Many old buildings were built without d.p,c’s and, provided they are situated on dry, well drained sites, have no rising damp problems at all. Others on wetter sites have extensive problems.However rising damp resulting from a failed, defective or non existent d.p.c. is not restricted to old dwellings: with the advent of water- proofing solutions as additives to mortar, many cases have arisen of incorrect mixing of the additive and the subsequent failure of the d.p.c.
Old damp proof course are not impermeable and are often fractured by foundation movements in buildings. A sudden build up on hydrostatic pressure from leaking drain, or a raised street level may well cause a reasonable effective d.p.c. to fail.