To fix damp walls permanently, first identify the type of damp — rising, penetrating or condensation — then correct that specific cause and treat the wall with the right coating. A coating alone never fixes damp; it seals the wall after the water source is stopped. Rising damp needs a damp-proof course, penetrating damp needs the exterior sealed with Shield, and condensation needs ventilation plus Damp Proof.
The three types of damp — how to tell them apart
- Rising damp. A tide mark up to about 1 metre (m) from the floor, with salt staining. Moisture rises from the ground through a failed or missing damp-proof course.
- Penetrating damp. Patches that appear after rain, often mid-wall or near a crack, gutter or window. Water crosses the wall from outside.
- Condensation. Surface moisture and black mould in corners, behind furniture and in bathrooms, worst in cold weather. Warm moist air meets a cold wall.
How to permanently fix damp walls
Fix the cause that matches the damp type, then seal the wall. Rising damp needs a new chemical damp-proof course and re-plastering with a salt-retardant mix. Penetrating damp needs the external wall sealed — coat it with Shield and repair the crack, gutter or flashing that let water in. Condensation needs better ventilation and heating, plus a mould-resistant interior coat. Skipping the cause and only painting guarantees the damp returns.
How to dry out a damp wall
Once the source is fixed, let the wall dry fully before coating — a stripped wall can take weeks to dry, roughly 25 millimetres (mm) of wall thickness per month. Improve airflow, use a dehumidifier in closed rooms, and do not seal the surface until it reads dry, or the coating traps the remaining moisture and blisters.
Treating damp walls before painting
Before repainting, strip blown plaster back to sound substrate, treat mould and salt staining, let the wall dry, prime bare plaster with Solvent Plaster Primer, then apply Damp Proof and your finish coat. This sequence stops the damp reaching the new paint.
Frequently asked questions
How do I permanently fix damp walls? Identify the damp type, correct its cause — damp-proof course for rising, exterior sealing for penetrating, ventilation for condensation — then dry and coat the wall.
What is the best way to dry out damp walls? Fix the source, then improve airflow and use a dehumidifier. Allow roughly 25 mm of wall thickness a month to dry before sealing.
Where to buy
Shop Damp Proof and Shield, or read the complete waterproofing guide. Trade pricing: +27 84 985 6141.
