Brick is fired clay and it is nearly indestructible; the mortar between it is not. Most brickwork damage comes from cleaning that was too aggressive for the joint — too much pressure, too much acid, or a wire brush where a soft one would have done.
Low pressure, right chemistry, soft tools
Clean brick with a stiff nylon brush and an alkaline cleaner for general soiling, using a pressure washer at low pressure and at an angle rather than square-on. Acid is for efflorescence only, and a mortar joint that has already eroded should be cleaned by hand rather than blasted.
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Match the method to the soiling
| Soiling | Method | Caution |
|---|---|---|
| Dust, pollution film, cobwebs | Stiff nylon brush and a hose, or low-pressure wash | Do not point the jet into the mortar |
| Moss and algae | Scrape, wash, then a residual treatment | Cleaning alone does not stop regrowth |
| Efflorescence (white salt bloom) | Dry-brush first, then a mild acid wash and rinse | It returns if water is still migrating through the wall |
| Graffiti | Masonry-specific graffiti remover, poultice style | General solvent pushes paint deeper into porous brick |
| Oil and grease | Alkaline degreaser with dwell time, then a low-pressure rinse | Do not scrub it in |
The pressure washing rules
- Low pressure. A rotary nozzle held close to brick will erode the face and the joint. Use a wide fan nozzle and keep the wand moving.
- Angle the jet down and along the wall rather than square-on, so water is not driven into the brick.
- Work in sections and rinse as you go. Letting dirty water dry on brick leaves a film that is harder to remove than the original soil.
- Never blast a damaged joint. Where mortar has eroded, cleaning by hand is the only option that does not make the repair bigger.
Efflorescence and the water behind it
White bloom on brick is salt carried to the surface by water moving through the wall. Cleaning it removes the symptom; the cause is usually a leaking gutter, a cracked flashing, a sprinkler hitting the wall, or a garden bed holding moisture against the base course. Fix the water and the bloom stops returning.
Does vinegar damage brickwork?
Diluted vinegar does not damage fired brick, and it is a weak acid that will lift light mineral bloom. What it will do is attack lime mortar over repeated applications, and lime mortar is what older brickwork uses. On a heritage wall, use a pH-neutral product and a brush rather than arriving with acid.
Making brick look new
Cleaning restores the colour that is under the film, and it does not change the brick. Where a wall looks permanently tired after cleaning, the causes are usually paint or render that has failed, a mortar that has been repointed in a different colour, or a factory finish that has weathered differently across the wall. Those are masonry repairs rather than cleaning jobs.
New brickwork and aged brickwork are different jobs
New brick has mortar that is still curing, and water used too early can wash out the lime and leave a chalky, friable joint. On anything built in the last month, clean with a soft brush and no pressure until the mortar has cured, and use a builder’s clean product rather than an acid wash.
Aged brick is the opposite problem: the face has been weathered and the joints may already have eroded, so aggressive cleaning takes the last of the surface with it. On a wall more than fifty years old, expect to clean by hand and to accept a slightly mottled result — a uniform finish on old brick usually means something was sandblasted or coated, and both are repairs dressed up as cleaning.
Painted brick, render and coated masonry
Once brick has been painted, the rules change. The paint film is the surface, and aggressive cleaning takes the paint with the dirt: pressure washing lifts it at the edges and along the joints, and a masonry solvent remover softens it. On painted brick, clean with a soft brush and a mild detergent, work in small sections, and rinse before the solution dries.
Render and textured coatings behave the same way. A render that has been painted with an elastomeric coating will tolerate a low-pressure wash and a soft brush; one painted with a standard acrylic will not tolerate much at all. Where a wall needs a full removal, that is a paint-stripping job with the surface prepared for recoating, not a cleaning job dressed up as one.
Questions we get asked most
- What is the best thing to clean bricks with?
- A stiff nylon brush with an alkaline cleaner for general soiling, and a masonry-specific remover for paint and graffiti. Acid is reserved for efflorescence.
- How do you make brick look new?
- Remove the film rather than the surface: brush, clean with the right chemistry, and rinse. Aggressive pressure washing removes the brick face and leaves it lighter but rougher.
- Can I pressure wash brickwork?
- Yes, at low pressure with a wide fan nozzle, angled down the wall. Keep the jet out of the mortar joints, and hand-clean any joints that are already eroded.
- Does vinegar damage brickwork?
- Not fired brick. It does attack lime mortar over time, which matters on older and heritage walls — use a neutral cleaner there.
- What removes white bloom from brick?
- Dry-brush it first, then a mild acid wash with a thorough rinse. If it returns, find the water getting into the wall — bloom is a drainage problem showing up on the surface.
References
- SafeWork NSW — machinery and equipment.
- NSW Environment Protection Authority — chemicals and wash water.
Brickwork across a site?
Send a photo and tell us whether it is painted, rendered or bare, and we will match the method and the pressure so the joints survive it. Browse cleaning chemicals or ask our team.