Have a house ~1870, which is having some leaking/damp issues. One place I'm looking is where the neighbours boundary wall meets the corner of our house. Our house is on the left.

It's difficult to see how well it's joined due to the small angle between the two. I've tried filling some cracks I can reach, and painting the wall (builders suggestion, but still water coming through) as far as I can with an extended roller, but the actual join between the two is pretty messy and I suspect prone to letting in water, but I can't physically reach it as it's too narrow.

It's a bit of a strange wall, as the boundary wall almost seems to cut into the house wall. Near the top there seems to be grouting missing.

Ignore the bits of wood, I added them yesterday, just temp to see if I could deflect some water from running down the join.

I'm a bit stuck with where to go with this, builders don't seem to want to know. Is there any way to make that good, or would it be worth trying to make some cover over the angle to try and deter water from hitting that area ?

Pic1 Pic2

Near the top, there isn't grouting also.


Inside, the darker damp spot and the corner jutting in, is about where the join between the walls is. (We had a builder come in, take it all back and put some stuff in there to help prevent it and thought it looked ok after filling/painting the outside wall, but it's still still coming through). The dark wet patch kinda lines up heightwise with the outside vent, but at the join, but naturally it could be coming in elsewhere and trickling down to that patch.


This is when it was "taken back" (not sure what the term is!), we wondered whether there used to be an old window lintel or something in there.

before plaster

  • Can you separate the two?
    – Solar Mike
    Nov 16, 2022 at 10:13
  • No, I don't think that's possible at all. It's very strange the boundary wall actually seems to cut into the house wall, and continues on the other side of the house cut in also (but access ok on the other side of the house).
    – Ian
    Nov 16, 2022 at 10:25
  • Sounds like your house was built over the property line?
    – SteveSh
    Nov 16, 2022 at 11:36
  • 1
    Or the other house was built over the property line. What does that corner of the house look like from the inside? Normally, the recommendation is to waterproof from the outside, then repair the inside, but an alternate may be called for here - can you approach the waterproofing from the inside at all?
    – FreeMan
    Nov 16, 2022 at 12:17
  • 1
    Nice, thanks. What's behind the interior finish? Is it a brick wall, wood framing, something else? I presume you got a look at it when the builder "took it back".
    – FreeMan
    Nov 16, 2022 at 12:43


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