House frames are usually constructed in efficient, hi-tech factories. Times photos Jackie Russell.

MAKING choices about building a house is a challenging process. Homeowners have to consider how many bathrooms they need or what colour the walls will be, as well as worrying whether their new habitat is saving or slaughtering the planet.

The framework of a house is often taken for granted by its occupants, but it forms the very skeleton of the structure and is an important component of efficient construction and sustainability.

Most New Zealand houses are constructed with timber frames. This may be a legacy from early settler days when there was an abundance of native timber throughout the nation. Interestingly, the earliest colonialists with a few bob in their pocket imported kitset homes from Australia and if this was too expensive only the timber frame was sent to New Zealand. Kauri weatherboards, now a precious commodity, were used to clad these villas and bungalows.

Harvesting of the abundant timber resource boomed, but the leaders of the era recognised the native forests would soon be exhausted. By the end of the 19th century the government had planted the first exotic tree plantations. Ideal growing conditions for pinus radiata made it a popular and cheap choice for Kiwi builders in the post World War 2 construction boom. Untreated pine was the common framing timber but soon preservative treatments were sought.

The good old days of builders cutting and constructing entire frames onsite and tossing waste to the roadside for home fires are long gone. Frames and trusses are now designed by draughtsmen and manufactured in efficient factories.

East Tamaki specialist Smith Timber ITM has manufactured pre-cut and pre-nail frames and trusses for nearly 30 years, starting out in Hawke’s Bay. By the end of the 80s, director Neville Smith had established his company in South Auckland and this year the team moved to a purpose built factory and yard in Greenmount Drive.

Neville says: “Ninety-five per cent of all houses are still built with timber wall frames.”

Growing demand for sustainable building practices has changed the company’s operations during the past three decades, but the use of the natural resource, timber, remains a core principal.

The World Green Building Council estimates buildings and communities are responsible for more than 40 per cent of greenhouse gas emissions into the Earth’s atmosphere.

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Timber off-cuts are recycled when ever possible.

This begs the question: How environmentally friendly are timber frames and trusses?

Advocates of natural building say using timber rather than man-made or industrial materials has to be a positive. And, they recommend building techniques that minimise the use of products requiring substantial energy for their manufacture or transportation.

Modern frames may contain chemical cocktails to preserve them, but timber is an effective way of storing carbon dioxide absorbed by trees. In fact, this applies to all timber products, from lovingly crafted wooden furniture to a basic breadboard. Importantly, harvested plantations need to be replanted to continue absorbing carbon

emissions, but for the past few years new forestry planting and replanting rates have decreased in New Zealand.

Minimising waste is important to reduce both expenses and resource depletion. Ensuring house plan meets the occupants’ needs before the first length of timber is cut is essential. Alterations during construction wastes time, money and materials.

Using a pre-nail factory reduces costly errors and waste with materials used as efficiently as pos-sible. At Smith Timber ITM waste is sorted, ensuring correct disposal or recycling when possible.

Treated timber waste should be disposed of into landfill where it is buried. It should not be burnt in open fires, stoves and fireplaces, and confined spaces.