What Type of Damp Do I Have?
Mould in the corners, a tide mark on the wall, a patch that grows when it rains, they all look like "damp", but they have different causes and completely different fixes. Answer a few quick questions to find the most likely cause and what to do next.
Answer based on what you can actually see and when you notice it. If you're between options, pick the closest, you can go back at any point.
What type of damp do I have?
Why getting the diagnosis right matters more than the treatment
"Damp" isn't one problem. Condensation, penetrating damp, rising damp, hidden leaks and below-ground moisture all stain walls and grow mould, but each has a different cause and a completely different fix. Improve ventilation when the real issue is a leaking downpipe and the wall stays wet. Inject a chemical damp proof course when the real issue is condensation and you've spent four figures on nothing.
That's why the order of operations matters: diagnose first, with evidence, then treat. It's also why we built this checker to tell you the most likely cause rather than to sell you a particular treatment, and why every result, whatever it says, ends the same way: a proper inspection confirms the cause before money is spent on works.
The main types of damp at a glance
Already finished the checker? Here's the quick reference for all of them, including the signs that point each way.
Condensation & mould
Airborne moisture settling on cold surfaces. Peaks in winter, loves poor ventilation.
- Black spot mould in corners, behind furniture, around windows
- Steamed-up or dripping windows on cold mornings
- Worse in winter, better in summer
Penetrating damp
Rain getting in through defects: gutters, pointing, render, roofs and chimneys.
- Patches that appear or darken during and after rain
- Can show at any height, including ceilings and chimney breasts
- Often maps to a visible defect outside
Rising damp
Ground moisture rising through walls where a damp proof course has failed, or, very often, been bridged.
- A constant band of damp in the bottom metre of ground-floor walls
- Tide marks, white salty deposits, crumbling plaster or skirting
- Doesn't change much with the weather
Hidden leaks
Plumbing, heating and waste leaks that soak the fabric slowly and constantly.
- A patch that never dries, whatever the weather
- Near bathrooms, kitchens, radiators or pipe runs
- Boiler losing pressure, or a water bill creeping up
Two special cases behave differently again: basement and cellar damp has its own specialist standard, see the below-ground guidance, and damp on old chimney breasts is often hygroscopic salt contamination, one of the most misdiagnosed problems in older homes.
When you're ready for a proper diagnosis
Every specialist on the Federation of Damp register is certified, vetted and accountable to our standards, which means evidence-led surveys, not sales-led ones. Search the register, or tell us what you need and we'll point you to the right specialist.
