Problems with damp
Damp can damage much more than a buildings appearance. It may lead to the deterioration of plaster and masonry, promote timber decay and create unhealthy conditions for occupants.
Unfortunately, inappropriate treatments for damp commonly cause greater harm to old buildings than centuries of degradation. Over-reliance on electrical moisture meters frequently leads to unnecessary expense and damage through the retrospective installation in walls of horizontal damp proof barriers (damp proof courses or DPCs). Equally the harm done by modern solutions that aim to seal old walls rather than improve their ability to breathe is underestimated.
An appreciation of how the basic construction of old buildings differs from that of new ones will help you avoid such misguided remedies.