What is Tanking Damp?

Tanking damp is moisture moving through a wall where the tanking (vertical damp proof course) has been omitted or has deteriorated.

Causes of Tanking Damp

In the building process where soil is going to be placed against the wall and it is higher than the damp proof course, P.V.C. tanking should be placed between the soil and the wall. Should the P.V.C. have been incorrectly installed or have deteriorated, tanking damp will occur. In showers: 

Showers should be sealed during construction. Tiled walls are not water proof, because moisture can penetrate the joints between the tiles. Also raising the floor of the shower above the original damp proof course to make room for the shower trap can cause a breach of the damp proof course.