The quickest way to clean paving in Cape Town is a stiff broom, a bucket of warm water with a little dishwashing liquid, and a proprietary moss and algae treatment left to work for a week. That handles the green film and black marks on most driveways and patios. What you should be far more careful about is the two things people reach for first — a high-pressure washer on full power, and acid.
Both of them clean beautifully on day one and cause damage you will still be dealing with in three years. Here is what actually works on each type of staining, in the order we would try it, and what to leave alone.
Why Cape Town paving goes green
Moss and algae are a winter-rainfall problem, and Cape Town has the only major winter-rainfall climate in South Africa. From roughly May to August, cold fronts keep surfaces damp for weeks at a time, days are short, and the sun is low. Any paved area that stays wet and shaded grows a green film. By August a north-facing driveway may be spotless while the south side of the same house is slippery.
The predictable trouble spots:
- South-facing paving that gets almost no winter sun.
- Under trees and eaves, where drips keep one strip permanently damp.
- Low spots that hold water — usually a drainage or falls problem wearing a cleaning disguise.
- Pool surrounds, which are wet all summer as well.
- Shaded Southern Suburbs gardens in Newlands, Bishopscourt and Constantia, where damp and leaf litter combine.
The black marks are slightly different. Lichen appears as small dark crusty spots that grip hard, and general black staining is usually a mix of dead algae, road grime and organic residue. Both respond to the same treatments, lichen just takes longer.
The method that works, step by step
- Clear the surface. Sweep off leaves and debris. Pull weeds from the joints by hand or with a joint knife — roots left in place regrow within weeks.
- Sweep hard, dry. A stiff yard broom removes a surprising amount of loose algae before any water is involved.
- Wash with warm soapy water. Warm water and a squirt of dishwashing liquid, scrubbed with the broom, then rinsed with a hose. On light green film this is often all it takes.
- Treat what remains. Apply a moss and algae killer sold for paved surfaces, following the dilution on the bottle. Apply on a dry, still day — the south-easter will put it in your beds otherwise. Leave it. Most products need days to a couple of weeks to fully kill the growth.
- Sweep off the dead residue and rinse.
- Re-sand the joints. Non-negotiable, and the step everyone skips. Brush dry kiln-dried sand into all the joints until they are full, then sweep off the excess. The joint sand is what makes interlocking paving work — without it the bricks lose their interlock and start to move.
What to use on specific stains
| Stain | What works | Avoid |
|---|---|---|
| Green algae film | Warm soapy water and a stiff broom; algae treatment if stubborn | Acid |
| Moss in joints | Joint knife, then moss killer, then re-sand | Pressure washer aimed into joints |
| Lichen spots | Repeat applications of algae treatment, patience | Scraping with a steel blade |
| Oil and engine drips | Absorbent granules or cat litter first, then a degreaser | Petrol or thinners |
| Leaf and tannin staining | Oxygen-based cleaner, several passes | Bleach on coloured pavers |
| Rust from furniture or irrigation | A rust remover made for masonry, spot-applied | Hydrochloric acid |
| Efflorescence (white bloom) | Usually nothing — it weathers off over months | Acid washing to “fix” it |
Why acid is a bad idea
Hydrochloric acid, sold as spirits of salts, is widely recommended in South African hardware shops for cleaning paving. It works — because it dissolves the cement paste on the surface of concrete pavers. That is not cleaning, it is etching. You end up with a surface that is rougher, more porous, faded in colour, and considerably more attractive to the next generation of algae than it was before. On clay pavers it can bleach the colour unevenly, and it corrodes any metal edging, gate track or drain grating it runs into. It also kills whatever it reaches in your beds and is genuinely hazardous to handle.
If a contractor’s cleaning quote includes an acid wash, ask what for. The only legitimate use is removing cement smears left after installation, and even then it is a careful, diluted, spot application — not a general clean.
Pressure washing: useful, frequently misused
A pressure washer is a legitimate tool, and we use one. The damage comes from how most people run it: maximum pressure, a narrow pencil jet, held close and pointed at the joints.
That blasts the jointing sand straight out. Once the joints are empty, the bricks lose lateral support, the surface starts to move under traffic, and water begins running into the base rather than across the surface. Every winter after that makes it worse. A high-pressure jet can also erode the face of the paver itself, leaving a permanently rougher, dirt-trapping surface.
If you are going to use one:
- Use a fan nozzle, not a pencil jet or turbo head.
- Keep the lance at least 300mm off the surface.
- Work at a shallow angle, sweeping across the joints rather than down into them.
- Use the lowest pressure that does the job.
- Always re-sand afterwards. Always. If you are not prepared to re-sand, do not pressure wash.
- Never pressure wash artificial lawn or its edges.
Household remedies: which ones are worth it
Bleach kills algae effectively but can lighten coloured pavers unevenly and will damage nearby planting. If you use it, dilute heavily, test in a hidden corner, wet the surrounding beds first and rinse thoroughly.
White vinegar is mild and safe on plants but it is still an acid, just a weak one, and it is not particularly effective on established lichen. Fine for a light green film on a small patio.
Salt — do not. It kills the moss and then hangs around damaging planting and, in coastal suburbs like Blouberg and Table View, adds to a salt load the surface is already carrying from the sea air.
Boiling water works surprisingly well on weeds in joints and costs nothing.
Stop it coming back
Cleaning treats the symptom. If your paving goes green every single winter in the same place, something structural is causing it.
- Sort the drainage. Paving that holds water after rain has inadequate falls or nowhere to drain to. That is the actual problem — our driveway drainage guide covers the options, from channel drains at R1 200–R2 800 per running metre installed to full redesigns.
- Cut back overhanging growth. Getting winter sun and airflow onto a surface does more than any chemical.
- Keep the joints full. Full joints shed water. Empty joints hold it and grow things.
- Clear leaf litter through autumn. Wet leaves left on paving through May feed the algae that appears in July.
- Consider sealing — but only on suitable materials and only on a properly dry, clean surface. It runs roughly R45–R85 per m² in premium materials and it is not a cure-all. Sealed paving still grows algae if it stays wet.
Timing and budget
The best time to clean is late summer to early autumn, February through April. The surface is properly dry, treatments work better and last longer, and you go into winter with full joints and a clean surface rather than trying to scrub a wet driveway in July.
For a typical home with 80–120m² of paving, doing it yourself — sand, moss killer, a hired pressure washer — runs about R600–R1 200. A professional annual service that cleans, re-sands, treats moss and inspects the surface sits around R2 500–R5 500. Our paving maintenance guide sets out the full annual routine.
If cleaning reveals that the real issue is movement, sunken sections or standing water rather than dirt, that is a base and drainage problem and no amount of scrubbing will touch it. Have a look at our driveway paving service for what a proper rebuild involves, or send us a few photos and we will tell you straight whether you need a clean or something more.
Quick answers
What is the best way to clean paving in South Africa?
Sweep the surface, wash with warm soapy water and a stiff broom, then apply a moss and algae treatment and leave it to work for a week or two. Sweep off the dead residue and re-sand the joints with kiln-dried sand. That handles the vast majority of green film and black marks.
Can I use acid to clean paving?
We would not. Hydrochloric acid dissolves the cement paste on concrete pavers, leaving them rougher, more porous and faded — which makes future algae growth worse, not better. It also bleaches clay pavers unevenly, corrodes metal fittings and damages nearby planting.
Does pressure washing damage paving?
It can. High pressure aimed into the joints blasts out the jointing sand that gives interlocking paving its strength, and it can erode the paver face. Use a fan nozzle at least 300mm off the surface, sweep at a shallow angle, use the lowest effective pressure, and always re-sand afterwards.