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White Powder On Brickwork
A white, dusty or crystalline bloom has appeared on the face of the bricks, often on a new wall.
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What's happening?
Efflorescence is salt that has come out of the wall, not something that has landed on it. Water moves through the brick and mortar dissolving soluble salts as it goes, then evaporates at the surface and leaves the salt behind as a white bloom. It is extremely common on new brickwork, because fresh bricks and fresh mortar are still full of construction water, and it usually fades over the first year or two as that water dries out and the available salts are used up. The version worth attention is the one that keeps coming back on an older wall, because that means water is still moving through the masonry from somewhere and has not run out of salt to carry — which makes the bloom a symptom of a leak rather than a blemish.
What usually causes it?
- Construction water drying out of new brickwork and mortar, which is the normal and self-limiting case
- Bricks stacked unprotected on site and rain-soaked before they were laid
- A persistent water source — leaking gutter, cracked downpipe, failed cill, overflow — feeding the same area
- Missing or bridged damp proof course drawing ground salts up into the lower courses
- Cement-rich mortar or render releasing free lime, which shows as a harder white deposit
- Ground or paving raised against the wall so it stays wet and salt-laden
- A blocked or missing cavity tray letting water track across to the inner leaf and dry through the face
Is it dangerous?
The bloom itself is harmless — it will not weaken the wall and it is not toxic. What matters is what it tells you. Salt crystallising inside the brick rather than on its surface is one of the main causes of spalling, so persistent efflorescence on an older wall often precedes brick faces blowing off. A hard white deposit that will not brush off is usually lime leaching out of cement mortar, and that can stain permanently. And efflorescence appearing inside on a plastered wall, alongside a damp patch, points at water entering the structure and needs the leak found rather than the salt wiped away.
Can I fix it myself?
On new brickwork, yes — and mostly by waiting. Brush the bloom off dry with a stiff bristle brush, ideally on a dry day, and let the wall carry on drying. Do not wash it off with water, because that dissolves the salt and carries it back into the brick to reappear later. Avoid acid-based brick cleaners on a domestic wall unless you know the brick tolerates them; used wrongly they etch the fired face and leave a permanent patchy stain, and on some bricks they trigger fresh staining of their own. If it keeps returning after brushing, stop cleaning and start looking for the water.
When should you call a bricklayer?
Call a bricklayer if the bloom keeps returning on an older wall, if it is concentrated in one patch, if the deposit is hard rather than powdery, or if brick faces near it have begun to flake. Also call if it appears on the lower courses along with damp inside, which suggests the damp proof course is bridged or has been built over rather than that the wall is simply drying out.
What will the bricklayer actually do?
- Establish whether the wall is still drying from construction or is being wetted by an ongoing fault
- Trace the water path — gutters, downpipes, cills, cavity trays, ground levels — before cleaning anything
- Dry-brush and, where appropriate, correctly clean the affected brickwork without driving salt back in
- Repoint joints where a cement-rich mortar is leaching lime onto the brick faces
- Reinstate or unbridge the damp proof course, or lower ground levels, where salts are coming from the ground
- Replace bricks whose faces have already spalled from salt crystallisation inside them
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