Use of timber

By the 1970s, the most common timber for house construction was pinus radiata.

Types of timber

In the 1970s, the most commonly used timber for residential construction was pinus radiata (pine), although heart rimu and Douglas fir were also used.

In some areas it was common practice to use heart rimu for bearers while the rest of the floor framing was pine. Trusses, when used, were commonly manufactured from Douglas fir.

Other exotic species milled in New Zealand included Corsican pine, European larch, western red cedar, redwood (New Zealand grown cedar and redwood were considered inferior to imported timber) and western yellow pine.

While rimu was still available, other indigenous timbers such as matai, miro, totara, kahikatea, tawa, red beech and silver beech were in short supply.

The following table sets out the range of timbers commonly used during the 1970s.

 

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Timbers typically used in 1970s housing

Timber

Characteristics

Uses

Indigenous softwoods
Rimu (red pine) Durable (except in wet conditions), fine texture, medium density softwood, easily split Limited use for framing, subfloor bearers and weatherboards. Common use for interior finishing, doors and windows (dressing grade, treated)
Exotic softwoods
Pinus radiata Moderately durable above ground, requires treatment General framing, subfloor framing, weatherboards (clears and finger jointed), sashes and doors, interior finishing (finishing grade)
Douglas fir (Oregon) Moderately durable above ground (heartwood only), knotty timber General framing especially roof trusses, exposed beams, rafters, flooring, sashes and doors, interior finishing
Imported Western red cedar Low density softwood, straight grain, coarse texture, good dimensional stability, weathers to silver-grey colour, dry sapwood susceptible to borer attack Weatherboards, interior finishing, sashes, doors
Imported redwood Moderately durable above ground Weatherboards, interior finishing, sashes, doors
European larch Moderately durable above ground, difficult to treat General framing, flooring, interior finishing
Corsican pine Moderately durable General framing
Exotic hardwood
Jarrah Excellent durability, medium hardness, easy to work Flooring, decking

 

 

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Timber treatment

From 1952, radiata pine framing treated with boron salts was available, the boron salt levels being higher than today. Boron treatment provided resistance to borer attack (see Borer, rot and mould) and also provided a degree of resistance to rot.

The 1970s saw the introduction of kiln dried H1 LOSP treatment which was an insecticide treatment only. This led to a reduction in the use of wet boric treated timbers. Between 1970 and 1980, H1 CCA treatment was also available.

Douglas fir framing was used untreated.