Wondered if anyone could please help as I'm completely baffled about a damp patch thay has carried on for years and 3 roofers have failed to make go away. My first questions is, if there were originally small penetrating leaks around 2 chimneys, but the problem was fixed, is it possible those areas that got damps would still attract the most condensation if they hadn't quite 100% dried out?
We have a room within the roof which has 2 chimney breasts going down through it. When it rains the wallpaper around the chimney breast just below the ceiling looks a bit darker and feels a bit greasy. But it also extends up and along the wall just below the ceiling for perhaps a couple of feet to the side of the breasts as well. This suggests it can't just be condensation attracted to a colder chimney breast. Also the entire length of the wall isn't bad so I don't think it’s just condensation on a cold outside wall (which isn't a cavity wall) or surely the whole wall would look similarly damp if it was condensation? It also extends a bit to the ceiling which is very slightly yellow near the chimneys, but above the ceiling there's about 6 inches of roof void which I guess is a bit warmer than outside even though there's no insulation . Originally we thought it was a minor leak associated with the chimneys so roofers twice went up and improved the pointing of the bricks. They thought the lead flashing and back gutter looked OK, but they never took it apart (when they lifted one bit there was a soaker). But the damp seemed to recur, so they discovered a gap of a few inches along the verge between the top of the brick wall and slates so they filled that in just in case wind was driving the rain in through the gap and running down to hit the chimney breasts. We also had 10 more air vents put in the roof.
Things have improved, but those patches still look wetter and feel greasier wjhen it rains. When we had a carpet clean and they forgot to open windows those patches did look the wettest which made me wonder whether they attract more condensation because they were once damp because of a possible resolved leak. But this seems to contradict the fact that even when no-one was using the room, those patches still looked damp after rain. Cold dry weather doesn’t seem to affect it, suggesting it’s nothing to do with hot and cold surfaces attracting condensation.
go into the loft, clear the area around the chimney breast, fill in any gaps around the base of the breast, where the ceiling meets, with expanding foam, then when its set lay insulation over the top, this will stop the cold spot which I think is causing condensation to occur.
Thanks Welsh Brickie, but you can't get in the loft because the room is in the roof space as you can see in the internal photo. (which also shows the damp patches, although the bit on the ceiling by the breast isn't too clear) There's only a few inches between the slates/felt and the ceiling plasterboard. I've also attached a photo of the chimney outside in case it shows any obvious reasons why water may be getting in.
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