A green, slippery driveway is a Wellington classic. Steep, shaded and damp for half the year, it grows moss and lichen like a lawn. Sooner or later someone hires a water blaster for the weekend and has a go.
That can work fine. It can also leave you with a striped driveway, sand blown out of your pavers and a sore back. Here's what to know before you start, and when it's worth getting us in.
Why Wellington driveways get so slippery
Most of the slime on a driveway is moss, algae and lichen. It loves shade and damp, and Wellington has plenty of both. A driveway on the south side of a hill might barely see the sun from May to September. Add leaf litter from overhanging trees and you've got a green film that turns into an ice rink in the rain.
On a steep driveway, that's not just ugly. It's how people slip and cars lose grip.
Can you water blast it yourself?
Yes. Concrete, pavers, asphalt and brick are all surfaces that can handle a water blaster. Plenty of people do a decent job on their own driveway.
But there are a few traps.
Stripes and etching
The most common mistake is holding the nozzle too close, or using a pin-jet tip. It cuts lines into the surface of the concrete. When it dries you get a zebra pattern that's often worse than the dirt was. Keep the nozzle moving, keep a steady distance and overlap your passes.
Blowing out paver joints
Pavers sit on sand, with more sand in the joints. Blast straight down the gaps and you'll wash the joint sand out. The pavers can then move and weeds move in. Work at an angle and re-sand the joints afterwards.
New concrete
If your driveway is less than about three years old, don't water blast it. The surface is still hardening. Soft wash it with a cleaning solution instead.
Steep slopes and wet surfaces
Wellington driveways can be seriously steep. Once you've wet down a mossy slope, it's at its most slippery. Work from the bottom up, wear shoes with grip, and keep the hose behind you so you don't trip on it.
Where the water goes
Stormwater drains in Wellington flow to streams and the harbour, not to a treatment plant. Plain water and loosened moss is one thing. Don't let detergents, degreasers or oil run straight into the drain.
The moss comes back fast
Here's the catch with water blasting moss off a driveway. Water alone strips what you can see but often leaves the roots. In a shaded spot it can be back within months.
That's why we treat the surface as well as blast it. A cleaning solution goes on to kill the growth, then the water blaster lifts it off. The result lasts much longer than plain water.
Oil, rust and tyre marks
Moss is easy compared with oil. A water blaster on its own rarely shifts an old oil stain. It needs a degreaser and some dwell time first. Rust marks from garden furniture or a leaking pipe need a different treatment again. If you've tried and the stain's still there, it's probably not coming out with water alone.
When it's worth getting it done professionally
Get someone in if:
- The driveway is long, steep or awkward to work on
- You want the moss killed, not just knocked back
- There are oil, rust or tyre stains to shift
- You're selling and want the place looking its best
- It's newer concrete or exposed aggregate you don't want to damage
- You'd rather spend your Saturday doing something else
We do driveways, paths, patios and other concrete across Wellington, the Hutt Valley and Porirua. See our pressure washing in Wellington page for what we clean, or our driveway and concrete cleaning page for more detail on stains.
How often should you do it?
Once a year keeps most driveways safe and tidy. Shaded, steep driveways might need it more often. A sunny, flat one can go longer. Late spring is a good time, once the worst of the wet is over, so it stays clean through summer.
Don't forget the house
If you're cleaning the driveway because the place is looking tired, the walls are probably due too. The house itself should never be water blasted. Painted weatherboards and plaster need a low-pressure soft wash with a solution that kills the mould. We can do both on the same day.
Prices depend on the area and how bad it is. Call us on 027 303 8398 for a free quote. We're open seven days, 7am to 7pm.
Driveway water blasting questions
Will water blasting damage my concrete driveway?
Not if it's done right. Damage usually comes from holding the nozzle too close or using the wrong tip. New concrete under about three years old should be soft washed instead.
How long does a clean driveway stay clean?
If the moss is killed with a solution as well as blasted, it lasts much longer than plain water. Expect to redo a shaded driveway about once a year.
Can you get oil stains out?
Often, yes. Oil needs a degreaser and time to work before it's blasted. Very old stains may fade rather than disappear completely.
Do I need to be home?
Not necessarily. We'd suggest being around at the start to walk through the job, and at the end to check you're happy.