I'm about to tile a shower alcove. However, I put a straight edge against the walls and the rear wall bows out very badly. The wall is 950mm wide and putting a straight edge across shows a gap about 8mm at it's max in the centre - i.e. big enough to get my finger through! I'm using 500mm wide tiles (by 250mm high) in a brick pattern. I did have a go at tiling it as is and just putting the tile adhesive on quite thick in the centre of the wall to try and fill out the gap a bit, but it looked awful so I've taken the tiles off.

The wall itself is a plastered external brick wall. The house is 1930s. I live in the UK.

Please could you advise what would be best to fix the issue to give a flat surface to tile on to? I was thinking of getting some ready mix plaster and spreading it on to level the gap - i.e. I'd spread it about 8mm deep in the centre and feather it out to 0mm at the edges, using a straight edge to check as I go. I wouldn't attempt this myself if the plaster would be the finished surface, but I think I can do a decent enough job given it will just be tiled over. Does that sound sensible and if so:

  • what type of plaster should I use?
  • do I need to prep the wall in any way before plastering? I've already painted on the primer the tile shop sold me that was to prep it in advance of applying the tile adhesive (I think this is just some sort of glorified PVA).
  • "Plaster" is bad --- this is a shower, and you don't want anything that will break down with moisture. Tile adhesive ("thinset" in the US) is what you want.
    – Paul Price
    May 28, 2018 at 18:57

2 Answers 2


Just in case this helps anyone, I spoke to the people at the tile shop and they recommended building the wall out using cement based tile adhesive (the type you buy as powder and mix). I did this and it worked well. You have to work fast though, that stuff dries very quickly!

  • I am not saying this can't be done and I guess something has to be done for severally bowed walls. But putting a skim of coat of anything on your walls has two issues. #1 being if that doesn't adhere or stay bonded you have issues down the road. #2 Putting a skim coat of concrete on flat is a craft and skill I don't think hardly anyone has. I just see this causing more issues.
    – DMoore
    Aug 27, 2014 at 17:05

I can't tell you how much I would be reamed if I plastered a brick wall, then painted it then put tiles on with adhesive for a shower. First that wouldn't pass any inspections in the US. I am not going to go on about how your shower should have been done or waterproofing because that is a different question.

Your answer is that you would deal with bowed walls by using thinset on your tiles. You would simply use more thinset on the parts that are in more and less on the bowed areas. I cannot tell you the last time I tiled a perfectly flat shower and unless you are using mosaics or really small tiles you will have to vary your thinset application to fix any issues.

  • I think this might just be a case of different terminology. I think what we call tile adhesive in the UK is what you are referring to as thinset - the stuff you apply to the wall with a trowel (or to the back of the tiles) and set the tiles into. Therefore I think your suggestion is actually what I did: build up the thickness of thinset where the wall bowed.
    – Kate
    Aug 28, 2014 at 13:24

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