When Paul and Jaki Halliday decided to leave London’s traffic-clogged rat’s maze for the hills of New South Wales, they celebrated by commissioning their ideal home. Martin Spring explains how their compatriot, Alan Higgs, designed it

What a release for Alan Higgs! After 17 years in London, which has left him running a four-person practice in a Victorian garret overlooking the one-way traffic canyon in the West End, he has been commissioned to build a standalone family house in the endless wooded hills of New South Wales between Canberra and Sydney.

For Paul and Jaki Halliday, the release has been even sharper. Like Higgs, the Australian couple have spent years living and working in London. Unlike Higgs, who remains embedded in Seymour Place, they have returned to their homeland and now occupy the house they commissioned.

The architect’s understandable reaction to the boundless natural landscape has been to let the house spread out as three separate pavilions. “It consciously occupies a larger plan than it needs to,” he says.

This expansive tendency is well matched by a generous budget that has provided some 500m2 of accommodation. Two of the pavilions contain sizable living spaces – one with an upper floor of bedrooms – while the third pavilion, lying beyond a lawn and swimming pool, houses stables, a shed and a bedsit. The two habitable wings are linked by a short passageway containing the main entrance. The H-shaped configuration shelters a timber verandah deck from the wind.

Although the layout is relaxed, informal and freewheeling, the architecture is anything but. All three pavilions lie on the same axis and they are all oblong with steep, double-pitched roofs. The pure, symmetrical geometry of the forms is distilled further by crisp, unfussy detailing.

The simple forms were influenced by the agricultural tradition of sheep-shearing sheds and shelters in the Australian outback, says Higgs. Their simple geometry is also in the European modernist tradition. Even more deeply European than that, Higgs alludes to the manner in which English country houses dominated their surrounding country park.

“The silhouette of the Halliday house gives it an emphatic presence in its domain, although in a longer, lower and less grand manner,” he says. “In this way, it engages with rugged Yass River valley.”

How the earth was moved …

The last thing you would expect the Halliday house to be built of is rammed earth. Its rectilinear Miesian architecture with flat planes and crisp detailing is the antithesis of this prehistoric material, which conjures up oversized earthenware pots.

This rammed earth, it transpires, is slightly different. It is basically sandstone ballast made up 60% of gravel, up to 15mm in size, and 30% of sand. The clay content, which in Britain is taken as the basic binding agent, amounts to only 2-3% by volume, and its place is taken by a 10% admixture of cement.

What these ballast walls share with genuine rammed earth is their construction method. The ballast is applied as a dry mix and rammed within grp formwork.
“Basically, we are building roads between formwork,” quips Nick Gubbins of trade contractor China Walls. “That’s because it’s a dry mix of gravel, just like that used for the sub-base of a road, though stabilised with the cement admixture.”

The solid walls are just 300mm thick and unfinished. Steel reinforcement is only needed above window and door openings wider than 1.5m.

Architect Alan Higgs compares the self-finish inside and out with honed sandstone. “The beauty of the product is that what you see is what you get,” adds Gubbins, and this constructional honesty fits in well with Higgs’ modernist design approach.

The high thermal mass of the solid walls plays a role in passive solar design geared to the temperate climate of southern Australia. The walls collect solar heat through the day and radiate it into the house through the night.

Gubbins admits the stabilised ballast system would need some modification for the cooler, damper British climate. “To make a thermally insulated wall, you would build it in two vertical layers divided by a rigid panel of closed-cell polyurethane foam 40mm thick,” he says.

“Because it was built on the other side of the world with the client as owner-builder, we made the design idiot-proof,” continues Higgs. “My priority is to spend money on volume and space, not on tricky detailing. Anyway, Australian trade contractors work together in a more collegiate way than in Britain.”

Despite the long-distance design, the amateur construction management and the remote location, the house was designed and built in 14 months from the date the site was selected. As Higgs himself says, that’s not a bad achievement.