Damp under bay windows

[foxhole]

Thanks foxhole. I don't think it is condensation as they are double glazed windows, and I never see condensation o them. I note that damp is only on the bottom of the bay where it meets the wall in the interior. When I say it is on the corners of the bay, I mean that it is on the places circleed in the below image. It is exactly the same on the bay on the ground floor. The wall has lining paper. I removed the lining paper on the second from left circle, so I could see behind it. The plasterwork all seems okay apart from right at the top. I was considering hacking away some more plaster at the top and filling any visible holes with expandable foam. Any thoughts? The wall is a cavity wall.View attachment 357277

Double glazing doesn’t prevent condensation and you may not see it because it’s dripped off the corners onto the wall.

 

[opps]

Double glazing doesn’t prevent condensation and you may not see it because it’s dripped off the corners onto the wall.

True, but one would expect to see water pooling on the sills.