For those of a certain vintage, Rising Damp was a classic 1970s comedy. But in the world of property maintenance, the title has become something of an urban legend.
Most people see black mold—which is almost always condensation—and immediately cry “rising damp!”
The industry has leaned into this fear. If you call a damp-proofing company, don’t be surprised when they suggest a damp-proof course (DPC). After all, if you’re a hammer, every problem looks like a nail. Or in this case, every wall looks like it needs an injection.
The Great Brick Myth
Let’s look at the basic science. Many contractors will tell you they need to inject your bricks with silicone or chemicals.
Here is the reality: you cannot inject a traditional clay brick.
Think about it. If bricks were truly porous enough to be “injected” like a sponge, they would absorb every drop of British rain. When the first frost hit, that water would expand, the bricks would shatter, and our houses would crumble into dust. Bricks are designed to shed water, not soak it up. If you drill a hole in a brick and try to inject it under pressure, nothing happens. The physics just don’t work.
The “Sand and Cement” Mask
What often happens is the contractor applies a sand-and-cement render with a waterproof additive. This creates a closed-cell construction. While this might hide the moisture for a while, it doesn’t actually fix the source. It just traps the dampness behind a hard shell. Eventually, that moisture will find a way out—usually by spreading even higher up the wall, above the new plaster line.
Finding the Real Culprit
In the vast majority of cases, “damp” isn’t a mysterious force rising from the earth; it’s a maintenance issue. Before you spend thousands on chemical injections, look for the source of moisture:
• Leaking Gutters: The #1 common offender.
• Ground Levels: Is your garden path or driveway sitting above the original DPC?
• Splash Zones: In places like York city centre, cars driving through puddles can spray constant moisture onto roadside masonry.
• Defective Pointing: Cracks in the mortar allow driving rain to seep in.
• Hygroscopic Salts: Using the wrong plaster (or sticking plasterboard directly to a solid wall) can actually pull moisture out of the air.
The Surveyor vs. The Salesman
Here is the golden rule: A damp-proofing contractor sells damp-proof systems. They have a financial incentive to find a problem their product can “solve.”
A Chartered Building Surveyor, however, sells expertise. A surveyor doesn’t have a crew waiting in a van with a drill and a bucket of silicone. They will identify the actual defect—be it a blocked downpipe or a high flowerbed—and fix the root cause.
The Verdict: Don’t pay for a “system” until you’ve paid for a proper diagnosis. It might cost you a surveyor’s fee up front, but it will save you thousands in unnecessary “injections” that the science simply doesn’t support.