I recently started having a lot of moisture in room next to my bathroom/shower wall. Its important to add that these walls are made of plaster.

Initially I thought it was the silicone than joins the shower with the wall that was letting water pass. The shower base started separating from the silicone.

I put new silicone but there is still moisture in the room. It's not a perfect job but it should be enough to keep water out. Or at least prevent that level of moisture.

I am now starting to think that the tiles joints may let water pass. These are 3 mm joints with bitumen.

My question is: what can I do? is it possible that the joints let moisture pass? Can I do something to isolate better the area with silicone? Is there something I can put on the joints? Any other tips?

  • 3
    Is there a vent in the bathroom and if so are you sure it's venting properly? Is the drywall moisture resistant? Commented Oct 20, 2013 at 15:15
  • @SpectralGhost I think I am venting the bathroom well enough. Drywall moisture resistant? I am sorry but what does that mean?
    – nsn
    Commented Oct 20, 2013 at 15:49
  • pladur=drywall, right? There are various types of drywall that are engineered with different properties. Generally, water resistant drywall is used in bathrooms. Are you sure the vent is venting to the exterior of your house? Commented Oct 20, 2013 at 17:24
  • @SpectralGhost - sorry, I didn't know that name for it. I think I am venting enough.
    – nsn
    Commented Oct 20, 2013 at 17:45
  • 1
    I'd consider whether the water could be coming from a leaking pipe too. You need to get to the source of the water, so you might take out some of the lower tiles, or cut out an area at the base of the adjoining wall (where it's wettest).
    – getterdun
    Commented Oct 21, 2013 at 3:21

1 Answer 1


Yes, the tile joints do let water pass. The grout is porous, and additionally does not seal tight with the tiles as it ages (causing it to actually pull some water in via capillary action). Many tile materials are not waterproof either.

Bathroom tiling is only "waterproof" in the sense that it is a finish material that will not be damaged by water. It does not serve to create a waterproof enclosure; that needs to be built behind the tile. If that was not done correctly, any attempts to seal the grout and tile will at best only serve to delay the inevitable.

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