Sandstone cleaning on the Northern Beaches

On the Northern Beaches, the dirt on sandstone usually tells you which way the property faces. Ocean-facing walls and terraces carry a grey film of salt and fine sand, and the stone often feels gritty where salt has started to work at the surface. Harbour and Pittwater sides stay damper, so green algae and black mould take hold on steps and sea walls. Lots that back onto bushland collect leaf litter, and wet leaves leave brown tannin shadows. Lichen settles on capping stones and the tops of retaining walls almost everywhere. Each responds to a different treatment, which is why we identify them before choosing a cleaner.

Plenty of sandstone in the region has already been cleaned the wrong way. Weekend pressure washers leave pale stripes and a furry surface, and on salt-weakened stone a close jet can strip a surprising amount of face in one pass. Acid-based brick cleaners react with the iron in Hawkesbury sandstone and leave orange staining that outlasts the dirt. Our technicians start with a test patch, apply a stone-safe biocide to kill growth at the root, give it time to dwell, and then rinse it off gently, using warm water where grime is greasy. The stone comes back to its own colour and banding without being worn down.

Wash water from a stone clean carries detergent, biocide and grit, and on the Northern Beaches the nearest drain is never far from a beach, a lagoon or Pittwater. The work area is bunded, and the run-off is vacuumed up and taken away for proper disposal. Steep sites get the same care: on a long flight of stairs we start at the top and catch the water at every landing before moving down. Once the stone has dried, which can take several fine days on a shaded slope, we will tell you honestly whether sealing is worth doing or whether a maintenance clean every year or two makes more sense.

See the full method on our sandstone cleaning page.