Story: Roads

Page 3. Building roads

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Choosing routes

Surveyors laid out early roads around hills, to minimise earth moving. Surveyors needed slashers and axes to chop branches that obstructed their line of sight. They used a long coil of wire (a chain), a theodolite (a device on a tripod for measuring angles) and a staff (a long wooden stick with measurements on it, which the surveyor sighted with the theodolite). They laid out new routes and marked them on maps for road builders to follow. Early roadmen sometimes ignored the surveyor’s map, routing roads to allow the sun to dry their surface. Later engineers and surveyors often re-routed roads more directly, through shady gullies or the shadows of hills.

Tools

In the late 1800s the road builder’s first tool was an axe for felling trees, kept razor-sharp with a stone. The second tool was the cross-cut saw, which required two workers to pull it back and forth. Grubbers and picks then cleared the way for shovel and wheelbarrow. From the 1890s gelignite was used to blow up large stumps or rock faces. Single-furrow ploughs, and later double-furrow ploughs and horse-drawn graders, helped to form the road’s surface.

Stony metal

Stones from a riverbed or gravel pit vary in size, and large stones were broken into smaller pieces using hammers. They were then passed over metal screens so those of the same size fell through. These were spread on the roads and called ‘metal’. Unsealed roads are also called dirt or gravel roads.

Road metal

Gangs of men loaded carts with gravel and stones from riverbeds. Sledgehammers and smaller sprawling hammers shattered rocks into metal (small stones of consistent size). It was bone-jarring work. Metal was carted and dumped onto roads, using large round shovels called banjos. Surfacing roads with shattered rock was also known as macadam, after Scottish roading engineer John McAdam who developed the process in the early 1800s.

Road foundations

Road gangs used whatever was available for foundations. In places trees and branches were cut and layered on the road, forming a good base, especially on clay or mud. This was called fascine work. Loads of sand and metal were dumped on top – the branches stopped it all sinking into the clay.

Ideal routes for roads were over flat areas, but they were often swampy. Deep trenches had to be cut for drainage, and the fill from the trenches built up the road surface higher. In some cases the whole causeway slowly sank, and it had to be continually built up.

Mechanisation

By the late 19th century construction was partly mechanised, with the arrival of steam road rollers which gave a much smoother surface. The first roads had been designed primarily for moving stock on the hoof and for light vehicles. As traction engines arrived, rural roads had to be upgraded. Bridges had to be strengthened or rebuilt and roads designed to carry heavier vehicles without breaking up. By the First World War concrete bridges were replacing wooden bridges. Trucks were used increasingly to move stock to freezing works, so even if roads did not receive a great deal of traffic they still had to be well maintained.

Sealing roads

Roading was not just a country problem. City streets were dusty in summer and muddy in winter. At first wooden blocks were used to pave some busy streets in Auckland and Wellington. The process of sealing roads with tar was available by 1900. City streets were the first to be sealed. Dunedin had a machine which tarred streets by 1908. Sealing was very expensive and it was beyond the reach of most local authorities.

Concrete was also trialled as a street surface in the early 1900s, but it proved more expensive than asphalt or tar. By 1929 there were only about 3,000 kilometres of sealed road in the country – less than 3% of the country’s road network. Sealing New Zealand’s road network continued at a gradual pace until the 1950s and 1960s, when it accelerated.

How to cite this page:

Carl Walrond, 'Roads - Building roads', Te Ara - the Encyclopedia of New Zealand, http://www.TeAra.govt.nz/en/roads/page-3 (accessed 15 December 2019)

Story by Carl Walrond, published 11 Mar 2010, updated 1 Mar 2016