Short answer
Clean brick gently: brush off loose dirt, wet the wall, apply a masonry cleaner or biocide suitable for brick, scrub lightly with a stiff synthetic brush and rinse at low pressure. Avoid high-pressure jets and strong acid cleaners unless you know exactly what you are doing, because both can damage the brick face and the mortar joints.
Look at the wall first
Brick varies a lot. Hard, modern facing bricks cope with cleaning far better than older, softer bricks, which can lose their face easily. Look at the mortar too. If it is crumbling, missing or recessed deep into the joints, water and scrubbing will make it worse, and the wall may need repointing rather than cleaning.
Work out what the staining actually is. Green growth is usually algae, black streaks often run from sills and ledges, white powdery deposits are usually salts coming out of the masonry, and general grey grime builds up on walls near busy roads. Each needs a slightly different approach.
What you will need
A soft brush for loose dirt, a stiff synthetic scrubbing brush, a bucket, a garden hose or a garden sprayer, and a masonry cleaner or biocide suitable for brick. Avoid wire brushes, which scratch the brick and can leave metal fragments that later rust and stain. Wear gloves and eye protection, and protect plants and paving below the wall.
How to clean brick walls, step by step
- Brush the wall down with a soft brush to remove cobwebs, loose dirt and dry debris.
- Choose a dry, overcast day and soak nearby plants with plain water.
- Test your chosen cleaner on a small, hidden area of brick and let it dry before judging the result.
- Wet the brickwork with clean water so the product does not soak straight in.
- Apply the cleaner or biocide following the label, working from the bottom upwards to avoid streaks. Never mix products.
- Leave it for the contact time given, then scrub lightly with the synthetic brush, without digging into the mortar joints.
- Rinse gently with a hose, working from the top down, until the water runs clear.
White deposits on brick
White, powdery marks on brickwork are usually salts carried to the surface as water evaporates from the wall, a process known as efflorescence. It is common on new walls and after wet spells. Brush it off when the wall is dry rather than washing it, because adding water can draw more salts out.
If it keeps returning in one area, it suggests water is getting into the wall there, perhaps from a leaking gutter or downpipe, so it is worth finding and fixing the source.
Why to avoid high pressure and strong acids
A high-pressure jet can scour the surface of brick, especially older brick, and wash out mortar from the joints, leaving the wall more open to water and frost. Once the hard outer face of a brick is damaged, it tends to weather faster and hold more dirt.
Strong acid-based brick cleaners are sometimes used by builders to remove mortar smears on new walls, but they can etch the brick, discolour it and harm plants. They are not suitable for routine cleaning, and should only be used by someone experienced with them, following the safety guidance closely.
Paint, graffiti and stubborn staining from metalwork need specific treatments; general cleaning products rarely remove them and can spread the mark.
Garden walls and features
Garden walls, pillars and brick planters often stay damp and shaded, so they turn green quickly. The same gentle method works. Clear soil and leaves from the base of the wall, trim back plants growing against it so it can dry, and check that copings and caps are sound so water is not running into the brickwork from the top.
When to call a professional
Call a professional for anything above ground-floor height, for whole elevations, for older or soft brick, or where earlier cleaning has left the wall patchy. A professional can also tell you whether the wall needs repointing or repair before any cleaning is done.
We clean brick and stone walls by soft washing, a low-pressure method with a specialist solution that kills algae at the root and protects the mortar joints. We look at the material, mortar and staining before suggesting an approach, and include biocide treatment where growth tends to return. Our guide to soft washing vs pressure washing explains the difference in methods.
Rather have it done for you?
Soft washing of brick and stone walls to lift algae, staining and grime. Family-run by Jason and Lucas Prior, covering south Essex.
Frequently asked questions
Can you pressure wash brick?
It is risky. High pressure can damage the brick face and wash out mortar, particularly on older walls. A low-pressure clean with a suitable masonry cleaner or biocide is the safer option.
What is the white stuff on my brick wall?
Usually salts brought to the surface as water dries out of the wall. Brush it off when dry, and if it keeps coming back in one spot, look for a source of water such as a leaking gutter.
Can I use bleach on brick?
Bleach can discolour brick and harm nearby plants, and it should never be mixed with other products. A cleaner or biocide made for masonry is the better choice; test it on a hidden area first.
Related guides
- Soft washing vs pressure washing: what soft washing is, how it differs from pressure washing and which outdoor surfaces suit each method.