Sandstone cleaning and sealing in Bilgola Beach

Bilgola Beach properties are built into a steep valley, and sandstone holds much of it together. Retaining walls create level platforms for houses and gardens, long flights of stairs connect them, and terraces take in the view toward the beach. On blocks near the sand, stone faces carry a pale, gritty film of salt and fine sand, and the edges of steps may be crumbling. Higher in the valley, under palms and trees, the stone is dark with mould and algae and slippery underfoot. Old dry-laid walls, where they survive, need especially careful handling. Our technicians inspect each zone, test cleaners on discreet patches, and agree a plan before starting.

Salt-laden stone is brushed while dry to remove loose deposits, then washed with fresh water and a mild cleaner at low pressure, so the weakened surface is not stripped. In the shaded areas, growth is sprayed and the biocide given a good while to reach the roots before soft brushes lift it away. Organic stains from palm fronds and leaves get targeted treatment or a poultice. Dry-laid walls are cleaned with minimal water so the soil and packing stones stay in place. Each terrace is bunded and rinse water is vacuumed up as we go, so nothing runs down to the street drains, the creek or the beach.

Sealing depends on where the stone sits in the valley. On the beach-facing terraces and stairs, which see both salt and people, we generally recommend an impregnating sealer that keeps salt water out yet still lets the stone breathe. Shaded stairs can also be sealed once they are completely dry, using finishes that keep their grip, though that may mean waiting several fine days. Retaining walls and dry-laid walls are left unsealed. We trial finishes side by side so you can see the colour before deciding, record the products applied, and suggest checking beach-facing stone each year and shaded stone every two years or so.