Damp and seepage
What the white powder on your walls is telling you.
That chalky white deposit that keeps coming back on a wall is called efflorescence. It's the salt left behind after water has moved through the wall, so it's less a stain than a message about moisture.
Reviewed 21 September 2026 by PremiumWalls operations.
At a glance
What is the white powder on my walls and how do I get rid of it?
It's efflorescence, salts carried to the surface by moisture moving through the wall and left behind as the water dries. Brushing it off removes the deposit but not the cause. It returns until the moisture source is found and stopped, so treatment starts with finding where the water is coming from and only then repairing and repainting.
White Powder on Walls: What Efflorescence Means
What efflorescence actually is
Bricks, blocks, cement and plaster all contain small amounts of soluble salts. When water passes through the wall it dissolves some of them and carries them to the surface. The water evaporates and the salts stay behind as a white, powdery or sometimes crystalline crust.
What it says about moisture
No moisture, no efflorescence. If it appears, water is moving through that part of the wall, whether that's from the ground, a leaking terrace or pipe, a damp exterior face or a wet bathroom on the other side. On a brand new building it can also be residual moisture drying out of fresh plaster, which is why a new apartment can show it in the first monsoon after handover.
Why brushing it off is not a repair
A dry brush or wipe takes the powder away and the wall looks clean for a while. The salts are still in the wall and the moisture is still travelling through it, so the deposit reforms. If you see it come back in the same place, that's useful information about where the water is moving.
Why repainting over it fails
Salts that crystallise behind a paint film push it away from the wall, and the paint blisters, flakes and peels in patches. Fresh paint over an untreated wall often looks worse than the powder did, because the damage is now uneven and coloured. The paint has to bond to a clean, sound, dry surface, and a salt-laden wall isn't one.
What proper treatment involves
In general terms, the order matters. First the moisture source is found and dealt with. Then the affected paint and any loose or salt-damaged plaster are removed, the surface is cleaned of deposits and left to dry fully, and repairs are made. Only after that goes on the primer and paint appropriate to the wall, chosen after inspection.
Walls that have it, and where to look
Look for it near the base of ground-floor walls, under windows, around bathrooms and kitchens, below terrace parapets and on outer walls that get rain. A repeating pattern usually points at one shared cause, such as a gutter or outlet that's spilling onto the wall, so it's worth noting where it shows before anyone starts work.
White Powder on Walls: What Efflorescence Means — your questions.
Is efflorescence harmful to health?
The salt deposit itself is generally a nuisance rather than a hazard, though you shouldn't sweep it into the air and breathe it in. What matters more is the moisture behind it, which can lead to peeling paint, weakened plaster and mould.
Can I wash it off with water?
Wetting the wall adds moisture and dissolves the salts, which can pull more of them to the surface as it dries. It's better to brush the loose powder off dry and get the cause looked at than to keep washing the wall.
Does new plaster get efflorescence?
It can, as new plaster and masonry release moisture and salts while they dry. That's one reason we advise waiting for a new wall to be fully dry before painting, and checking it rather than judging by how it looks.
How do I know if it's a leak or just old salts?
If the powder returns after you've brushed it away, or the wall feels cool or damp near it, water is still on the move. An inspection can tell you where from. We offer a free colour and wall inspection with a written itemised quotation.
Let us look at your walls first.
Tell us about the property and we will set up a free colour and wall inspection. You get a written, itemised quotation afterwards, with no obligation to go ahead.
- We call you back the same day to get a picture of the property and the surfaces.
- We agree a time and come out for the free inspection.
- You get the written scope and itemised quotation.
- Nothing starts until you approve it.