DIY Doctor UK DIY Forums

I have had my downstairs fireplace plasterboarded, and I now have damp across the top section and the back and one side of the fireplace.
Water is obviously coming from above somehow.
Both Chimneys are capped, it has been repointed, the leading checked and there is ventilation in the top of the fireplace and on the chimney.
Multiple roofers have checked and said there is no way water is getting in from the top.
It seems to get worse when it rains although not when it is very cold outside.
There used to be a gas fire which I had removed, but the metal flue is still in place.
Could condensation be forming on the metal flue and then running down and dripping onto the plasterboard?
What other possibilities are there?

Thanks for your help.

Hi bencad,
The metal flue may be one part of the problem, the chimney will only be single skin so rainwater penetration is possible. If the damp is showing as a brown stain water ingress from the top is most likely.
Regards S