Condensation or Penetrating Damp: How to Tell the Difference
"Is this condensation or damp?" is one of the questions we're asked most. They can look similar at first glance, but the fix is very different — so telling them apart matters.
Look at where it appears
Condensation typically shows up on cold, non-absorbent surfaces — windows, mirrors, cold external walls — often worst in winter and in rooms with less airflow, like bathrooms and bedrooms.
Penetrating damp usually appears near a specific source — under a window, around a chimney, near a roof valley — and tends to get worse in wet weather rather than cold weather.
Other clues
- Condensation is often accompanied by visible water droplets or a damp smell after showers or cooking
- Penetrating damp often leaves a tide mark, staining, or bubbling paint in one consistent spot
- Rising damp — a third possibility — usually stays within the first metre of a wall, near the floor
Why the difference matters
Condensation is usually managed with better ventilation and heating habits. Penetrating and rising damp are structural issues that need identifying and repairing at the source — no amount of ventilation will fix a leaking gutter.
Still not sure? A professional survey gives you a definitive answer rather than a guess.