Problems
Condensation vs rising damp: how to tell them apart
These three issues look similar to the eye but have different causes, fixes and costs. The right first step depends on telling them apart.
The key difference
Condensation is airborne moisture meeting a cold surface. Rising damp is ground moisture travelling up through walls via capillary action. Penetrating damp is water entering from outside through a defect.
One is a humidity and ventilation problem. The others are building-fabric problems.
How to identify condensation
- Tide marks or droplets on windows, especially mornings in winter
- Mould in cold corners, behind furniture on external walls, and around window reveals
- Worse in winter and in rooms where moisture is produced (kitchens, bathrooms, bedrooms)
- Walls feel cold but not visibly wet to the touch
How to identify rising damp
- A horizontal tide mark roughly 1 metre up the wall
- Salt deposits (white fluffy crystals) on plaster
- Wallpaper peeling or bubbling near the skirting
- Skirting boards rotting at the base
- Almost always on ground-floor external walls
What penetrating damp looks like
- Patches that appear or worsen during and after heavy rain
- Usually on or near external walls, around windows, or below a defective gutter
- Damp patches with a defined edge rather than a gradient
Which needs a professional
Condensation can often be improved with ventilation and heating habits. Rising damp almost always needs a qualified independent surveyor — not a 'free survey' from a damp-proofing contractor. Penetrating damp needs the source defect found and repaired first; treatment alone won't fix it.
Upload photos for an assessment