Buildings of stone
Few buildings were constructed of stone in New Zealand and today it is more likely to be used for façade than structure.
From the earliest days of European settlement, stone has not been the most used construction material in New Zealand. In the 1861 Census, only 2% of dwellings were brick or stone (these were counted together), 68% were wood and 16% were canvas. As the country became more urbanised, and the temporary tent buildings of the gold rushes were replaced, timber was favoured because of its ready availability and ease of construction. By 1901, only 4% of dwellings were brick or stone, whereas 90% were timber. Stone was often used in prestigious buildings, such as churches and town halls.
Not all stones good for building
Stone is heavy and durable, and although strong in compression, it is weak in tension, and its earthquake performance is poor without reinforcing. Most rock types are good conductors of heat – for example, the R-value of limestone (0.04 m²°C/W) is only one-tenth the R-value of the same thickness timber at 0.4 m²°C/W. Much heavier rock can store heat from the day and release it in the cool of the night, creating a more comfortable environment.
Not all stones are suitable for use in building. A building stone needs to be readily workable, strong and durable, have a suitable appearance and be fit for purpose. For example, Tonga Bay granite (from Tonga Bay in Abel Tasman National Park) was used for buildings in the 1890s, but it crumbled badly and would not retain a high polish. Today, it can only be seen in the steps built in 1913 leading up to Nelson Cathedral and on the exterior of the 1908 (former) Public Trust Building in central Wellington.
Although decorative stones may be transported long distances, building stones were normally selected from locally available material. Examples include basalt lava in Kerikeri, scoria in Auckland, greywacke in Nelson, marble in Takaka, limestone in Oamaru and schist in Central Otago. Early settlers either used their own skills or the services of skilled masons, if available. The use of local stones resulted in the development of local industries with the skills and expertise for its cutting and construction.
Type of building stones
Building stones are classified by the origin of the rock, and all three types are found in New Zealand:
- Igneous – formed from the cooling and solidifying of molten magma from deep within the earth. This can be hard and strong (for example, granite, basalt, quartz) or, when formed from ash and pumice deposits, more variable like ignimbrite.
- Sedimentary – formed from sediments that accumulated in layers under the sea, lakes or river valleys and were then compacted. These are less durable, and examples include sandstone and limestone.
- Metamorphic – igneous or sedimentary rocks that have been modified by heat, pressure and/or hot gases or solutions. Examples are marble, slate and schist.
Many stones have local or trade names that may disguise or even incorrectly state the type. Among the most well known are Oamaru stone and Hanmer marble (limestone), Halswell stone (basalt) and Hinuera stone (ignimbrite).
Stones’ differing performances led to their use in different situations. Granite, for example, is generally resistant to chemical damage, but a spot of vinegar quickly damages marble.
Two main wall types
Although there are many types of building stone, two main wall types can be used individually or in combination. ‘Ashlar’ uses shaped and formed pieces of stone, whereas ‘rubble’ uses rough stones either as found or further shaped. Although mortar (lime or cement) can be used to both hold the stones together and give shape to the construction, walls can also be laid ‘dry’, with the friction between the stones giving the strength.
The brick and stone front part of Isel House at Stoke, near Nelson, was completed in 1915. The rubble construction used the river stone from nearby Poorman’s Valley, with local bricks used to provide contrast around the windows and corners.
Stone from near and far
Early settlers made use of stones from the land the house was to be built on and nearby fields or rivers. Once transport was available, stone could be brought from further afield, although the cost was limiting for private buildings.
Public buildings were less constrained, and could even attempt to provide regional representation through the materials. The current Parliament House in Wellington, built between 1912 and 1922, replaced the timber structure destroyed by fire in 1907. It is faced with Takaka marble on a base of Coromandel granite.
The marble was extracted from the Kairuru quarry on Takaka Hill using traditional tools and techniques. The photograph shows the ‘plug and feather’ method in use – a development of the even older ‘wedge and groove’ method of quarrying stone. A row of holes was drilled into the marble and a ‘feather’ of two pieces of steel inserted. A ‘plug’ was then driven into each ‘feather’, pushing the two pieces of steel apart, ultimately fracturing the marble and splitting off a large piece that could be further split into suitable sized pieces.
More recently, power tools have revolutionised the extraction of stone. Drills, wire cutters, chainsaw cutters and circular saws permit stone to be more readily and efficiently quarried and then cut to size and shape, to be finished as required.
Oamaru’s Victorian buildings
Around Oamaru, limestone has been quarried since the 1860s. In 1862, the government land sales notice reported that a ‘superior limestone abounds and is generally used for building purposes in the town of Oamaru’. The agricultural wealth of the time supported the construction of substantial Oamaru Stone buildings, many of which form (in the words of the Oamaru Whitestone Civic Trust) ‘New Zealand’s most complete collection of Victorian buildings’.
Façades and many uses
Earthquake and other safety requirements, coupled with the reducing cost of other construction systems (including concrete and steel framing), have meant New Zealand and imported stone is now used more for façade than for structure. Despite this, New Zealand stone can still be found in road curbing, stock or house fences, memorial arches, decorative surfaces in buildings, tombstones, statues, pedestals, plaques, steps, benchtops and roofing slates.
For more
The article benefited from Granite and marble – A guide to building stones in New Zealand by Bruce W. Hayward, published by the Geological Society of New Zealand in 1987.
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Articles are correct at the time of publication but may have since become outdated.
