By the late 1940s, exotic timbers such as pinus radiata and Douglas fir were replacing native timbers.
Up until the 1950s, houses in New Zealand were built from a range of native timbers. But by the late 1940s, native timber supplies were dwindling so the building industry turned to the exotic timbers that had been planted in large quantities in the 1920s. Two of the most successful species were pinus radiata and Douglas fir, which were both found to be versatile and have a wide range of building applications.
From1953 onwards, pinus radiata had all but replaced the use of native framing timbers in many parts of the country. One exception was Otago where native timber framing was commonly used until the early 1960s. Radiata pine was used untreated until 1952, when boric treatment of was introduced.
Interior finishing timber was still typically rimu through this period.
By the 1960s, exotic species milled and available in New Zealand included Corsican pine, European larch, western red cedar and western yellow pine.
The table below sets out the range of timbers commonly used from the1940s through to the 1960s for state and private housing construction. It describes their characteristics and where the timbers were typically used.
|Rimu (red pine)
||Durable (except in wet conditions), fine texture, medium density softwood, Increased use of sapwood which was less durable and more prone to borer attack||General framing, weatherboards, flooring, interior finishing, doors and windows (dressing grade, treated sapwood)|
|Matai (black pine)||Moderate durability, above ground use only, prone to splitting
||Flooring, sub-floor framing, weatherboards, exterior joinery, interior finishing
|Douglas Fir (Oregon)||Moderately durable above ground (heartwood only), knotty timber||General framing, exposed beams, rafters, interior finishing, window joinery, doors
||Flooring interior trim e.g. architraves, skirtings|
|Western red cedar||Low density softwood, straight grain, coarse texture, good dimensional stability, weathers to silver-grey colour, dry sapwood susceptible to borer attack||Exterior joinery, weatherboards, interior finishing, window opening sashes|
|Redwood||Moderately durable above ground||Weatherboards, window opening sashes|
|Pinus radiata||Moderately durable above ground, requires treatment||General framing (boric treated), doors and windows, interior finishing (finishing grade)
|European larch||Moderately durable above ground, difficult to treat||General framing, interior finishing|
|Corsican pine||Moderately durable||General framing|
Native timbers were not generally treated. In cases where treatment was required, timber was painted with creosote, a preservative made from coal tar, but this had only limited application and use.
Boric treatment was introduced in 1952 to treat timber for internal use. It provides resistance to borer attack (see borer) and provides a degree of fungal resistance. It is an odourless treatment that has low toxicity and no known skin irritability or respiratory problems associated with it. It is also a flame retardant.
Copper chrome arsenate (CCA) treatment (trademarked as ‘tanalised’) was developed in the 1930s and introduced into New Zealand in 1955 to treat timbers for external use. It was initially only used for fencing and poles. Compounds in CCA preservative are toxic to people, with arsenic a known carcinogenic (see Health risks – treated timber for advice on using CCA-treated timber safely).