We had recently treated an old terraced house for rising damp. The house was built in 1910, so had solid 9″ walls and no physical DPC. The damp was only showing on half of the downstairs walls within the property, and as such the owner requested that rather than treating all the walls fully, we only treat the walls that are showing as being damp.
We suggested that it might be better to treat all the walls at the same time, even the ones that weren’t showing as damp, but the owner told us not to bother and to only concenrate on the walls that were damp. We duly stripped off the damp plaster to the recommended 1.2m height, injected the walls with a chemical DPC, and rendered the walls using a waterproof additive in the scratch coat.
After the skim was done and new skirting was put on downstairs, the finished job looked very good.
Fastforward a year, and the walls we hadn’t treated were showing signs of rising damp, which meant that the remaining walls had to be stripped off, injected and rendered to solve the problem. Basically, we had to go in a second time and cause a lot of disruption and mess to remedy a problem that could have been fixed in one go a year ago. The lesson for us was that no matter if only a few walls are showing signs of rising damp, all the walls should be treated the same, because once the damp starts showing up, it will end up spreading to the rest of the walls eventually.