How can I tell if a dampness problem in my home has been caused by cavity wall insulation?

The first clue will be in the timing. If you have lived in your home for a few years and never noticed any dampness problems, but then had CWI installed and dampness problems start after that, then it is quite probable that you have cavity wall problems.

If the dampness if most evident on a south-facing or west-facing wall (one that gets the most wind-driven rain), then it is likely that the CWI is allowing rainwater to track across the cavity. The only way to be sure that this is the case is to get a builder or RICS Surveyor to inspect the inside of the cavity. This can be done by drilling holes in the outside brickwork in the suspect areas and looking through boroscope – an optical probe. This will often reveal damp CWI, debris, and voids. If the boroscope inspection doesn’t work, then it might be necessary to remove a few bricks and physically pull out a handful of the insulating material.