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Expressive canopy crowns a New Zealand home

January 1st, 2008 / By: / Exteriors, Feature

The canopy that crowns Noble House on New Zealand’s Great Barrier Island invites poetic comparisons — a wind-carved dune, a sea-polished shell, a gull in swooping flight — but its form was born strictly from function.

Designed and now inhabited by architect Greg Noble of GeorgiGregg Ltd., the 186m2 Noble House overlooks a beach at the mouth of a tidal estuary on large but sparsely inhabited Great Barrier Island. Native bush surrounds it.The site presented a laundry list of challenges. “Severe exposure to wind and salt spray,” says Murray Higgs, managing director of fabric engineering and design firm Structurflex NZ, the company that engineered the tensile membrane canopy. “No road access across the estuary. No public supply of electricity, water or gas. Sometimes impassable with high tides or storms.”

To top it all off, during the time the house was being built (January-November 2003), the site had no phone links or cell phone reception.

Despite its fantastical appearance, the canopy was an eminently practical choice for the demanding site. A German-made PV/PES membrane, the fabric roof is lightweight, rolls into a small bundle for easy transportation, is able to withstand the stresses of wind, water and salt, and allows a high level of diffused sunlight into the house.

“The membrane’s ability to tension-fit was also of assistance,” says Higgs, “in meeting the compound curves of the building’s hemispherical form and as a monolithic covering without problematic joints or openings.”

According to Higgs, the most difficult part of the project with regards to the membrane structure was prefabricating the structural steel frame. The frame included large spans rolled to both constant radial curves and elliptical curves, all fabricated to the tight tolerances necessary to ensure problem-free assembly.

This difficult task was fulfilled “brilliantly” (says Higgs) by ACME Engineering of Wellington, with the support of Auckland-based firms D.J. Shilton and Compusoft, specializing in structural and membrane engineering, respectively. The frame cost $130,000 and took three weeks to assemble.

Local builders Offshore Homes Ltd. built the conventional lower portion of the house. Structurflex designed the building and made arrangements for local engineers, products, and services from its office in the UK, where the company was based at the time. “Our arrival on site coincided with the building’s arrival on the island by barge.”

The barge was only the beginning of the transportation process. “Unloading it, getting it to the beach and across the sand dunes and tidal estuary to the site was a feat of local ingenuity. Better still was leading the site operation through a two-or three-week period of total disbelief that any three-dimensional form could result from a bundle of steel and a sack of ‘tent’ cloth,” says Higgs.

The membrane cost $110,000, including all fittings and structural steel hold-downs. Installation took four days and went off “without a hitch or a ripple or a seam out of place,” said Higgs, “thanks to Harry Klein and Structurflex Auckland.”

“To see the rise of the first self-supporting steel ribs,” he continued, “and finally to see the membrane being tensioned to such an expressive dynamic — this was by far the best bit of the project.”

Shelby Gonzalez is a U.S.-based freelance writer specializing in environmental issues.

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