Parapet wall ingress from neighbour

[Diver Fred]

I'm not a roofer by any means but have have done roof repairs and reroofed a couple of extensions. So what do I see from your 'photos,
Neighbours side :-
On the pitched roof the Lead work is wrong; there should be 'Soakers' on each course of tiles Lead should not be over tiles. The roofer has cut the Step flashing in nicely so seems strange that he laid the lead over the tiles instead of using soakers. Without soakers water will track sideways and into the wall. See

The Leadwork (in my mind) should go all the way up to the ridge underlapping the tiles on your side on your side as well, rather than the mortar fillet.
Your side :-
Why or what is over the bottom course of visible tiles? The trough should have been put in place first - on the roof side to at least to top of the rafters/sprokets and the same height on the parapet wall. On the parapet wall it should then have been flashed over by at least one more course of bricks. On the roof side there should then be drip trays (Eves protector tray) or more lead over the trough lead but under the bottom (1/2) course of tiles.

If there is as I suspect, a drip sheet over the tiles on your side I'd say that is the cause of the damp.

 

[Gas man]

No it’s external only shorter than neighbour , end of wall will get soaked during rain and can’t see what’s under lead but could be likely source of ingress if not dressed correctly .Was lead work done by same people , looks inferior on your side?

Hi there

I agree the lead on my side doesn’t look tidy but I had my sides roof redone with rubber underneath. So that’s the original roof done 3 years ago and then another roofer redone all that part 2 years ago.

My neighbour built the wall between his house and mine and also between his house and the other side of his house and you can see what he’s done there I have just noticed this, he has covered the wall with felt so it just reinforces the Belief there’s an issue with the wall taking water. In winter The wall is soaked to the touch even after no rain for days however in summer it’s ok as it dries out fast and there’s never any sign of the damp in summer only winter

 

[catlad]

So Your neighbour built an extension and insisted on a parapet wall?

 

[Gas man]

3 houses built extensions at the same time and the design was for a parapet wall between them. He own the other 2 houses, the middle and far end. He insisted on doing his own extension and both parapet walls. The fact he’s completely covered the parapet wall between his 2 houses with felt confirms my believe it’s the wall that the issue as his roofers came back multiple times and I believe refused to come back any more as it’s the wall that’s the problem. It’s really hard to show from pics but my side it seems like the damp is coming through the bricks/mortar. I believe if it was covered with lead the issue would go away. My house is the highest point and the damp is coming through from the cement line on his pitch where it comes down to the new extension roof

 

[Diver Fred]

Is image 6588 your roof or his?