Washing a Melbourne House After Winter: What Builds Up, and the Order to Take It Off

Melbourne houses do not get dirty evenly. Come out of a wet winter and look at the place properly — not from the driveway, but from the side fence and the back corner — and the pattern is always the same. The north-facing front looks tired. The southern side, the one nobody walks past, has gone genuinely green. Somewhere there is a dark stain running down from a gutter joint that has been overflowing all season without anyone noticing.

Spring is a week away, and this is the point in the year when most people start thinking about it. The question worth answering first is not which machine to hire. It is what is actually on the house, and in what order it comes off.

What a wet winter leaves on the outside of a house

Four different things build up on a Melbourne exterior, and they do not respond to the same treatment.

• Biological growth. Algae, moss and lichen. This is the green or black film on render and the crusty patches on tiles and paving. It is alive, it holds moisture against the surface, and it has a root structure that goes into anything porous.
• Atmospheric grime. Traffic film, dust and general city fallout, bound onto the surface by months of rain and never washed off because nothing dried out long enough.
• Organic litter. Leaf fall, bark, seed pods and the tannin staining they leave behind on concrete and light-coloured render once they have sat wet in one place for weeks.
• Water staining. The streaks below an overflowing gutter, a split downpipe or a blocked outlet. These are not dirt in the usual sense; they are a record of where water has been going.

Only the last one is a warning about the building itself, which is why a wash is worth doing with your eyes open rather than just with a wand in your hand.

Why one side of the house is always the worst

The southern and south-eastern walls of a Melbourne house get very little direct winter sun. They stay cool, they stay damp for longer after every shower, and through June and July they may not fully dry for weeks at a time. That is exactly the condition algae and moss want, and it is why one wall can be thick with growth while the wall around the corner looks almost clean.

The same logic explains the other reliable trouble spots. Under a wide eave where rain never rinses but damp air sits. Behind a shrub grown up hard against the render. Along the bottom metre of a wall where splash-back off a path keeps it wet. Beneath a tree that drops litter and blocks the sun at the same time.

This matters practically, because it means the shaded side is not just dirtier — it has a different problem. The front of the house needs washing. The southern side needs the growth killed, or it will be back well before it should be.

Pressure is usually the wrong first question

The instinct is to reach for more pressure, and on a driveway that is fine. On the house itself it is generally the wrong tool, for a reason that is easy to miss: high pressure removes what is on the surface, but the growth on a porous wall is not only on the surface. Blast it and the wall looks transformed and then greens up again surprisingly fast, because the root structure is still in the render.

Meanwhile the pressure itself does real harm. It drives water behind weatherboards and into window reveals. It strips the coating off roof tiles. It cuts soft mortar out of older brickwork. It lifts paint on timber and it can force water through weep holes into the wall cavity, which is a genuinely expensive way to clean a house.

The alternative is soft washing: a treatment that kills the growth chemically, time for it to work, then a low-pressure rinse. This is covered in more detail in our comparison of pressure washing and soft washing, but the short version is that the chemistry does the work and the water only carries the result away.

The order the job is worked in

This is where most self-managed exterior cleans go wrong, and it costs nothing to get right. Every surface on a house sheds onto the one below it. Work in the wrong order and you clean things twice, or you finish the walls and then undo them from the roof.

Gutters and downpipes come out first, before anything is wet. Then the roof, because everything loosened up there runs down the walls. Then the walls, eaves and fascia. Then windows and frames, once the surfaces above them have stopped shedding. Paths, driveway and steps last, because they catch the entire job.

There is one refinement inside the wall stage that is worth knowing. Treatment goes on from the bottom up and rinsing comes from the top down. Applying downward onto a dry wall leaves narrow runs of clean surrounded by dirty, and those tramlines can set into render permanently.

What is worth checking while the house is wet

A wash is the one time in the year when someone is looking closely at every external surface, on a ladder, with water running. That is an opportunity, and it is the part of the day that pays for itself.

Worth noting as you go: where the gutter actually overflowed, which is obvious from the staining below it; whether downpipes are discharging into the stormwater system or just onto the ground beside the wall; whether weep holes at the base of brickwork are open or packed with dirt and mortar; whether any window seals have perished; whether mortar is crumbling anywhere it was previously sound; and whether roof tiles have slipped or cracked over winter.

Every one of those is a small job now and a much larger one after a summer of storms. It is also the reason we treat gutter cleaning as part of the same visit rather than a separate errand.

Why now rather than in the middle of summer

There is a practical case for doing this in the next few weeks rather than waiting for hot weather.

The growth is at its peak right now, at the end of the wet months, so this is the point at which removing it makes the biggest visible difference. Mild overcast days genuinely suit the work, because a treatment that dries out too fast in strong sun has less time to do anything. The gutters are still full of what autumn and winter put in them, and spring storms are the ones that expose that. And a wall that is cleaned now goes into its drying season clean, rather than spending another three months with a living layer holding moisture against it.

The house also stops being a background irritation. There is a particular kind of Melbourne fatigue that comes from looking at a grey, streaked, faintly green exterior for four months. It is worth more than people admit to have that gone by the first warm weekend.

Frequently asked questions

Is the end of winter too wet to wash a house?

It is one of the better windows. Mild, overcast days suit a soft-wash treatment because the solution stays wet on the surface long enough to work instead of flashing off in the sun. What matters is being able to work safely on a roof or ladder, so the job is scheduled around wind and rain rather than around temperature.

Will pressure washing damage render or painted weatherboard?

It can, and it is the most common avoidable damage we see. Render, painted timber, older mortar and roof tile coatings are all softer than the equipment is capable of. On those surfaces the growth is killed chemically and rinsed off at low pressure. Hard, sound surfaces like concrete paths and driveways are the ones that genuinely suit pressure.

How long before the green comes back on the shaded side?

Longer if the growth was killed rather than blasted off, but no treatment makes a permanently shaded, damp wall behave like a sunny one. The things that actually extend it are the ones that change the conditions — clearing gutters so water is not running down the wall, cutting back what is overhanging and shading it, and making sure downpipes discharge away from the surface.

Do the gutters have to be done at the same time?

They should be done first, in the same visit. Cleaning gutters after the roof and walls means dropping debris and run-off back onto surfaces that were just finished, and a blocked downpipe found in September is worth far more than one found after the first spring storm has already sent water down the inside of a wall.