These defects are not always evident but when they are, diagnosis is usually straight forward. When these defects are not present it may be necessary to carry out some destructive testing to establish the cause of the dampness.
Penetrating damp from defective gutters and down pipes, failed lead work or other common defects require investigation to determine the over all required remedial action.
Most types of masonry used in the walls of buildings will allow some water movement by capillary action; however, this is usually controlled by a physical barrier or damp proof course. If this physical barrier is absent, has broken down or is damaged then it is often possible to install a remedial damp proof course (DPC) to control water rising from the ground.
Water rising from the ground often introduces contaminating salts into the walls and plaster coats. This contamination will often result in a need for the plaster to be removed and replaced using specially formulated salt resistant plasters.