Curl Curl sits between two headlands with the beach running roughly north–south and a lagoon system behind it. The result is a suburb where a lot of housing stock has a significant south-facing elevation, and south-facing walls in Sydney are the ones that never properly dry out.
Why south-facing matters more here
A north-facing wall in Sydney gets sun for most of the day year-round. It dries within an hour of rain. A south-facing wall gets almost no direct sun between April and September, stays damp for a day or more after rain, and in winter can stay damp more or less continuously.
Add salt, which holds moisture, and a south-facing rendered wall a few hundred metres from Curl Curl beach is effectively a permanently damp surface for half the year. That is ideal for black mould and green algae, and it is why these walls look dirty again six months after a wash while the north face still looks fine after three years.
This is not a sign the wash was done badly. It is the aspect. More: cleaning render without damaging the paint.
What actually helps
Three things change the outcome on a south elevation, and only one of them is cleaning.
Airflow. Shrubs planted hard against a south wall trap moisture. Cutting them back half a metre makes a measurable difference to how fast the wall dries.
Water management. Check that the gutter above the wall is not overflowing and that downpipes discharge away from the base. Most persistent mould on a lower wall is a water problem, not a cleaning problem.
Chemistry, not pressure. Biological growth has roots in the surface. Blasting it off at high pressure removes what is visible, damages the paint film, and leaves the spores. Correct soft wash chemistry kills the growth so regrowth starts from zero rather than from a surviving colony.
The lagoon and the flats
Behind the beach, the land around Curl Curl Lagoon and the playing fields is low and holds moisture. Homes backing onto this country get ground-level damp, insects, and faster growth on fences, retaining walls and the lower metre of any wall.
Timber fences in this area have a noticeably shorter life than those a few streets uphill. Where a post goes into the ground is where it fails, and no amount of washing the palings changes that. More: cleaning a shared boundary fence.
North Curl Curl’s headland homes
Up on the headland the problem inverts. Those properties get sun, wind and direct salt load, with very little shade. Growth is not the issue; salt on glass, metal and powder coating is. Two suburbs’ worth of maintenance problems within a kilometre of each other.
Roofs
Curl Curl’s post-war concrete tile roofs grow lichen on the southern pitch for exactly the reasons above. Lichen is the one to act on, because it penetrates the tile surface and holds water there. Left long enough it degrades the tile itself, and the repair is re-roofing rather than cleaning. More: roof cleaning.
A realistic schedule
South elevations: wash every twelve months. Accept that this is the cost of that aspect.
North and east elevations: every two to three years is usually enough.
Gutters: twice a year, and check for overflow staining on the wall below.
Roof: annual inspection, treat lichen early.
Fences and retaining walls on the lagoon side: inspect posts and footings annually.
See the Northern Beaches overview and the Sydney maintenance calendar.
