that it was slightly damp, with a chalk like appearance when scraped out. My query - could the leak be caused by the water leeching through this grout? I thought all grouts were waterproof, or have I been misinformed?

Ta Alan.

[Dave Plowman (News)]

My guess would be movement causing the grout to crack. If the movement isn't too great an epoxy grout should sort it.

[Slider]

Ideally you need to tank the walls before tiling. Whoever tiled the walls in the so-called wet room did not know what they were doing. Ideally, all tiles will need to be removed, the walls tanked, then re-tiling with the appropriate adhesive and grout.

[leenowell]

My brother in law had exactly the same problem and it turned out the grout was not waterproof he had to get the whole lot done again. His was done by a professional tiler so I'm not sure whether he used the wrong grout (would seem a school boy error for a professional) or whether the batch he used was faulty. As they were not sure the source until they started ripping out the shower (thought it was a pipe leaking somewhere), the insurance company paid for the investigation and remediation.

[Andrew Gabriel]

Epoxy grout is waterproof, but I don't think it will cope with any movement at all.

You can make ordinary grout waterproof by adding a waterproofer/plasticiser to it, such as BAL addmix GT1. I do this in showers, because it also seems to prevent the grout getting dirty -- if it's waterproof, dirt can't get into it, and that theory has worked perfectly on two showers I've done so far. The BAL addmix GT1 is expensive, but a little goes a long way.