Stone
Stone or brick were the most common building materials in Britain in the mid-1800s. Loose stones were used as they were (described as ‘rubble’ construction), or were roughly squared to fit against each other. In better-quality buildings, stone from quarries was precisely squared and laid in neat courses – known as ashlar construction.
In New Zealand stone was preferred for important public buildings. Some buildings had corners, window and door openings formed in cut stones, while walls were concrete. Local and imported stone was used in construction of buildings in the 19th century, but it is not a common building material.
Brick
Bricks were made wherever there was clay and sufficient supplies of wood or coal for the kiln. Brick making began very early in New Zealand. Early bricks were hand-made and fired in clamp kilns – a great stack of bricks with firewood between the brick layers. As towns developed, permanent kilns were constructed. Eventually every district had its own local kiln.
Brick and stone withstood fire but not earthquakes. So a technique called brick-veneer construction developed with an exterior wall of brick attached to a timber frame. The most common use of brick in houses was in chimneys. Right through to the 1950s it was customary to have fireplaces in main living rooms and kitchens, and often in bedrooms.
Early plaster
Lime was a key component of many interior finishes. The European practice of solid plastering was common in New Zealand in brick and stone buildings. Solid plaster was a very smooth finish formed in three layers, beginning with a lime plaster ‘scratch’ coat, a second ‘bond’ coat, and a final ‘skim’ coat of gypsum plaster.
Making lime
Lime was the critical ingredient of mortar used in masonry construction, particularly for making brick chimneys. Limestone (or some other form of calcium carbonate) was burnt in a special kiln to form quicklime. Quicklime was mixed with water (known as slaking), resulting in lime putty, a thick creamy mixture. This was mixed with sand to make mortar, which hardens due to a chemical process called carbonation. As water evaporates, the lime reacts with carbon dioxide in the air, undergoing a chemical change which turns it back into calcium carbonate.
Another type of lime – hydraulic lime – sets partly in a reaction with water. Experiments with this, which began in the 1700s, eventually led to the development of Portland cement. This forms the basis of modern concrete, a much harder and stronger material. Cement was imported from England as early as 1843, and numerous concrete structures were built between 1840 and 1900.
Warkworth’s Wilson brothers produced New Zealand’s first Portland cement in 1883, and by the late 1890s Portland cement manufacturing was well established and competing with imported cement. By 1892 a third of all cement used in public works was locally made, and by 1920 almost all cement was locally produced.
