How do you remove efflorescence from concrete or brick?
A white film or white streaks on a brick wall, a low wall or a concrete slab? It is often efflorescence, common in spring in Quebec. It is mostly cosmetic, but it signals water infiltration.
Updated
Quick answer
Efflorescence is a deposit of white salts left by water passing through concrete or brick. To remove it, first brush it dry in dry weather; then, if it persists, apply an efflorescence cleaner diluted according to the manufacturer and rinse. To keep it from coming back, the source of moisture has to be fixed.
Time: 1 to 2 hours
What you need
- Stiff nylon-bristle brush (no wire brush)
- Efflorescence cleaner (a product made for masonry)
- Sprayer, clean water
- Gloves and safety glasses
Steps
- 1
Wait for dry weather
Work on a dry surface: wetting efflorescence dissolves the salts again, and they soak back into the material.
- 2
Brush dry
Brush the white deposits vigorously and sweep up the powder. This is often enough.
- 3
Apply a cleaner if needed
If marks remain, wet lightly, apply the efflorescence cleaner diluted according to the manufacturer, and let it work for a few minutes.
- 4
Rinse
Rinse thoroughly with clean water to neutralize the product.
- 5
Treat the cause
Check gutters, flashing, cracked joints and ground slopes: as long as water gets in, efflorescence comes back.
When should you call a professional?
If efflorescence comes back despite cleaning or covers a large facade, a professional can remove it and tell you where the water is coming from. HygiePro cleans the facades, low walls and concrete slabs of businesses across Greater Montreal.
Frequently asked questions
What causes efflorescence?
Water passing through concrete or brick dissolves the mineral salts they contain, then evaporates at the surface and leaves those salts behind as a white deposit.
Does vinegar remove efflorescence?
It can dissolve light deposits, but it is an acid that also attacks the surface of concrete and mortar. A cleaner made for efflorescence, tested on a hidden spot, is safer.
Should you pressure wash efflorescence?
No: pressurized water drives the salts deeper and the efflorescence reappears. Brush it dry first.