Condensation damp: diagnosis and how it differs from rising damp
Condensation is the most misdiagnosed damp. Learn how to tell it apart from rising damp and infiltration, and what resolves it.
Thermography locates the cold surfaces where water vapour condenses.
The most misdiagnosed damp of all
Of all types of damp, condensation is the one most often misdiagnosed. It gets confused with infiltration or rising damp, ineffective treatments are applied, and the problem returns every winter. Understanding its origin is the first step to solving it.
Why condensation happens
Warm air holds more water vapour than cold air. When humid indoor air meets a cold surface —a poorly insulated wall, a thermal bridge, the edge of a floor slab— it cools, reaches its dew point, and the vapour turns into liquid water on that surface. That is why it appears in cold months, in corners, behind wardrobes and around windows.
There are two variants:
- Surface condensation: water appears on the inner face of the wall (stains, black mould).
- Interstitial condensation: it occurs inside the wall, between layers, and is harder to see but just as damaging.
Condensation, rising damp or infiltration: how to tell them apart
| Sign | Condensation | Rising damp | Infiltration |
|---|---|---|---|
| Where it appears | Cold spots, corners, windows | Base of walls (up to ~1.5 m) | Near the point of water entry |
| When | Cold months, worse with poor ventilation | Constant all year | Tied to rain or a leak |
| Look | Black mould, droplets | Efflorescence, low-level flaking | Stain spreading from a source |
This distinction is not academic: each origin has a different liability and a different solution. That is why our damp report always starts by identifying the cause with thermography and hygrometry before proposing anything.
Solutions that actually work
Condensation is not cured by painting with anti-damp products. Effective measures tackle the origin:
- Improve the insulation of the cold surface (remove the thermal bridge).
- Controlled ventilation to remove vapour (better than opening windows at random).
- Reduce indoor vapour production where possible.
- In complex cases, a hygrothermal analysis of the wall to size the solution.
When to request an assessment
If damp returns despite repairs, if there is a dispute about its origin (association, builder, defective insulation in a new build) or if you need evidence to make a claim, an independent report provides a documented cause.
Recurring mould every winter? Tell us about it and we will tell you whether it is condensation and how to resolve it.