Sandstone and travertine care on the Northern Beaches

The Northern Beaches sit on Hawkesbury sandstone, the porous Triassic quartz sandstone that forms Sydney's coastal cliffs and headlands. You can read it in the landscape: the hills that wrap around the southern side of Curl Curl, the sandstone heath of Stony Range in Dee Why, which grows on a former quarry site, and the rocks of Little Head at the far end of Palm Beach. Builders used what was underfoot. Most of Most of Palm Beach's early houses used local sandstone, Careel House at Whale Beach was built in 1931 from blocks quarried on its own site, and St Patrick's Seminary in Manly remains the region's best-known sandstone landmark.

Few parts of Sydney put stone under as much salt. The peninsula runs between the Pacific and, depending on where you are, Middle Harbour, North Harbour or Pittwater, so many homes catch spray from one side and humid estuary air from the other. UTS research on Sydney sandstone names salt as one of its main enemies in coastal areas: salty moisture enters the pores, dries out, and leaves crystals that grow and prise the grains apart. The result is flaking faces, powdery white bloom and pool coping that turns sugary at the edge. Storms add to it. Beachfront houses at Collaroy lost backyards in the June 2016 storms.

Beyond salt, the problems follow the landscape. Bushland lots near Garigal National Park, Dobroyd Head and Ku-ring-gai Chase drop leaves that leave tannin stains and keep walls shaded and damp, which suits black mould and lichen. Steep blocks mean long runs of sandstone stairs and retaining walls that rarely see full sun. Newer homes near the beaches often pair sandstone walls with travertine pool surrounds and terraces, and travertine has a weakness of its own: it is a limestone, so the acid cleaners many people reach for etch it. We plan every job around which stone is present and what is actually attacking it.

The whole region falls within Northern Beaches Council, whose administrative centre is in Dee Why. Heritage controls vary from street to street. Manly has mapped heritage conservation areas, including the Town Centre around The Corso and a Pittwater Road area, while elsewhere individual houses, gardens and structures can be listed as heritage items in their own right. If your property is listed, check with council before restoration work. Our technicians travel from Double Bay: Manly is roughly half an hour away off-peak and Palm Beach over an hour, both estimates. Every job starts with a test patch, uses low pressure and recovers wash water rather than letting it reach the street.