Why has my new brickwork gone white?
Efflorescence brushes off and goes away on its own. Lime bloom does not, and needs completely different treatment. Telling them apart takes about ten seconds.
- Difficulty
- beginner
- Time
- 15 min
- Read
- 4 min
Short answer
Rub it with a dry finger. Fluffy white powder that brushes off easily is efflorescence — soluble salts brought out of the brick or mortar as the wall dries, harmless, and it stops once the wall has dried out. A hard white film that will not brush off is lime bloom, a carbonate deposit that needs a proprietary brick cleaner. Do not wash either one off with water.
New brickwork very commonly goes white in its first year, and it alarms people who have just paid for it. In the great majority of cases it is efflorescence, it is a symptom of the wall drying out rather than of anything being wrong, and it will disappear over the first couple of years without intervention. The important thing is not to make it worse, which washing it down reliably does.
Step by step
- Do the finger test first.Dry finger, firm rub. Powder that comes away is efflorescence. A film that stays is lime bloom. They look similar and they need opposite treatment.
- Work out where the water came from.New brickwork is full of water — from the bricks, from the mortar, and from rain during construction. That water leaves over the following months and brings salts with it. If the wall is otherwise sound, that is the whole explanation.
- Brush efflorescence off dry.A stiff bristle brush, on a dry day, brushing downwards and away. Collect what falls rather than letting it wash back down the wall.
- Never hose it off.Water dissolves the salts and carries them straight back into the brick, where they wait for the next drying cycle. Washing efflorescence off makes it recur worse and for longer.
- Be patient with it.It commonly appears through the first winter, reduces through the second and disappears. Nothing needs to be done except brushing.
- Treat lime bloom with a proper product.Proprietary brick cleaners for lime bloom are acid-based. Test on an inconspicuous area, dampen the brickwork first so the acid does not get drawn into dry brick, work in small sections, and rinse thoroughly. Some bricks are damaged by acid, which is why the test patch is not optional.
- Do not seal or paint a wall that is still efflorescing.A sealer or a paint over a wall that is still drying traps the salts behind the coating, where they crystallise and push the coating off. Wait until the whitening has stopped entirely.
- Escalate if it is still happening after two winters.Persistent efflorescence means ongoing water ingress. At that point it is a damp investigation, not a cleaning question.
Tips
- Efflorescence is one of the most common causes of a new-build complaint and one of the least serious. Builders and brick manufacturers both regard it as a normal part of drying out.
- It is more likely where bricks got soaked on site. Keeping brick packs covered and keeping the tops of unfinished walls covered overnight reduces it substantially.
- Acid brick cleaners are strongly corrosive and damage glass, aluminium, paintwork and plants. Mask everything nearby and wear the protection the label specifies.
If it doesn't work
White fluffy powder that brushes off with a dry brush
Cause: Efflorescence — soluble salts carried to the surface by water leaving the masonry, then left behind as the water evaporates — Fix: Brush it off dry with a stiff bristle brush, on a dry day, and repeat as it reappears. It reduces each time and stops entirely once the wall has finished drying out. Do not wash it.
A hard white or grey film that will not brush off, often in streaks
Cause: Lime bloom or lime run — calcium hydroxide leached out of fresh mortar, then converted by air to insoluble calcium carbonate on the face — Fix: This will not weather off quickly. Use a proprietary brick cleaner formulated for lime bloom, following the instructions exactly, with a test patch first. Dampen the brickwork before applying any acid-based cleaner.
White staining reappearing every winter, years later
Cause: The wall is still getting wet from somewhere — a leaking gutter, a bridged damp proof course, a failed joint, saturating render — Fix: Stop treating the symptom and find the water. Persistent efflorescence years after construction means water is still moving through the wall.
Whitening concentrated below a window, a sill or a coping
Cause: Water running off a detail and down the face, carrying salts with it — Fix: Look at whether the sill or coping has a drip, and whether it throws water clear. A detail without a drip runs water back onto the wall and produces exactly this pattern.
White deposits with the mortar joints also crumbling
Cause: Salt crystallisation happening within the joint rather than at the face, which is destructive rather than cosmetic — Fix: Find the moisture source. Persistent salt action in a joint means it stays wet, and the pointing will keep failing until that changes.
Whitening inside on a wall, damp to touch, worse in muggy weather
Cause: This is a different problem — hygroscopic salt contamination rather than construction efflorescence — Fix: Diagnose it as a damp problem rather than a masonry finish problem.