Bronte Park runs up a gully behind the beach, with trees, a creek line and steep sides. The homes on the streets facing into it, and those under its canopy, get much less sun than those facing the ocean. Walls stay damp, paths stay wet, and growth takes hold quickly.
What the data says
The Bureau of Meteorology’s long-term record shows Sydney’s 9am humidity averaging 74 percent from February through June, with March having the most rain days. In a shaded gully, damp lingers far longer than in open streets.
What grows where
Walls: green algae on render and paint, black growth on brick and sandstone. More: the green film on walls.
Roofs: moss and lichen on tiles under trees, particularly south and east faces. More: moss on roof tiles.
Paths and steps: algae and moss, which make them slippery. More: moss on concrete.
Timber: fences, decks and cladding grey and grow mould. More: timber deck cleaning and oiling.
Treating it properly
Soft washing applies a biocide at low pressure. It kills growth rather than blasting the top off, so it takes longer to return. Pressure washing removes the surface layer, damages render, paint, timber and old brick, and opens them to faster regrowth. More: house washing versus pressure washing.
Lichen in particular does not pressure wash off; it needs a biocide and time. More: lichen.
Protecting gardens and the creek
Gully gardens are lush, and the gully drains to the beach. Biocide must not reach waterways. Pre-wet plants, cover sensitive ones, rinse afterwards, and direct runoff to soil. More: pets, ponds and gardens.
When cleaning is not enough
If growth comes back within months, look for a water source: a leaking gutter, a downpipe discharging against a wall, soil or mulch piled against the base, or blocked weep holes and subfloor vents. More: weep holes and subfloor vents.
Prevention
Prune back vegetation from walls and roofs where you can. Keep gutters clear. Keep garden beds below the damp course. Clean shaded elevations on a shorter cycle than sunny ones, often yearly.
Timber decks and fences in the gully
Timber in shade stays wet and grows mould and algae, then greys and splits. Cleaning timber is done at low pressure with a timber-safe cleaner, because high pressure tears the soft grain and leaves a furry surface. Let it dry thoroughly, usually several days, before oiling. A moisture meter decides when, not the calendar. More: when to re-oil a deck.
Inside the house
Gully-side homes often have damp inside too: mould on bathroom ceilings, musty sub-floors, condensation on windows. That is a ventilation and moisture problem. Exterior cleaning will not fix it, but clear gutters, working downpipes and clear subfloor vents all help. More: mould on bathroom ceilings.
How often
Shaded gully-side elevations typically need soft washing every one to two years, against two to four years for sunny ones. Roofs under trees need a moss treatment every few years. Paths and steps need attention every year for slip safety.
See the Bronte maintenance calendar and our soft washing service.
