Short answer: yes, you can pressure wash an exposed aggregate driveway, just not the way you'd blast plain concrete. Use a wide fan tip or a rotary surface cleaner, keep the nozzle back, treat stains before you spray, and never chase a mark with a narrow jet. The stones are held by the cement paste around them, and that paste is what a heavy-handed clean strips away.
We're a family-owned Byford team, and exposed aggregate is everywhere in the estates we work in. Here's what's safe to do yourself, which Perth stains need treating first, and when it's worth booking professional driveway pressure cleaning.
Why exposed aggregate can't be cleaned like plain concrete
Exposed aggregate is concrete with the top film of cement washed off as it sets, leaving the decorative stones showing. It's tough, grippy and hides everyday dirt, which is why it's on so many driveways and alfresco slabs in newer estates in Byford, Piara Waters and Harrisdale.
The catch is that each stone is only partly buried, gripped by cement paste. On plain concrete, a little surface erosion just looks rougher. On aggregate, eroding that paste loosens the stones, and once they pop out you need a repair, not a clean. Many aggregate driveways are also sealed. The sealer gives that "wet look" colour, but too much pressure or the wrong chemical can scar, cloud or strip it.
Can you pressure wash exposed aggregate?
Yes, and done properly it's the most effective way to lift built-up dirt and growth. Four things matter:
- Nozzle. Use a wide fan tip or, better, a rotary surface cleaner for an even, stripe-free result. Keep zero-degree (pencil) and turbo nozzles off the driveway; they focus the force on a tiny spot.
- Distance. Start well back and only move closer if the dirt isn't shifting. If cement is washing out between the stones or grit shows up in the runoff, back off.
- Angle. Hold the wand on an angle rather than straight down, keep it moving, and work with the fall of the driveway.
- Pressure. More isn't better. Start low and test a hidden spot first, such as beside the bins.
A household or hire machine can handle a lightly soiled driveway if you go gently. Wear eye protection and enclosed shoes, and keep kids and pets clear. Safe Work Australia lists the water jet piercing skin and flying debris among the common hazards of high-pressure water jetting, so never point the wand at anyone.
Common Perth stains on exposed aggregate
- Sand and soil from new landscaping and retic overspray, especially along garden edges. A sweep and a fan-tip rinse usually shift it.
- Tyre marks where the car turns or parks. Surface grime lifts with a degreaser, but marks that have softened into the sealer may only lighten.
- Oil drips under where the car sits and in carports.
- Orange speckles and arcs from fertiliser, sulphate of iron or bore water.
- Mould, algae and moss on shaded side paths and along south-facing walls after a wet winter.
Our rule is treat first, blast second. Pressure removes loose dirt and organic growth, but it doesn't dissolve oil or iron, and turning it up to compensate is how stones get loosened.
How to get oil stains out of exposed aggregate
- Catch it fresh. Cover a new spill with cat litter or sawdust, let it soak, then sweep it up and bag it. Don't hose it: water just spreads the oil towards the street drain.
- Choose a concrete degreaser whose label says it suits exposed aggregate or sealed surfaces, and test a small patch. Wear rubber gloves and eye protection.
- Give it time. Work it in with a stiff nylon brush (a wire brush can scratch the sealer and leave rust spots) and leave it for the dwell time on the label. In summer, do it early while the slab is cool, so the product doesn't dry before it has had time to work.
- Rinse with a wide fan, steering the runoff away from the street drain, let it dry, and check the result before trying a second round.
A pressure washer alone tends to spread oil rather than lift it. Be realistic about old stains, too: oil that has sat for months often gets beneath the sealer, so even our hot water equipment and a commercial degreaser may only lighten it. We'll tell you honestly what to expect before we start.
Orange marks: fertiliser, sulphate of iron or bore water?
Orange-brown marks are usually iron, and the pattern tells you the source:
- Small round speckles near lawn and garden edges are typically fertiliser or sulphate of iron granules that landed on the driveway and got wet.
- Arcs and stripes that match your sprinkler spray point to bore water. Our guide to bore water stains in Perth covers those.
Pressure won't shift iron, so treat first with a rust or iron stain remover. Some are acid-based and can etch the concrete, so use only a product labelled for exposed aggregate and follow its dilution and dwell time exactly. Test a hidden patch first, wear gloves and eye protection, and never use it on the same area as bleach or another cleaner. To prevent new marks, sweep stray granules back onto the lawn before watering and adjust any sprinklers that hit the driveway.
Acid, bleach and exposed aggregate cleaners: what to watch out for
Plenty of online advice suggests hydrochloric (muriatic) acid or bleach. We don't recommend either for a DIY driveway clean.
- Hydrochloric acid attacks the cement paste holding the stones, and can etch the surface and leave it patchy. Safe Work Australia lists hydrochloric acid among corrosives, which damage skin and eyes and can burn the throat and airways if the fumes are inhaled.
- Bleach is often suggested for mould, but you don't want it running into lawns, garden beds or the street drain.
- Never mix them. Household bleach is sodium hypochlorite, the same chemical as liquid pool chlorine, and Safe Work Australia warns that pool chlorine releases poisonous chlorine gas on contact with acid.
Off-the-shelf exposed aggregate cleaners range from acid-based to detergent or alkaline formulas, so check the label before you buy. HealthyWA advises reading the instructions every time you use a product, wearing rubber gloves and eye goggles, and not mixing products unless the label says to. Test a small patch first, and if you suspect poisoning, call the Poisons Information Centre on 13 11 26 (24 hours a day).
Think about the runoff too. Water Corporation notes that stormwater washes sediment, grease and oil from roads and properties into our waterways, so use the least chemical that does the job and sweep up residue rather than hosing it into the street.
Cleaning before resealing
If the sealer is patchy, cloudy or worn through in the wheel tracks, resealing brings the colour back. Sealing is a separate trade, and it isn't something we offer.
What we can do is the clean beforehand. Sealer locks in whatever is on the surface, so dirt, oil, mould and chemical residue need to be gone, and the slab usually needs to be dry before it goes on. If the old sealer is failing, stripping is your sealing contractor's call. Ask what preparation and drying time they need, and we'll book the clean to suit.
How often should you clean an exposed aggregate driveway?
There's no set schedule. A proper clean makes sense:
- Before summer entertaining, ideally in spring before the alfresco gets busy.
- After winter on shaded areas, where algae and moss build up over the wet months.
- Before a sale or rental handover, because it's the first thing buyers and property managers see.
If you're renting, Consumer Protection WA says tenants are expected to leave the home in a similar condition to when they moved in, allowing for fair wear and tear. Oil drips that weren't there at the start are worth tackling before the final inspection. We pressure clean driveways and outdoor areas as part of our specialist end of lease cleaning, and our final inspection checklist covers the rest.
Should you DIY or call a professional?
A lightly dirty driveway with no real stains is a fair DIY job if you take it slowly. It's worth calling us when:
- there are old oil, iron or tyre marks that need treating first
- it's a big area, such as a long driveway plus pool paving and limestone paths
- the sealer is tired or some stones are already loose
- it's a commercial forecourt, like those in the Canning Vale industrial area
We use commercial-grade hot and cold water equipment, with the pressure and nozzle set for aggregate, pavers or limestone. If we spot loose or crumbling patches, we'll tell you before we start. See the outdoor surfaces we clean, or request a free quote.