Setting the scene
This is an excerpt from an article in Sanctuary magazine issue 5.
The road to Michelle and Warwick Marshall’s home was shrouded in a heavy fog that seemed in no hurry to lift. A worrying sign, I thought, considering the entire house design had been driven by the property’s spectacular views. As I left the car, however, the mists began to clear, revealing tantalising glimpses of northern Sydney’s Garigal National Park and Middle Harbour.
Michelle and Warwick have lived on the site since 1999 when they bought a basic, brick-veneer weatherboard cottage. According to Michelle it was like living in a tent—hot in summer and freezing cold in winter—albeit one pitched in a great location.
“We fell in love with both the block and the bushland that surrounds it,” she says. “We’d always planned to renovate to take better advantage of the views, but when we brought our building designer Dick Clarke to the site, even though he prefers to work with the existing structure rather than demolish and rebuild, he reluctantly recommended rebuilding from scratch.”
The views drove the design, but it meant that the building would need to face away from the sun and require a combination of intriguing roof angles to maximise passive and direct solar access. Five years later, the new house sits perched at the edge of a six-metre sandstone platform with balconies cantilevered out into space to capitalise on the outlook to the south.
From the start, an important priority was minimising the building’s environmental impact and maximising its sustainable features, including the use of recycled and sustainable materials wherever possible. The original weatherboard house was given away, while its brick veneer was recycled as fill. Forty per cent of the concrete reinforcing was also recycled.
Building designer Dick Clarke says: “The project faced several challenges, including a council restriction on the height of the building, a structural issue regarding the balcony overhang, and serious concerns about the threat of bushfires, thanks to the home’s position at the top of a bushland escarpment.”
A bushfire’s intensity can double for every 10 degrees of slope, and research has shown that many houses survive the initial firefront only to succumb to burning embers igniting timber decks, eaves, gutters and window frames.
“With this in mind we opted to have no timber on the bush side (the balconies are suspended concrete slabs, rather than timber decks), as well as fire-rated finishes throughout the exterior and windows protected with screen inserts,” Dick says. “A cleared area below the house is also intended to help slow a bushfire’s momentum, while the gutters have been leaf screened, which has the added advantage of keeping the home’s rainwater supply clean.”
A dedicated fire-fighting reserve of 5000 litres of water is maintained at the bottom of the custom-designed in-ground concrete rainwater tank. It also has an outlet that the fire brigade can access in an emergency. The tank itself is concealed under a terrace, but is positioned away from internal floor areas. This provides a thermal break, keeping the cold rainwater away from the living floors. Similarly, the three concrete balconies are disconnected from the main structure of the house at the wall line, providing a thermal break to help control inside temperatures.
