I had nearly identical damp caused by two issues - damp coming from the roof down through the walls to the bottom of the house (yep) AND cavity wall to outside of house filling up with debris/crap and allowing damp to pass in at ground level from outside.
Paid someone to treat it by injecting a damp proof foam into cavity wall. Been fine since.
Get a damp proofer to come and investigate and they can tell you. It's money well spent.
DaftVader t1_iun7hfr wrote
Reply to What is causing the damp on interior walls? by victor0nl1n3
I had nearly identical damp caused by two issues - damp coming from the roof down through the walls to the bottom of the house (yep) AND cavity wall to outside of house filling up with debris/crap and allowing damp to pass in at ground level from outside.
Paid someone to treat it by injecting a damp proof foam into cavity wall. Been fine since.
Get a damp proofer to come and investigate and they can tell you. It's money well spent.