Concrete cleaning in Canberra: every surface, and what it needs

"Concrete cleaning" covers a lot more than the driveway. Most Canberra homes have five or six separate concrete surfaces, each with a different problem and a different correct approach — and the cheapest way to deal with them is knowing which is which before anyone turns a machine on.

Why Canberra is hard on concrete

The ACT climate creates a specific combination you don't get in warmer coastal cities:

• Long, damp, shaded winters. Concrete that never gets sun between May and August stays wet for months, which is exactly what algae and black mould need.
• Hard frosts. Water sitting in surface pores and freezing repeatedly is what accelerates surface spalling on older or poorly finished slabs.
• Deciduous street trees. Oaks, elms and liquidambars through the established suburbs drop wet leaf litter that leaches tannin and leaves brown shadow stains.
• Dry, dusty summers. Fine dust drives into the pores and greys the whole slab evenly, so the deterioration is gradual and easy to miss.

Surface by surface

Surface	Usual problem	Approach
Driveway	Black mould, oil, tyre rubber, tannin	Full pressure, surface cleaner, pre-treat
Front path & steps	Algae — and a genuine slip hazard	Full pressure plus biocide; prioritise this one
Garage floor	Oil, tyre marks, dust	Degreaser first, then pressure
Patio & alfresco slab	BBQ grease, mould, food and drink stains	Degreaser, then pressure
Exposed aggregate	Mould in the texture	Reduced pressure, wide fan, chemistry-led
Coloured or stencilled concrete	Fading and mould	Low pressure only — pressure strips colour and sealer
Pool surrounds	Algae, sunscreen residue, slipperiness	Pressure plus biocide; see our pavers guide
Retaining walls & besser block	Mould, efflorescence	Soft wash — blasting erodes mortar joints
Old, spalling concrete	Surface already breaking up	Low pressure — pressure accelerates the damage

The one worth doing regardless of how it looks is the front path and steps. Algae on a walking surface is a slip risk, and it's the surface most likely to be wet and in shade.

The method that makes a clean last

The difference between concrete that stays clean for two years and concrete that greens up again by winter is entirely in the pre-treatment. Water force removes the visible growth; it leaves the roots. A biocide applied and allowed to dwell kills the algae properly, and only then does pressure become the tool that clears it away.

1. Sweep off loose leaf litter — blasting wet leaves spreads tannin.
2. Spot-treat oil with degreaser and iron staining with an oxalic-based remover, each with its dwell time.
3. Pre-wet, then apply the biocide across the whole area and let it work for 10–15 minutes.
4. Clean with a rotary surface cleaner in slow, straight, overlapping passes.
5. Detail edges, joints and drains with a 25° or 40° fan tip.
6. Rinse in one direction, and rinse down any walls you've splashed.

The step-by-step for driveways specifically, including how to avoid zebra striping, is in our driveway pressure cleaning guide.

Matching the stain to the fix

Concrete stains look similar and behave completely differently. Getting this wrong wastes a weekend:

• Black or green film — mould and algae. Biocide plus pressure.
• Dark greasy patches — oil. Degreaser or a poultice; pressure alone spreads it.
• Orange or rust-brown — iron. Oxalic acid; pressure does nothing.
• Chalky white — efflorescence, salts coming out of the slab. A mild acid wash, and it can recur.
• Brown shadows under trees — tannin. Biocide plus pressure, sometimes an oxalic assist.
• Black scuffs — tyre rubber. Degreaser and heat or hot water; it's a polymer, not a stain.

Timing it right

Spring and autumn are the best windows in Canberra. In mild weather solutions dwell properly instead of flash-drying, and the slab dries out afterwards. Avoid cleaning when a frost is forecast overnight — saturated concrete and freezing temperatures are a bad combination for an older surface. Mid-summer works, but you'll be fighting evaporation and re-misting constantly.

What it costs

Concrete cleaning in Canberra generally runs $150–$450, from around $149. It's priced per square metre past the minimum call-out, with adjustments for heavy staining and difficult access. Because most of the cost of any job is getting the equipment on site, doing the driveway, paths, patio and garage floor in a single visit is far cheaper than four separate call-outs — and it avoids the awkward result where one gleaming surface makes everything next to it look worse. Full ranges are in the Canberra cost guide.

FAQs

What is the best way to clean concrete?

Pre-treat with a mould-killing solution and let it dwell, then clean with 3000–4000 PSI through a rotary surface cleaner rather than a bare wand, then rinse. Chemistry does the lasting work by killing algae at the root; pressure removes what the chemistry has loosened. Skipping the pre-treatment is why some cleans go green again within months.

How much does concrete cleaning cost in Canberra?

Most residential concrete lands between $150 and $450, from around $149 for a small area. Pricing is per square metre once past the minimum call-out, adjusted for condition and access. Cleaning several concrete areas in one visit costs considerably less than separate bookings.

Can you clean concrete without a pressure washer?

For small areas, yes. A mould-killing solution, a stiff deck brush and a garden hose will handle a modest path, though it's slow and physical. For a driveway or anything with ingrained oil or tannin, you need the pressure and flow rate to make it practical.

Why does my concrete go green every winter?

Canberra's cold, damp winters and long shaded periods keep moisture sitting on concrete for months, and algae only needs moisture and a porous surface. South-facing and tree-shaded concrete gets the least sun and drying wind, which is why it greens first and worst.

Should concrete be sealed after cleaning?

It's optional but worthwhile. A penetrating sealer stops oil, tannin and iron soaking into the pores, so stains sit on the surface where they can be removed, and each future clean is faster. The concrete must be completely dry first — usually 24 to 48 hours after washing.

When is the best time of year to clean concrete in Canberra?

Spring and autumn. Mild temperatures let cleaning solutions dwell without flash-drying, and surfaces dry properly afterwards. Avoid cleaning during a frost or when one is forecast overnight, since water sitting in the surface pores and freezing is hard on concrete.