Preparation & Problems
Damp Walls Before Painting: What to Do First
Why damp must be fixed before painting, possible sources and who may need to assess them, why anti-damp paint isn't a fix, and drying out before you decorate.
- Evidence reviewed
- October 2026
- Surface methodology
- FGS-1
A damp wall is not ready for paint. Painting over damp doesn't fix it, and paint applied over moisture tends to blister, peel or discolour early. The first job is finding and fixing where the water is coming from.
Fix the cause before decorating
Every credible source agrees on the order: resolve the cause of damp before decorating. Kenyan manufacturers' guidance says the same, including for their own anti-damp products. Until the source is fixed and the wall has dried, the damp area is on hold.
Possible sources, and who may need to look
Where damp appears gives a clue about who should look at it. These are possibilities to rule in or out, not a diagnosis: identifying the cause needs someone on site.
| Where you see it | Possibility to rule out | Who may need to look |
|---|---|---|
| Near bathrooms, kitchens or pipe runs | A plumbing leak from pipes or tile joints | A plumber, to find and repair the leak first |
| Near the bottom of ground-floor walls | Moisture from the ground, which may need damp-proofing and re-plastering rather than paint | A damp-proofing or waterproofing specialist, or a building professional |
| Below a roof or terrace, or on an outside wall | Water getting in from outside | A roofing or waterproofing specialist: lasting waterproofing, as patch repairs tend to give only temporary relief |
| Anywhere else, or you're not sure | Unknown | A professional assessment before anything is quoted |
A painter is the right person once the source has been fixed and the wall has dried.
Anti-damp coatings are not a fix
Anti-damp and moisture-resistant coatings have their uses, but they are not a replacement for fixing the underlying cause. Kenyan manufacturers say so about their own products. Coating over an active source only hides it for a while.
White salty deposits
White, powdery salt deposits on a wall (efflorescence) are a sign of moisture moving through it and are worth investigating. Don't coat over them.
How far the problem reaches
Moisture often reaches beyond the patch you can see, and treatment may need to extend well beyond it. How far is decided on site; FinishGrid doesn't apply a fixed margin. If one cause could affect several walls, such as a roof leak above several rooms or damp along a ground floor, treat all of those areas as on hold.
Let the wall dry, then prepare it
After the source is fixed, the wall needs to dry out before it is prepared and painted. How long that takes depends on the wall and the conditions. Then check the surface again: damp can leave paint loose or plaster damaged, which needs preparing like any other defect. See Why Is My Paint Peeling? if the paint has been peeling.
Planning the rest of the project
A damp area doesn't stop you planning areas that are ready. Plan those, leave the damp area out, and remember that a room is often painted in one go, so one held wall can hold up the room.
Check another area
Use Check My Wall for each area: ready areas can be planned while damp areas stay on hold.