Story: Building materials
Wood was an obvious choice of building material in a country covered in forest – even in the early 2000s it was ubiquitous, using New Zealand’s exotic pine forests. Many houses were topped off with iconic corrugated-iron roofs. But concrete, aluminium and plastic are ousting traditional materials.
Full story by Jeremy Salmond
Main image: Concrete block wall
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Māori used what they found in forests and swamps to make houses and other structures. When European settlers first arrived in Wellington, Māori helped them make shelters of wood, reed, grass and bark.
Early arrivals from Britain made houses as they had back home, out of clay mixed with straw or grass, layered to form thick walls. These were called cob houses. Sometimes the clay was made into large blocks called adobe. Squares of turf were also used, laid on their sides to form sod houses.
There were large forests, and wood was used on the inside and outside of houses. Roofs made of wooden tiles were draughty and let in the rain. Inside walls were large planks of wood covered in woven fabric called scrim, and then with wallpaper.
Before steam-powered saws, people cut wood using pit saws – one man stood on a felled tree working with another man in a pit dug under the tree. After the 1850s timber was mostly milled by machines. Because nails were so expensive, ‘trunnels’ or treenails were used – wooden pegs which secured joints.
Timber and plaster board
Timber from pine forests is tanalised to make it last longer, using copper, chrome and arsenic mixed in water. Timber sizes changed when metric measurement was introduced. The classic New Zealand ‘four-by-two’ (100 by 50 millimetres) is now a smaller 90 by 45 millimetres.
Timber is glued together to make products like plywood, chipboard and MDF (medium-density fibre board). A plasterboard called Gibraltar board became the most common material for internal walls in the 20th century.
Stone, bricks and mortar
Brick making was common from the 19th century, but brick or stone buildings did not withstand earthquakes well. So instead people built houses from timber and used bricks as a veneer. Until the 1950s most houses had chimneys made from bricks.
High-quality Portland cement made in Warkworth began to replace imported cement after 1883.
Moulded concrete blocks are hollow in the middle. They are made into walls with steel reinforcing running through them. Blocks are joined together with a layer of mortar. Concrete blocks are popular in New Zealand because they speed up construction. People also use concrete precast in moulds in a factory and then assembled on site.
Concrete is also used in terrazzo, coloured concrete which is highly polished and used for floors or benches, and Konka board, concrete made with pumice and backed with paper.
Concrete products made with asbestos were popular until people realised asbestos causes asbestosis, a deadly lung disease.
Steel, aluminium, plastics and insulation
Buildings made with steel frames are strong. They can be tall and they resist earthquakes. Aluminium has almost completely replaced wood in window frames and joinery. Plastic is also widely used, particularly in plumbing. Insulation comes in many forms, including fibrous blankets, some made with wool.
Roofing and glazing
Corrugated iron was widely used for roofs. It was first imported in 1843. To stop the steel rusting, it was coated with molten zinc. Lead-capped nails kept the roof on. From the 1980s corrugated iron was replaced by products like Zincalume, aluminium-coated steel.
Slate roofs were not common, but concrete and terracotta tiles were popular.
Glass has always been imported. At first people bought small pieces – if one pane in a window broke it did not cost too much to replace. In the early 20th century stained-glass leadlight windows were popular – small pieces of coloured glass moulded together with lead.
Nails, screws and bolts are all used in construction and are mostly imported. In the early 2000s builders used compressed-air-powered nail guns.