What Type of Damp Do I Have?
Rising damp, penetrating damp, condensation and below-ground damp all look similar on the wall, but each needs a different fix, and treating the wrong one wastes money. Answer six quick questions about what you're seeing and our free checker will tell you the most likely cause in under 60 seconds.
Answer 6 quick questions about what you're seeing and we'll tell you the most likely cause: rising damp, penetrating damp, condensation or below-ground damp.
This check gives a likely cause based on common symptoms, but damp problems often overlap, and the wrong treatment wastes money. Only a professional survey can confirm the diagnosis and the right fix.
✓ Your survey fee is deducted from the cost of works if you go ahead
Built by the specialists at Advanced Damp, trusted across London with hundreds of 5-star reviews. No email required, no obligation.
The Four Types of Damp Explained
Almost every damp problem in a UK home comes down to one of four causes. Here's how to tell them apart and why it matters for the repair.
Rising Damp
Ground moisture travelling up through walls by capillary action, usually because the damp proof course (DPC) has failed or been bridged by raised ground levels, render or debris in the cavity. Most common in pre-1940s solid-wall properties.
Tell-tale signs: a tide mark up to around 1 metre from the floor, white salty deposits, rotting skirting boards and bubbling plaster low down.
Rising damp treatment →Penetrating Damp
Rainwater forcing its way through the building fabric: defective gutters, downpipes, pointing, render, roof junctions or window seals. It tracks with the weather, getting worse during and after rain and easing in dry spells.
Tell-tale signs: isolated damp patches at any height that grow after rainfall, staining on ceilings or chimney breasts, and visible defects outside.
Penetrating damp repairs →Condensation & Black Mould
Moisture generated inside the home from cooking, showering and drying clothes, settling on cold surfaces. It's the most common form of damp in UK housing and the usual cause of black mould, especially in winter.
Tell-tale signs: water droplets on windows and cold walls, black mould in corners, behind furniture and around window reveals, and a musty smell.
Condensation & mould solutions →Below-Ground & Basement Damp
Lateral moisture pushing through basement and cellar walls from the surrounding earth. Standard damp treatments won't hold below ground. These spaces need a waterproofing system designed to BS 8102, such as tanking or a cavity drain membrane.
Tell-tale signs: damp or wet walls and floors below ground level, a persistent musty smell, and dampness that's constant rather than weather-dependent.
Basement waterproofing →Why the Right Diagnosis Matters
Damp is one of the most misdiagnosed problems in UK housing. Condensation gets treated as rising damp, penetrating damp gets painted over, and basements get patched with products that were never designed to hold back ground water. The result is the same wall being "fixed" two or three times, at the homeowner's cost each time.
The checker above gives you a well-informed starting point based on the symptoms you can see. But damp problems often overlap (a cold, damp wall caused by a failed DPC will also attract condensation, for example), which is why we always confirm the diagnosis with a professional survey before recommending any treatment. Our surveyors use moisture profiling, salts analysis and thermal imaging where needed to identify the true cause, not just the visible symptom.
And because we believe you shouldn't pay twice for the same answer, your survey fee is deducted from the cost of works if you go ahead with us.
Damp Checker FAQs
Common questions about identifying damp and what to do next.
How accurate is the online damp checker?
It's a well-informed starting point, not a survey. The checker uses the same symptom patterns our surveyors look for, such as location, appearance, timing and property type, to identify the most likely cause. But damp problems often overlap, and conditions like salt contamination or hidden leaks can only be confirmed on site. Treat the result as a likely diagnosis to be verified, never as a basis for buying treatments.
How do I tell the difference between rising damp and condensation?
Rising damp almost always shows as a tide mark or staining within about a metre of the floor on ground-floor walls, often with white salty deposits, and it's fairly constant year-round. Condensation shows higher up, in corners, around windows and behind furniture, usually as black mould rather than staining, and it's much worse in winter. If your problem is upstairs, it isn't rising damp.
Is black mould the same as damp?
Black mould is a symptom, not a cause. It grows where moisture settles on a surface, which in most homes means condensation, but it can also indicate an underlying damp problem keeping a wall cold and wet. Wiping mould away without fixing the moisture source means it returns. If mould keeps coming back in the same spot, the cause needs to be identified properly.
What does a professional damp survey involve?
Our surveyor inspects the property inside and out, profiles the moisture in affected walls, checks external defects, ground levels and ventilation, and uses salts analysis or thermal imaging where needed. You receive a written report identifying the cause and the recommended fix with costs. The survey fee is deducted from the cost of works if you proceed with us.
Can I treat damp myself?
Sometimes, if the cause is simple. Clearing a blocked gutter, lowering ground levels above a DPC or improving ventilation are all sensible first steps. What we'd caution against is buying tanking slurry, damp paint or DIY injection creams before the cause is confirmed: these products mask symptoms, can trap moisture in the wall, and often make a professional repair more expensive later.
Do you cover my area?
We work across London and the South East from our London office, with coverage extending to Buckinghamshire, Oxfordshire, Berkshire, Hertfordshire and the Midlands. Call 0300 373 7251 and we'll confirm coverage for your postcode.
Get the Diagnosis Confirmed
A professional damp survey identifies the true cause and the right fix, with a written report, clear costs and no pressure.
✓ Survey fee deducted from the cost of works if you proceedLearn more about our services: Damp Proofing in London · Basement Waterproofing London · Damp Surveys · Book a Survey