How often should a roof be cleaned?
Every two to four years for most Sydney roofs. Heavily shaded, tree-covered or coastal roofs sit at the two-year end; open, sunny roofs stretch toward four. Because a proper soft-wash treatment keeps suppressing regrowth for seasons after the visit, the interval usually lengthens after your first clean. The tell-tale signs you are due: moss in the valleys, and darkening on the south face.
Two to four years, and what moves the dial
Most Sydney roofs want a proper clean every two to four years. Where yours lands in that window comes down to three things: shade, canopy and salt. A roof in full sun dries fast, and moss and lichen struggle to get established on a dry surface. A roof under gums or jacarandas is a different proposition — it stays damp, collects leaf litter, and feeds growth quietly through every winter. Trees are the single biggest factor, more than the age of the roof.
The coast pushes you toward the two-year end too. Salt air holds moisture against the surface longer, which is exactly what growth wants. So a shaded roof near Middle Harbour is a two-year roof. An open, north-facing roof on a dry ridge can comfortably go four. Neither number is a guess — it is simply how fast the growth returns, and you can read it from the footpath without climbing anything.
The treatment keeps working after we leave
A proper roof clean is not just a rinse. The soft-wash treatment kills moss, lichen and algae at the root, and it keeps suppressing spores for seasons after the visit. The dead material then sheds gradually with the weather rather than being blasted off — which is precisely what you want on tiles and coated steel, where high pressure does more harm than the grime ever did.
This is why the cadence stretches. The first clean of a long-neglected roof is the big reset: established colonies take the most work to remove. Every clean after that starts from zero rather than from a settled colony, so regrowth is slower and the second interval is usually longer than the first. Keep the rhythm and the roof never gets back to where it started. Skip a cycle and the clock rewinds.
Two signs your roof will give you
First sign: moss in the valleys. Valleys are the last part of a roof to dry — they channel every drop of water and collect whatever the trees let go of. Moss shows up there before anywhere else. If the valleys have gone from clean metal or tile to a green cushion you can see from the street, the roof is due. Not urgent, not an emergency. Due.
Second sign: the south face going dark. In Sydney the south side gets the least sun, dries slowest, and grows algae first — it reads as a grey-green or black shadow spreading across the tiles. Compare the south face with the north from the ground. If one side looks distinctly darker than the other, that is growth, not shade, and it is telling you which end of the two-to-four-year window your roof lives at.
What a clean will not fix
Some honesty before you book anything. Cleaning removes growth, grime and staining. It does not repaint. A Colorbond roof whose colour has chalked with age will come up clean but still faded. Cracked tiles, rusted fixings and failed pointing are a roofer's job, not a cleaner's — and if we find them up there, we will tell you rather than wash around them.
There is also a case for not waiting. Lichen anchors into the surface it grows on, and a colony left for years can leave a faint footprint on tiles even after it is properly removed. That is the real argument for cadence over rescue: a roof cleaned every two to four years never gives lichen the time to dig in. The cheapest clean is the one that stays ahead of the growth.
Put a number on yours
Roof cleaning is quoted per job — size, pitch, growth, access and material all move the number, and no two roofs match — so we do not publish a flat rate. The instant quote asks a few questions about your place and returns a firm, bookable price in about 60 seconds. It holds unless the roof is materially different from what you told us. No ladder salesman, no inspection theatre.
If the valleys are growing moss or the south face has gone dark, get your number now and pick a date. Bundling the gutters onto the same visit saves 5–15%, and they are usually overdue together. Then put the next clean in the diary: two to four years out, closer to two if you live under trees or near the water. The roof will confirm the schedule for you.