What can be water blasted?
Hard, well-bonded surfaces handle a water blaster best. That means plain broom-finished concrete, exposed aggregate, concrete pavers, clay brick paving and concrete block retaining walls. Each needs a different nozzle, pressure and distance, so the crew walks the site first and tests a hidden corner. Anything soft, painted, cracked or loose gets a gentler method or is left alone.
Most of what we quote on the North Shore is concrete: driveways, front paths, the strip down the side of the house and the patio out the back. For flat areas the crew uses a surface cleaner, a round hood with jets spinning underneath it. It cleans evenly and holds the spray close to the ground, which keeps splash off your cladding and windows.
- Plain concrete: the easiest surface. Moss, algae and grime lift cleanly, and the result looks even when the work is done in overlapping passes.
- Exposed aggregate: cleans well, but the stones sit in a thin layer of cement. Held too close or too long, a jet can loosen them, so the pressure comes down and the surface cleaner does most of the work.
- Pavers and brick paving: the faces clean up well, but the jointing sand between them washes out. Expect the joints to need refilling afterwards.
- Brick and block walls: sound walls with good mortar are fine at moderate pressure. Crumbly old mortar is not, and we will tell you if a wall falls into that group.
Timber decks are a different job again. High pressure lifts the soft fibres in the boards, so the crew cleans them with low pressure and a scrub. See our deck washing service for how that works.
What shouldn't be water blasted?
Never water blast a roof or cladding that could contain asbestos. WorkSafe says high-pressure water spraying, including water blasting, must not be used on asbestos-containing material, and the Asbestos Regulations specifically prohibit it. Buildings from before the 2000s, and decramastic roof tiles laid before asbestos was phased out, may contain it. Painted weatherboards, soft timber and crumbling mortar should not be blasted either.
WorkSafe's safety alert on high-pressure spraying of roofs describes a 1970s house with decramastic tiles that was water blasted. Debris ended up across the property and inside the home, testing confirmed asbestos in the tiles, and the place needed specialist remediation. Plenty of North Shore homes were built in that era, so this is not a remote risk.
If your roof or cladding is older than the 2000s, or you have decramastic tiles, check before anyone puts a machine on it. Any roof job we quote goes to a low-pressure soft wash, never a water blaster. Our soft washing service explains the method. If asbestos turns up partway through a job, the work stops and a specialist is called in.
The other surfaces we keep away from high pressure:
- Painted weatherboards and fascias: a jet strips sound paint and drives water behind the boards. Paint on older houses may also contain lead. Health New Zealand's lead paint guidance notes that many paints sold here before 1965 had high lead levels and that you can't tell by looking. House walls get a soft wash instead.
- Soft timber: pine decks, fences and pergolas furr up and splinter under high pressure.
- Old or soft mortar and render: the jet can cut into joints and leave a wall needing repointing.
- Cars, windows and seals: they get covered or masked, and the crew works away from them.
How do you get concrete clean again?
Concrete comes clean in two stages. A treatment goes on first to kill moss, algae and lichen down to the root, then the surface cleaner lifts the dead growth and grime in even passes. Blasting alone removes what you can see but leaves the roots in the pores, so green and black spots come back sooner. Old oil and rust stains often fade rather than disappear.
One New Zealand concrete products maker puts it plainly in its technical notes: water blasting removes moss, algae and lichen but won't stop them coming back, and it can damage the surface. That matches what we see on shaded North Shore driveways, where a blasted-only drive turns green again within a season or two.
What the crew does with each problem:
- Moss and algae: a moss and mould treatment first, given time to work, then the surface cleaner.
- Lichen and black spots: the small grey-white crusts and black dots are lichen. They grip hard, so they need the treatment to soften them before blasting. Lichen that has been there for years can leave a faint mark in the concrete even after it is gone.
- Oil stains: fresh oil responds to a degreaser or a biological oil remover. Old oil that has soaked deep into the slab usually lightens rather than vanishes, and we will say so at the quote.
- Rust and tannin marks: these need a spot stain remover made for the job. Pressure alone won't shift them.
We are honest about the limits. Concrete is porous, and a 20-year-old driveway will look much cleaner, not new. For a closer look at the DIY side, read our guide on how to clean a concrete driveway.
Should you seal concrete or pavers after cleaning?
Sealing is optional, but it is the best time to do it. A freshly cleaned, fully dry surface takes a sealer evenly, and a sealer slows down how fast moss, oil and dirt soak back in. Pavers usually need their joints refilled with jointing sand first. The surface must dry completely before sealing, and the product label sets the waiting time.
Concrete sealers fall into two broad types. Penetrating sealers soak into the pores and block water and stains from inside, leaving the surface looking much as it did. Film-forming sealers sit on top as a thin coat, often giving a slight sheen or a deeper colour. Some products combine both.
- Penetrating sealer: natural look, little change to grip underfoot, a good fit for driveways and sloping paths.
- Film-forming sealer: richer colour on exposed aggregate and coloured concrete, but it wears in tyre tracks and can get slippery when wet unless it has a grip additive.
Ask about sealing when you ask for a quote and we will price it as a separate line, so you can decide either way.
Where does the run-off go?
Not into the stormwater drains. Auckland Council's guidance on pressure washing says wash water carries grime, algae, moss, sediment and grease, and that even biodegradable detergents are not permitted to enter the stormwater system, which runs straight to streams and the sea. A contractor should block or protect the drains and send the water to unsealed ground or collect it.
The council's pressure washing and water blasting guide sets out the law. Under the Resource Management Act 1991 it is illegal to discharge any substance to water, stormwater or land unless a consent or plan allows it. Infringement fines reach $2,000 for an individual and $4,000 for a company, and both the landowner and the contractor can be held responsible.
On a typical driveway job the crew should:
- cover or bung the catchpits and grates on and near the driveway before starting
- use sand socks or similar barriers to steer water onto lawn or garden instead of the road
- pump or vacuum up water that pools against a covered drain
- hold off on moss treatments when rain is forecast, so they don't wash away before they work
It is a fair question to ask anyone you hire: how will you stop the wash water reaching the drains? If you ever see a spill going into a stormwater drain, the council's pollution hotline is 09 377 3107.
What water blasting costs
Published Auckland figures put water blasting at roughly $3.50 to $7 per square metre, which works out at about $200 to $400 for a standard double driveway. Small paths start lower and big driveways with paths can reach $550. Heavy moss, oil stains, steep sites and how the wash water has to be contained all move the price, so we confirm it after a look.
| Job | Typical range |
|---|---|
| Concrete driveway or path, priced by area | About $3.50–$7 per m² |
| Small driveway or path, up to about 30 m² | $120–$250 |
| Standard double driveway, about 30–60 m² | $200–$400 |
| Large driveway with paths, 60 m² or more | $300–$550 |
| Patio or courtyard | $150–$350 |
A guide only, built from figures New Zealand and Auckland operators and cost guides publish (checked October 2026). Heavy moss, oil stains, steep access and sealing add to the price. We confirm your price after seeing the property.
How a water blasting job runs
- Walk-through: the crew looks at the surfaces, checks for anything soft, painted or old, and tests a hidden patch.
- Protect: drains are covered or bunged, water is steered onto lawn or garden, and plants, cars and windows near the spray are covered or moved.
- Pre-treat: moss, algae and lichen get a treatment first, with time to soak in, and stains get a spot cleaner.
- Blast: flat areas are cleaned with a spinning surface cleaner in overlapping passes, with a wand only for edges, steps and corners.
- Rinse and capture: loose debris is rinsed toward the collection point, and pooled water is pumped or vacuumed up.
- Optional post-treatment: a follow-up moss treatment or a sealer, quoted separately, once the surface has dried.
Questions people ask about water blasting
Is it a good idea to pressure wash your roof?
No. High pressure can crack tiles, strip coatings, force water under flashings and, on older roofs, release asbestos, which WorkSafe says must never be water blasted. Pre-2000s roofs and decramastic tiles may contain it. Roofs are cleaned with a low-pressure soft wash and a treatment instead. Our roof cleaning service covers how that is done.
How do I get my concrete white again?
Treat it first, then clean it. A moss and mould treatment kills the growth that turns concrete grey, green and black, and a surface cleaner then lifts it evenly. Stains from rust, leaves or oil need their own spot cleaner. Very old concrete brightens a lot but rarely returns to the colour it was when new, because the surface has worn and opened up.
What do professionals use to clean concrete?
Most use a commercial water blaster fitted with a rotary surface cleaner for flat areas, a fan-tip wand for edges and steps, and a range of cleaners: a moss and algae treatment, an alkaline degreaser, and spot removers for rust and oil. Just as important is the containment gear, such as drain covers, sand socks and a wet vacuum, that keeps the run-off out of the stormwater.
How much does water blasting cost per m2?
Published New Zealand rates for driveways and paths sit at roughly $3.50–$7 per square metre incl. GST. Small jobs are usually priced as a flat job rather than strictly by area, so a short path costs more per metre than a big driveway. Heavy moss, oil stains, steep sites and sealing all push the price up.
Do I need to be home for water blasting?
Not usually, for driveways, paths and patios. The crew needs an outside tap that works, a clear area with cars moved off the driveway, and access through any side gates. We talk through the details when we ring to confirm the booking. If the job includes anything close to the house, it helps to have windows and doors shut.