Damp Proof Courses

A damp proof course is not a guarantee your house will be dry.  This is not because there is a vast lake of water underneath every house, just waiting to bubble up and flood the walls if that damp course is not there.  It's because 99% - yes nearly ALL damp problems - are nothing to do with moisture from the ground.  The most common cause of so called 'rising damp' symptoms is condensation - moisture that we humans produce within a building.  We breathe out several litres of water a day. We cook, we shower - we flood our homes with moisture - yet we just assume it magically disappears.  It doesn't - it ends up in the walls, the floors, the timber - and then you get the symptoms which the local Property Care Association 'timber and damp' contractor gleefully 'diagnoses' as rising damp.  We use the word in inverted commas, because these people are untrained, unqualified monkeys with absolutely no formal education into the science behind moisture, its transport mechanisms, and its causes.  

There is a lot more detail of this on the pages of this site: Managing Damp in Old Buildings

A damp proofing course is often specified in Building Regulations.  It is interesting to note that Building Regs are more interested in 'moisture mitigation'.  In Holland for example, damp courses are not even specified.