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Hello, very helpful people,
Need advice on troubleshooting the issue.
I had cavity walls insulated January 2021. By now I've noticed a damp line (?) appeared on one part of the ceiling, right above the landing, of all the places!
It might be a coincidence or it might be that insulation somehow triggered/revealed this issue. What I cannot figure out is - what place do I start to look at and which trade is best qualified to sort it out (Not talking about redecorating ceiling, but actually - to find the cause of the damp):

- Get the roofers to check the bottom rows of tiles for any leaks? (before the insulation the cavity walls were empty, so it might be that the leaking water was just sliding down inside?)
- Or should it be someone who understands the insulation

House built 1938, pitched roof with those awkward slopping ceilings around the perimeter. (I still cannot get my head around to understand how they came out like this - because of the roof incline or internal/external walls being uneven height or just fanciful design?! Very inconvenient and difficult to maintain!)

Loft insulated with blanket wool between the beams, about 70-100 mm, old, due to be updated. Current insulation was done about 20 years ago. From where I can see, it looks like being rolled to the roof rafters, but I'm not sure how to check if it needs to be tacked down into the space where the roof goes down (corresponding with the slopped ceiling from inside). What is the right way to insulate around such awkward places to make sure of the air flow ? and most importantly - whom should I be calling out for this - general builders, insulation companies or roofers?
Pictures of the damn line on the ceiling attached: Many thanks in advance! Would really appreciated advice on how to deal with this issue. Info on the internet is various and different approaches, none seems to match my situation precisely though. Looking forward for helpful tips.
Lana

Hard to say from pictures but that common rounded ceiling edge was how builders back then got room height extending into the of area of a low pitched roof line. The rafters will touch the highest part of the curve which looks like where the damp is. I suspect there is a defective tile that is allowing some moisture in and if you can crawl in the loftspace and have a look if you can see any defect in that area. I do not think it is related to the cavity wall insulation although it is possible a tile got moved slightly during the loft insulation laying. All guesswork.

DWD

The sloping soffit rafters (common rafters) are sitting on a wall plate on top of the vertical wall.
Installed Insulation should go down the soffit to the wall plate but a gap for ventilation should be left above the ventilation.

Lay on a board to examine and insulate the soffits - photos of what you see in the roof space above the leak will help, so will photos of the outside of the roof covering.

Thank you very much for both responses! Had to wait for weekend for a friend to come over to help me to examine. Frankly, I could not see any wet/damp spots inside the slop of the rafters/ceiling, but it goes way too deep down for me to see the very bottom of where the rafter sit on the wall, besides, the felt hides the back of the tiles :-/.

Also, in few spaces there are battens that looks like part of the lath and plaster ceiling (only without a plaster between them) that go over the edge of the flat ceiling and up to the sloping rafter, forming sort of grill over the cavity, so it is impossible to even inspect /insulate deep into the cavity. Oddly enough, these are not placed along the whole wall, but only in parts of it.:-/ The part where "grill" is missing, seems to be over the problem on the ceiling, but I was unable to get deep down enough to check if it is something at the bottom of the cavity, I am not sure how you'd insulate down the cavity of the slop. Also, a very old felt is deteriorated to the point, when touched, it dissolved into dust. The old insulation in the loft hasn't been touched since it was laid, around 10 years ago, however the ceiling line appeared only recently, last month or so. I was unable to see any obvious traces of the leaks from outside either.


Guess, will have to find a builder/roofer to come to inspect.
Once again, thank you very much for your helpful advice!
Lana.

It could just have been high wind blowing rain under the tile on one occasion. If there was a serious defect it would be getting worse. One thing to check is if the gutters are running freely as it might be slow moving and spilt over a bit. Have you access to ladders to have a check outside to suss out any issues?

DWD

DWD, thank you for prompt response!
myself, I am too afraid of heights to check the gutters myself, but I asked a kind neighbour to help me with this. I am hoping it may have been just a one off, like you said. But we didn't have much rains lately to double check this theory. Would you be able to advise on the best ways to insulate near eaves on the loft, as I will be adding extra layer this summer after a lockdown winter spent in a very chilly upstairs room :-( Is there a "diy" simple enough way to check walls humidity levels? (Is there such thing at all for the house of 1938?!) ? Probably, mostly, for my own peace of mind, really.
thank you again!
Lana.

The problem with these curved ceiling void areas is that there has to be an air gap to allow ventilation into the roof space which I believe the batten like grill is. Certainly, upping the insulation level in the loft will help with heat loss but this cold spot of the curved ceiling is difficult to reach. The solution might be too much work and mess to take on but that part of the ceiling could be pulled off and after inspection and any action for the water issue the void could be insulated and plasterboard fitted and slimmed over to finish. A lot of work for a small area and as the room looks straight not something you would take on readily. See if the neighbour can check the outside for you, sometimes it can be obvious when you can check things closely.

DWD