Hi, I live in a semi detatched house both myself and my neighbour have damp on our chimney breast cheeks the whole length of the cheeks but not on the party wall! The houses were built in 1930 and our ex local authority. We have a lead water main which goes from the road under my living room floor to my kitchen and tee,s off under my house to next doors kitchen!! Its only both fireplace cheeks in both properties that are affected and not the party wall . Any ideas ??
Stoneyboy is right but once the source has been fixed you need to dry the wall otherwise you will have mould or condensation problems in other parts of the house for some months especially during the winter.