Damp pattern like this

[Clearheaded]

Has anyone ever seen a damp pattern like this, the room is north facing. It is further shaded by part of the building that extends beyond it.

the house was built in 1980 ish.

I uploaded a picture but I know they can be delayed in uploading due to need for review

I got someone to check the gutter was ok and you can see a vent

What is above the ceiling/ other side of the mould patch?

The attic, it is part of the old house (as in not the extension built in 2019). I went up the attic and it looked fine, but it corresponds to an area that isn’t floored so it is hard to investigate fully

If the gutter is ok, what about the roof?

i did look up the attic before and there was nothing I could see, but I was scared to walk on the beams right to the very narrow corner. By coincidence we had some significant storm damage in January and needed some tiles replaced. It was very unfortunate but the roofing guy had virtually no English. I wonder if the broken tiles were from before the storm ?

re the gutter, our neighbour who is an older lady isn’t quick to do maintenance on her property. Her gutters were drooping with debris and it was affecting water flow. I got a man out to clean both of them and he said that wasn’t the problem. I did wonder if he said that because he didn’t want to cause drama between neighbours… I understand why a tradesman wouldn’t want that grief. Also the neighbour is a wonderful kind older lady.

We had a new roof and when the reallynheavy rain fell we thought we saw damp, but it went, this happened a few times and it turned out one of the roof tiles was slightly out of place, it completely stopped. We didn't get mould, just water marks so it doesn't really look like your photo, but worth a check of the tiles nearby

It’s possible your insulation doesn’t go up to the edges.

Thanks for all the comments. Definitely some good ideas