Quarrying & Mining Magazine
Q&M

Spare rocks make great walls

This article first appeared in Q&M‘s December-January issue.

Not all quarry stones are crushed into aggregates and there has been a trend in recent years to build drystone walls in the style of rural landscapes of past centuries. Drystone wall builder and Q&M contributor 
PETER OWENS explains.

The early Scottish settlers in the lower South Island built drystone walls to form paddocks to confine stock. This was because timber was scarce and expensive to buy when it was available, and surface stones were aplenty and free of charge both on Crown land and on the land of wealthier settlers who could afford wooden fences on their properties. Drystone walls were also sturdy and didn’t need expensive mortar.

Each course of stones bridges the join between the stones beneath it, creating a stable wall, spreading the load. The stones slop slightly outwards, allowing rain water to run out of, not into, the wall.
Each course of stones bridges the join between the stones beneath it, creating a stable wall, spreading the load. The stones slop slightly outwards, allowing rain water to run out of, not into, the wall.

The drystone walls erected by the pioneer settlers on Otago Peninsula remain today, still serving the purpose for which they were erected. While many southern drystone walls are constructed from Central Otago schist, many types of stones were used.
While there has always been a market for ornamental stones and boulders for the building trade and for larger horticultural operations, there is growing demand for stones and boulders in the construction of modern drystone and similar feature walls on quite small holdings.
Quarries in the region have probably been approached for drywall stones by people who only have a vague notion of what they need.  Kerry Sands of Southern Aggregates says his company has been approached by property owners who want to select and buy their own stones direct from its Greenhills Quarry to bypass the middle man and consult a specialist at the quarry on suitable drywall material.
These modern wall ‘pioneers’ usually have little idea of what is in store for them in terms of the slow, hard work involved erecting a drystone wall, and often give up after a couple of weekends’ work. The blunt truth is – drywalls take time and unremitting toil, but the results are worth it and long-lasting.
So it is not surprising many are willing to pay well for someone to design and build a wall for them. I think this could prove a good business for quarry workers, even if only on an after-work or weekend basis.
After the stones have been supplied and delivered, a drystone wall needs a firm foundation because considerable weight is imposed on it by the finished wall. This is usually achieved by measuring out the length of the wall and digging out to a depth of about 50 centimetres, which is then covered with a thin layer of concrete about five centimetres deep. This covering must be even – requiring use of a spirit level.
The next step is equally important. This is the choice and laying of thick and solid foundation stones for the bottom course. These stones should be the full width of the wall, which should be about 60 centimetres wide. They should also be reasonably flat and laid end to end on the concrete. They must also be closely fitted, and any gaps filled with small stones so that there is a complete course of stone on the concrete.
A dry stone wall is actually two walls, with a rubble fill. It is wider at the bottom, tapering slightly as it goes to the top.
A dry stone wall is actually two walls, with a rubble fill. It is wider at the bottom, tapering slightly as it goes to the top.

Next is the awkward part of the wall construction as stones are chosen to fit in two rows on either side of the base stones. These should be reasonably flat and must fit together as closely as possible. Any gap between the two rows has to be totally filled with small stones as the absence of air makes the drystone wall solid and permanent.
The wall must be built with a slight inclination towards the centre, so when the top has been reached it will require only a single row of stones.
After about three rows of stones have been laid on each side, a tie stone is laid to assist in binding the two sides together. This should be a reasonably flat stone that is the approximate width of the entire wall. Tie stones should be inserted about halfway up the wall at a distance of about one metre.
When choosing stones it is best to select flat and rectangular ones as round ones tend to ‘rock and roll’. The stones must also be laid like a brick wall in that every stone must lie upon two others – again to provide strength. The stones must also be laid in the same way firewood is stacked – with the thin long sides facing into the wall centre and and the short side exposed to the outside.
I assure you – building a drystone wall is slow work and time consuming but, no matter how long it takes, it is essential to regularly check that the wall rises with the necessary inclination. To this end you can make a template from wood and regularly check the inclination of the wall.
When the wall has been erected to a stage when only a single topping of stones is required, some people finish it off with rounded stones or even top it off with soil in which plants can grow.

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