Small site no barrier to quality

This two-storey duplex with a shared common wall and a mirror-image floorplan makes best use of a small site, and was built in such a way that future owners could transform it to one large dwelling by simply putting doors in the common wall. It’s one of 20 compact New Zealand properties showcased in Catherine Foster’s Big Ideas for Small Houses.

Mitchell Coll's determination to embed a sense of longevity into the buildings he designs is as much romantic as it is hardheaded and pragmatic.

He grew up roaming the South Canterbury back-country and spent many a happy holiday overnighting in the simple hunting cabins that dot the landscape. While doing so, he grew to appreciate not only their sheltering presence in an often intimidating landscape, but also how they met that need: "They’re so utilitarian — hard-wearing and functional. They’re designed to wear in over time, not wear out. I’m firmly of the belief that a national building code that requires buildings to have only a fifty-year lifespan needs upgrading."

These values informed both the design and every millimetre of the construction of the small, intriguing building on the edge of Christchurch’s CBD that earned Coll the Supreme Award in the 2017 ADNZ/Resene Architectural Design Awards and a shared award for a residential multi-unit development, among others.

Described by the judges as "an exemplar of urban living", its duplex mirror-image homes (connected back-to-back along a shared common wall) are snugly packed on to a narrow 300sq m site and, at only 74sq m each over two storeys, can definitely be described as compact.

Building two homes on a section where one would have been the norm is a strategy as carefully considered as the houses themselves. Coll explains the thinking behind this: "When we looked to build a home for ourselves, we wanted to show you can live well in a small house — and with enough storage and attention to both the scale and the detailing, it doesn’t have to feel like a small house.

"Building two houses arose from the fact that we only needed a small home on a site half this size, but as this was the site we had, you could say I designed to the site."

As a long-time participant in the Christchurch-based Superhome movement, Coll also wanted to demonstrate that new homes can be warm, dry, low maintenance, efficient to run, and can be built for no more than the average-sized architecturally designed home.

"I’ve always been interested in designing with cost efficiency in mind. It means I have to consider every element, whether they be the materials used, the type of construction, the structural elements — every square metre has to justify its existence.

"By building a house small and design-dense, the money saved can be spent on quality. The maths aren’t complicated — if you halve the size, you get twice the quality and the overall price, which is what really matters, is still low."

The impression of quality is immediate, even though the form — steeply gabled, and very nearly twice as high as it is wide — is as straightforward as that of the cabins that inspired it. It is the juxtaposition between this simplicity and the challenge posed by the cladding materials of Cor-Ten steel and wide-tray roofing iron that gives pause for thought.

Inside it soon becomes apparent that this hesitation is warranted. With every millimetre carefully planned to enhance the impression of space, the detail is impressive. High ceilings, concealed storage, bedroom ceilings raked and inset with skylights, recessed LED lighting and negative-detail shadow lines in place of architraving — all these strategies reduce visual clutter. The honey tone of the cross-laminated timber (CLT) structure and the pine plywood linings acts as a single linking colour and dominates the space, but eggshell blue on the kitchen island bench and black or navy accents throughout provide pops of definition and drama.

The floor plan is uncomplicated: two bedrooms, a bathroom and powder room are upstairs, and a combination living, kitchen and dining space downstairs. Large wrap-around decks under cantilevered roofs connect these living areas to the gardens and, despite the close proximity of the neighbours, each enjoys total privacy from the other because of how Coll has positioned the entrances and access to the rear unit.

The rear unit is rented out and contributes to the mortgage, and although at present the front house fulfils every one of Coll and his partner Amy’s needs, future proofing was a consideration. Doors cut through the party wall would allow the two dwellings to become one large family home (this would require a building permit as it’s a fire-rated wall, and an encumbrance added to the title). Should use of the site change in the future, the two homes could be uncoupled and moved intact without the need for radical deconstruction.

In the case of the unthinkable happening — earth movement from another earthquake — the foundation system means that the houses could be relevelled quickly and efficiently.

Although it is a resolutely urban addition to the Christchurch rebuild, Coll has got his trusty cabin. "We’ve got the best of all worlds. It’s strong, handsome, easy to live in — and right in the heart of the city."

AT A GLANCE

Duplex houses on one site, one providing a home, the other a long- term income stream.

Each house is 74sq m.

Location: Madras St, Christchurch central.

Architect: Mitchell Coll, Coll Architecture.

Site size: 306sq m.

Builder: Feutz and Goldsmith Builders Ltd.

Costs:
- Land: $215,000.
- Build: $361,000 per house. ($4878 per square metre); $722,000 in total.
- Landscaping: $57,000.
- Fees and compliance (including. surveying and engineering fees, subdivision costs and building permit; no development contribution required; excluding architectural fees): $47,000.
- Total: $1,041,000 (all costs divided between two houses).