Question: What are the white powdery patches growing on my wall?
Answer: That is efflorescence — mineral salts dissolved out of bricks, mortar or concrete by moisture moving through the wall. When the water reaches the surface and evaporates, it leaves the salts behind as a white, powdery or crusty deposit. Efflorescence itself is cosmetic, but it is a reliable witness: it proves water is travelling through the wall from somewhere. Scraping it off without stopping that moisture path means it returns, usually with bubbling paint and mould joining in.
This article covers the wall dampness & efflorescence repair sub-service under waterproofing services, starting from RM 350. Related scopes: PU high-pressure injection grouting for leak paths in concrete, and wall crack & moisture repair once the wall is dry and ready for refinishing. Problem guides: rising damp on walls and damp walls and paint bubbling. Not sure what kind of damp you have? The leak triage tool helps narrow it down.
Efflorescence vs Three Kinds of Damp
The same white salt and bubbling can come from very different sources, and the repair differs for each:
| Source | Typical pattern | Where it shows | Core fix |
|---|---|---|---|
| Rising damp | Horizontal band from floor level, salt line at the top edge | Ground-floor walls, boundary walls | Block the moisture path from the ground; treat the wall |
| Leak-driven damp | Localised patch growing around a stain | Near bathrooms, pipes, roof edges | Repair the leak first, then restore the wall |
| Condensation | Surface moisture, mould in corners and behind furniture | Air-conditioned rooms, shaded walls | Ventilation, insulation, anti-condensation measures |
A professional inspection with moisture readings tells these apart — that diagnosis is the most valuable part of the job, because the wrong treatment wastes money no matter how well it is applied.
What the Repair Includes
The published scope starts at RM 350 and, once the moisture source is fixed, typically follows this sequence:
- Source confirmation — moisture readings mapped across the wall to confirm where water is entering and whether it has stopped.
- Salt removal — the affected paint, salt crust and loose plaster are scraped and sanded back to a sound surface.
- Mould sanitising — visible mould growth is treated so spores are not sealed under new coatings.
- Drying — the wall needs actual drying time; trapping residual moisture under a new coating recreates the problem.
- Moisture-blocking barrier — a commercial-grade moisture sealer blocks remaining salt migration and locks the surface.
- Refinishing — skim, prime and repaint, usually as part of the related painting scope.
When Surface Repair Is Not Enough
- Rising damp on ground-floor walls often needs a treatment at the source side — a damp-proof course injection or an external moisture barrier, not just internal sealing.
- Leaks from an adjoining unit or a bathroom above must be fixed at their source first — see bathroom & wet area waterproofing.
- Active water paths through concrete can be stopped with PU injection grouting where cracks or joints are the entry route.
- External walls facing driving rain may need a breathable exterior water-repellent rather than an internal barrier alone.
The waterproofing service carries a published Up to 5-Year Written Leak-Free Guarantee within its terms.
Cost Factors
The wall dampness & efflorescence repair sub-service starts from RM 350; waterproofing services start at RM 300 overall. Final cost depends on:
- Number and size of affected walls.
- Whether the moisture source has already been resolved or needs its own repair scope.
- Extent of plaster removal and mould treatment.
- The barrier system needed — internal sealer vs source-side treatment.
- Drying time and follow-up visits before refinishing.
- Skimming and repainting scope after treatment.
Common Mistakes to Avoid
- Scraping the white deposit off and repainting the same week — the moisture is still inside.
- Sealing over a wall that is still damp at its core.
- Painting anti-mould paint over an untreated moisture source.
- Ignoring the same patch after it dries in the hot season — it returns with the monsoon.
- Assuming every white patch is condensation; rising damp and leaks both leave salts too.
Frequently Asked Questions
Is efflorescence harmful to health?
The salt deposits themselves are mineral and not toxic, but they signal constant moisture — and moisture is what feeds mould growth, which does affect indoor air. Treat the moisture, not just the deposit.
Why does the white patch keep coming back after I brush it away?
Brushing removes surface salt but the moisture path inside the wall is still delivering more salts to the surface. Until the water entry and the internal salt reservoir are both addressed, the deposits reform — often within weeks after the next rain.
How long must the wall dry before repainting?
It depends on wall thickness and how saturated it was. A wall that held moisture for months may need weeks of drying, sometimes assisted with dehumidification, before a moisture barrier and paint can be applied without trapping damp inside.
Dry the Wall, Then Finish It
Efflorescence is your wall reporting a moisture problem — listen to it. KL Servis Rumah diagnoses and treats damp walls and salt deposits across Kuala Lumpur and Selangor.
Send photos of the affected wall at its widest and the salt patches up close — WhatsApp the waterproofing team.