How to Stop Damp on Internal Walls

Damp on an internal wall is frustrating — but fixable, once you know which type you’re dealing with and treat the cause, not just the symptom.

Here’s a practical, step-by-step guide to stopping damp on internal walls.

1. Identify the type of damp

Start by working out whether it’s rising damp, penetrating damp or condensation. A tide mark low down points to rising damp; growing patches after rain mean penetrating damp; mould high on cold walls means condensation.

2. Fix rising damp

Stop ground moisture tracking up the wall with a liquid damp proof membrane, applied at the base of the wall before re-plastering.

3. Fix penetrating damp

Make the external face raintight but breathable with a weatherproof brick sealer, and protect internal faces with a liquid waterproof membrane such as The GOAT. Browse the full liquid waterproof membrane range.

4. Fix condensation

Improve ventilation, remove cold spots, and add a continuous airtight, breathable layer such as Passive Purple® or paintable Airtight White to warm surfaces and control vapour. More in our guide to condensation on walls.

5. Re-decorate properly

Only re-plaster and paint once the cause is treated and the wall has dried out — otherwise the damp simply returns through the new finish.

For the bigger picture, read what causes damp walls. Need a hand choosing products? Contact us today.