12/12/2025
The widespread damp proofing scam.
One of the most common issues I see, particularly in older properties, is the unnecessary installation of chemical damp proof courses.
In many cases, damp companies either fail to assess the wider cause of moisture ingress or choose not to, because there is far more money to be made injecting a so called “solution” into the walls.
In the photo above, you can clearly see the original slate damp proof course, with a chemically injected DPC installed above it. The slate DPC has not failed. The real issue here is that external ground levels have been raised and are bridging it. Across much of this property, the ground level sits one to two bricks above the original slate DPC, allowing moisture to bypass it entirely.
Despite what many will tell you, slate damp proof courses do not fail. They are waterproof stone, sandwiched between bricks. There is nothing to degrade, dissolve, or “wear out”.
The correct remedy here was simple:
Reduce external ground levels by approximately 150–200mm
A straightforward, low cost fix.
But that does not generate thousands of pounds in revenue.
So instead, the homeowner is sold a £7,000 chemical injection system, which in situations like this often does absolutely nothing, because the underlying defect has not been addressed.
This is exactly why proper diagnosis matters. Damp is not a product problem, it is a building physics problem.
If you are dealing with damp, make sure the cause is identified before anyone starts selling you a solution.
