Mould, blistering paint and damp and cracking plaster. What is the cause, rising damp or Leaky building Syndrome?

While rising damp was a big issue in older inner city houses it’s not common in modern housing. Old housing stock used slate as a water barrier between the courses of bricks in the lower part of the wall. The slate was used to prevent water rising up through the walls by osmotic pressure. Brick work is porous and soaks up water, much like a sponge. This is a well known problem in the building industry but the use of slate in older constructions was not a good solution in the long term.

Since then a number of better solutions have been found. Modern houses have a damp proof course. This is a waterproof layer, often using a high quality metal or plastic, which does not break down over time. Although not all of these solutions are fool-proof most modern houses won’t have a rising damp issue.

That being said most people associate the tell-tale signs of Leaky Building Syndrome with rising damp. In most cases the problem is not water rising up but actually water entering the wall cavity from above, and not being properly ventilated or drained. It’s also possible the flashing which is installed to drain this water out through the weep holes was not installed properly.

Although the damage is visible low down on the wall the problem is often a faulty gutter, roof leak or incorrectly installed air conditioner higher up in the wall. Using an Infra Red camera is the best way to diagnose where a leak is coming from, and many building inspectors now own one. Checking the roof and gutters is the most basic step you can take before calling a professional.