I have a damp patch, now about 2ft wide and 9ins deep, on an external stonebuilt gable wall (no insulation), appearing on plasterboard (not plastered). It started about 7 years ago and is slowly getting bigger. I think it may be a bridging issue. I can't see anything outside which would have caused it.
As an interim measure can I cut the plasterboard inside and clean it out? Realise that this won't solve the damp. Any advice please would be very gratefully received. Thank you!