building history The rise of pine Relative newcomer Pinus radiata quickly established itself as a worthy substitute for diminishing native timber resources, but not without first overcoming preservation issues. By Nigel Isaacs, BRANZ Principal Scientist and Teaching/Research Fellow, School of Architecture, Victoria University of Wellington

nce New Zealand had started down was followed by an expansion of state exotic mill were built of pine produced by the nearby the path of timber buildings, the slow- afforestation in the decade to 1935. Waotu sawmill. An early resident remembers growing native timbers were rapidly From the late 1920s private commercial the weekly weighing of a floorboard to O consumed. By the 1950s, only nine interests actively sought finance to plant forests, determine how much moisture it had absorbed. native tree species were used to any extent: often through the issue of private company A preservation plant was also set up based on ❚❚ Softwoods – kauri, rimu, matai, totara, bonds – a practice that accelerated out of two pressure cylinders obtained from a defunct kahikatea and miro. control until the Bondholders Incorporation Act concrete block plant in South Auckland and a ❚❚ Hardwoods – tawa, red and silver beech. 1934­–5 brought order to the chaos. One of boiler from a sawmill in Tauranga. Although The dwindling supplies of native timber were the companies to emerge from this was New built to last only 10 years, the Pinedale sawmill replaced by a relative newcomer – the exotic Zealand Forest Products Ltd. continued to be used into the 1980s. Pinus radiata. By the late 1950s, it had become In 1939, Pinedale was established (about It soon became obvious that uses had to be ‘second only to rimu in commercial importance’. 6 km from Putaruru on the railway line to found for the rapidly maturing trees. Sawmills Rotorua) when the village and sawmill were built were established to turn exotic wood into Growth driven by high returns to process the 1,214 ha Pinedale block, which timber, but more processing was required The Forest Branch of the Lands and Survey had been planted by Afforestation Limited from to add value. Opportunities for timber Department had established exotic plantations 1924. In 1941, NZ Forest Products took over the treatment, paper, pulp and timber-based near Whangarei as early as 1890, and from site, setting up a second sawmill. products were explored. 1897 they had begun experimental tree-planting in the Rotorua district and the ‘barren pumice Experimenting with pine for houses From air drying to the kiln region’ of the Kaingaroa plains. The rapid growth Pinedale provided pine for many uses during Although described as ‘soft, light, nails well, of Pinus radiata was recognised by 1909 as World War II – the exotic timber previously used fairly tough and strong, clean and straight if providing an attractive commercial proposition. for butter boxes proved it could substitute for the well grown’, the principal limitation of Pinus By 1923, the State Forest Service estimated the diminishing native timber resources. Pinedale radiata was well understood. The Technical return from radiata pine to be between £250 provided an ideal place to test the performance Correspondence School’s 1958 book Carpentry and £500 per acre. The promise of such returns of Pinus radiata in housing, as the houses and in New Zealand, for example, modestly

Pinedale circa 1947, surrounded by the cut-over forest. On the right is the settlement with the married men’s houses, towards the centre the single men’s huts and cookhouse, to the left on a hillock stands the manager’s house. (Photo courtesy Mrs Buckett.)

98 BUILD 115 December 2009/January 2010 reported that ‘preservative treatment was A range of processes to force the preservatives Value-added wood-based products required where any likelihood of dampness’. into the timber were also developed, The processing from log to timber produces waste Dry timber is the first step to preservation. Air many tracing back to the Bethell pressure – notably bark and sawdust. While these can be drying, or ‘seasoning’, has a very long tradition, impregnation process, which was patented in burnt to produce steam to drive the machinery, for it not only lightens the weight but also offers 1838. Pressure-based processes are designed other products may be more valuable, such as dimensional and structural stability (reducing to ensure the entire piece of timber is protected fibreboard, hardboard, softboard, particleboard, warping and shrinkage). The timber is carefully by the preservative, but require a specialist plywood and laminated veneer. These can be stacked above the ground, with each board being pressurised treating cylinder. Other processes made from wood waste (scraps, sawdust) or separated from its neighbour by spacing timber. include dipping in a cold preservative fluid, purpose-made wood chips, strands, fibres or The moving air and sun work together to dry out diffusion where the warm timber is placed in veneers, but other non-wood fibres such as the timber, but the process requires considerable a cold preservative bath (or vice versa) and hemp, flax, jute or straw can also be used. land and time to create the desired result. brushing or spraying the preservative directly Some products such as hardboard and From the 1870s, kiln drying provided the onto the timber. softboard are formed by little more than heat same benefits plus improved uniformity of and pressure bonding the specifically prepared drying. It also required less land and time, Codes in 1950s detail use timber fibres together. Other products require therefore providing greater profit. Kiln drying Faced with fast reducing supplies of native timbers the use of specialist resins, often combined with can use different fuels such as wood, oil, natural and the increasing availability of the largely heat and pressure. gas, geothermal steam and even the modern unknown Pinus radiata, the building industry Investigations in America and Australia into technology of heat pumps. needed knowledge and a degree of certainty. the use of New Zealand grown Pinus radiata for How should this timber be used and what, if any, paper production eventually led to the establish­ Preservation practices over time preservative treatment was required? ment of Whakatane Paper Mills Ltd, which Chemical-based wood preservation has a very It took until February 1953 for the release undertook the first commercial pulping ofPinus long history. Salt was used in ancient times as of two critical New Zealand standard codes radiata in 1939. Nowadays, a range of papers a preservative for ship timbers while wood for of practice – CP2 Use in building of Pinus are produced, as well as pulp for export. buildings was sometimes charred to prevent rot. radiata and other pinus species and CP4 In the 1830s, a method was patented in Britain Timber preservation. CP2 provided guidance Production today for treating wood by ‘dead oil of tar’ or creosote as to treatment, grading and use of pine in The forestry industry, today largely based – one of the many byproducts of the town gas light timber-framed buildings. CP4 combined around Pinus radiata, has continued to grow. industry’s use of coal. South African, British and American standards According to the Ministry of Agriculture and Many other preservatives were also developed with New Zealand research and experience to Forestry’s 2009 Forestry Sector Study, New from the 1830s onwards, including waterborne establish a suitable treatment to protect pine Zealand’s timber resources currently support mercuric chloride (1832), solvent-soluble against insect attack and fungi growth. around 370 sawmills, seven pulp and paper copper naphthenate (1889) and water-soluble In 1956, CP2 use of pine was incorporated mills, three medium-density fibreboard (MDF) boron treatments (1950s). In recent years, in the Standard Code of Building By-laws mills, three particleboard mills, six plywood solvent-based light organic solvent preservative Part IX – Light timber construction (NZSS 95), and laminated veneer lumber plants and about (LOSP) treatments have been used. the ancestor of the modern NZS 3604. 80 remanufacturing plants.

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