There is no single right answer, but there is a right way to think about it. The honest version is that it depends on four things: what your exterior is made of, how much shade it gets, what is growing near it, and how close you are to the water.
The rough baseline
For a typical Brisbane home in an average position, a full exterior clean every twelve to eighteen months keeps things stable. Driveways and paths often want attention a little more often because they collect traffic grime and take the most direct sun and rain.
That is the baseline. Most homes are not average.
What pulls the interval shorter
Shade is the biggest factor. A wall or roof section that stays damp into the middle of the day will grow mould and lichen several times faster than one that dries by nine. If you have mature trees over the roof or a south-facing wall that never sees direct sun, halve the interval.
Proximity to water is the second. Homes closer to the bay pick up salt haze, which sits on surfaces and holds moisture. Tea staining on metal and stainless is the visible symptom.
Surface porosity is the third. Unsealed concrete, sandstone and older render all absorb water and give growth something to root into. This is a large part of why sealing a driveway after cleaning extends how long it stays looking clean.
What pushes it longer
An open, sunny block with metal roofing, sealed concrete and no overhanging trees can comfortably go two years between full cleans. If that is your house, you do not need us annually and we will tell you so.
The test that beats any schedule
Look at the north and south sides of your house on the same afternoon. If the south side has visibly gone green or grey while the north still looks like paint, growth is established and it is time. Waiting from that point does not save money, because organic growth roots deeper into porous surfaces the longer it sits, and a deeply established colony takes more treatment to remove than a young one.
The other reliable signal is the roof, since it always goes first. If you can see patchy discolouration on the tiles from the street, the walls are not far behind.
Cleaning too often is a real thing
It is worth saying the other side. Unnecessary cleaning, particularly at high pressure, wears surfaces out. Every aggressive clean of a concrete tile roof takes a little more of the factory coating. If someone is telling you a domestic roof needs doing every year, ask why.
The right frequency is the longest interval that keeps growth from establishing, and no shorter.
If you are unsure where your home sits, send a photo of the shadiest wall and the roof. We would rather tell you to wait six months than clean something that did not need it.
