The Public Health Act of 1875 requires that a damp proof course is installed in all dwellings. Unfortunately DPCs break down with age. The major of pathways through which the water rises up a wall are the mortar joints. In effect, the mortar joints form the only continuous pathways for water rising through the wall.

Damp 1Damp 2

If a house is built from impervious brick then water can still rise up through the mortar joints.  Even though rising damp can be controlled by the insertion of a remedial damp proof course, the salts in the plaster will remain. It is important to remove and replace the contaminated wall plaster with a new sand and cement render containing a water proofer/salt inhibitor in addition to the insertion of a damp proof course.