My name’s Dave, and I’ve spent close to twenty years sealing, patching and occasionally swearing at concrete driveways around Wellington’s hill suburbs — Khandallah, Karori, Ngaio, the lot. My brother-in-law lives up in Khandallah, on one of those steep sections where the driveway runs down to the garage like a boat ramp, and every second winter he rings me to complain that his concrete’s gone green and slippery. Every time I tell him the same thing: it isn’t the concrete that’s failed, it’s the fact that nobody’s touched it since the day it was poured. Out here on the block I’ve sealed a fair bit of concrete over the years, and in a wet region the difference between a drive that lasts thirty years and one that starts flaking at ten comes down to a couple of jobs most people skip.
Why Wellington’s wet hills chew through concrete faster
Concrete is porous. It looks solid, but it drinks water like a dry sponge, and in a place that gets the kind of rainfall Wellington’s western hills cop, that water’s always working on it. When it soaks in and the temperature drops overnight, the water expands a fraction as it chills and pushes the surface apart from the inside. Do that a few hundred times a winter and you get classic surface scaling, where the top few millimetres start lifting off in little flakes.
Add a shady, damp section — plenty of them on the steeper Khandallah and Ngaio sections — and you get the other problem: moss, lichen and that black-green algae film. It’s not just ugly. On a sloped drive it turns the surface into a skating rink, and I’ve heard of more than one person coming a cropper carrying the shopping in. Sealing slows the water down, and regular cleaning keeps the growth off. Neither job is hard. Both get skipped.
Cleaning before you seal — the step everyone skips
You cannot seal dirty concrete. Whatever you paint over grime, you’re just gluing the grime down. My routine’s straightforward:
- Sweep it, then hit it with a stiff broom and a bucket of warm water with a splash of dish soap for the everyday muck.
- For moss and algae, a proper moss-and-mould treatment left to sit does more than blasting away with a waterblaster. If you must waterblast, keep the nozzle moving and don’t gouge the surface.
- Oil stains from the car need a degreaser and a bit of scrubbing before anything else. A cat-litter poultice pulls fresh oil out surprisingly well.
- Let it dry properly — two or three fine days, not one.
I do my own cleaning, but if you’re not confident on a slope, paying a tradie is money well spent — a standard double drive runs somewhere around $250 to $500 including GST, depending on how bad the moss is.
Picking a sealer that won’t turn your slope into a skating rink
For our climate I lean toward a penetrating sealer over a glossy topical one. Penetrating sealers soak in and repel water from within, so they don’t peel and they don’t go glassy and slick underfoot. The film-forming ones look sharp for a season, then wear off in the traffic lanes and turn slippery when wet — the last thing you want on a hill.
You’ll pay roughly $80 to $180 including GST for enough decent penetrating sealer to do an average driveway, applied with a roller or a garden sprayer on a dry, still day — two thin coats beat one thick one. If you’d rather not do it yourself, you can find concrete services near Mornington who’ll clean and seal a standard drive for around $600 to $1,200 including GST, all up.
| Job | Typical cost (incl. GST) | Notes |
|---|---|---|
| Pressure-cleaning a standard double driveway | $250–$500 | Price climbs with moss and algae buildup |
| Penetrating sealer, DIY, average driveway | $80–$180 | Two thin coats, roller or garden sprayer |
| Professional clean + seal, standard drive | $600–$1,200 | Covers cleaning plus two coats |
| Minimum cure before sealing new concrete | 28 days | Often longer through a wet winter |
| Resealing interval, sheltered drive | 2–3 years | Confirm with the water-bead test each autumn |
| Resealing interval, exposed or shady drive | 1–2 years | Shaded, damp sections need checking more often |
Whether you reseal every year or every three depends on how exposed the drive is, but a quick water test tells you: flick water on it, and if it soaks straight in rather than beading up, it’s time.
Cracks, joints, and when a patch isn’t enough anymore
Hairline cracks are normal — concrete moves. The trick is not letting water get into them and start the freeze cycle underneath. Rake out any debris, then run a flexible concrete crack filler along them once a year. Where the drive meets the garage or a path, keep that expansion joint topped up with a self-levelling sealant so water can’t track down the edge.
For control-joint questions on any new pour, the guidance on the government’s Building Performance site is a sensible starting point before you ring anyone. And if you’re weighing up a full replacement versus a different surface altogether, it’s worth reading about permeable paving in high-rainfall regions before you commit — in a wet spot it can save you a lot of grief with runoff.
Questions I get asked on the job
How much does it cost to clean and seal a concrete driveway in Wellington? Cleaning a standard double drive runs about $250 to $500 including GST. Sealer for a DIY job is another $80 to $180. Get a tradie to do the lot — cleaning and two coats — and you’re looking at roughly $600 to $1,200 including GST, depending on condition and access.
My driveway’s surface has started flaking — do I need to replace it, or can it be patched? Light surface scaling can usually be cleaned back, patched and sealed rather than replaced — I’ve saved plenty of Khandallah drives that looked worse than they were. If the flaking’s gone deep enough that you can see aggregate lifting out across large areas, or the cracking runs through the slab rather than just the surface, that’s a re-pour, not a patch.
What sealer should I use on an older, exposed-aggregate driveway? Stick with a penetrating sealer rather than a film-forming one. Older exposed-aggregate surfaces have more texture and more pores for a topical sealer to peel off, and a glossy finish on aggregate gets slippery fast once it’s wet.
Can I seal a brand-new concrete driveway straight away? No. Fresh concrete needs to cure and dry out first — usually around 28 days minimum before sealing, often longer in a damp winter. Sealing too early traps moisture inside and can cause the surface to blister.