damp course 
(also damp-proof course)
noun British
A layer of waterproof material in the wall of a building near the ground, to prevent rising damp.An insulated concrete floor was laid, with a damp course up the walls and dry-lining downstairs....
- In recent years, Mr Parrett has become a leading expert in damp problems and says he has yet to encounter a true case of rising damp caused by the failure of an existing damp-proof course.
- In older houses check the pointing, particularly in courses of bricks below the damp course.