Portfolio > Drystone walls
In our design work, the nature of materials is very important to us. Even artificial materials, such as concrete or brick, impart their own particular character. Amongst the construction materials with which we work, stone is perhaps the most varied and interesting. Basalt, scoria, limestone, greywacke, argillite, ignimbrite or andesite; they all bear their own characteristics, and demand differing treatments.
Stone has a dynamic, organic complexity to its composition; the character of which regularly tells the story of the (often powerful) natural processes which formed the stone. This results in surfaces which are like complete 'miniature landscapes'.
Truth to the nature of the material is an important aspect of good drystone walling. Utilising local stone should therefore be the starting point not just for selecting material, but also the style of construction that will be employed in a wall.
An important term to be familiar with in relation to drystone walls is the description of a wall as being 'coursed' or 'uncoursed'. Put simply, 'coursed' means that the wall is roughly formed of rows of stones, similar to a brick wall; whilst an 'uncoursed' wall does not ascend in distinct rows. Whether a wall is coursed or uncoursed, the fundamental principles are the same, and the more regular appearance of a rigidly coursed wall does not necessarily make it more stable than an uncoursed wall. Generally speaking, the stones within a wall should decrease in size, as one looks further up the wall (both for structural and aesthetic reasons).
Walls that we have made in greywacke and andesite have been built in an undulating, coursed arrangement (as would walls constructed from limestone), whilst our basalt/scoria walls have more uncoursed compositions. This reflects the nature of the respective stone with which we are working at any time.
Process
Drystone walls are self-stable. They most commonly consist of two sides, and a core of smaller stones and offcuts (known as corefill) - although single-stacked stone walls (involving tremendous skill) are traditional to parts of Britain and Ireland. Gravity directs the load straight down, whilst the inwardly sloping faces of the wall also direct the load towards the centre of the wall.
The base stones are especially large, and the contrast between them and the smaller stones used on the upper courses contributes substantially to the character of a wall. The base layer of a wall is actually a very beautiful entity in itself, due to the dynamic combination of the straight outer edges, undulating inner edge of base stones, and the smaller corefill stones.
As logic dictates, the wall is then gradually lifted, with the core filled tightly as one works upwards. Profiles are established early, to ensure that an appropriate batter is maintained - typically, a 1m high wall may taper from 600mm wide at the base to be 250mm wide at the top.
At various points within the wall, 'throughstones' should be placed. These stones span the full width of the wall, and strengthen it greatly by binding both faces. The final part of the process is the application of capstones, which must be heavy enough to sit solidly upon the penultimate course of stones. Capstones are placed in direct contact with each other and, if well placed, form a remarkably tight chain (whose strength lies in the combined friction between themselves, and the stones beneath them).
Influences upon our drystone walls
O2 Landscapes' interest in this art perhaps stems partially from the fact that I grew up in the middle of an old quarry (on one of the Three Kings within Auckland). When we were young, my father constructed a stone wall at the back of the property, which still stands in perfect condition. 
As I became increasingly interested in gardens, the part of the wider landscape that resonated most with me was the humble fabric of many older parts of Auckland, which had often been constructed simultaneously with a great degree of naivety and innovation. They had also been permitted the dignity of being allowed to age, a concession that we make less and less with the continual reinvention of landscape spaces.
Amongst the features of such landscapes, drystone walls are especially appealing, as they are the epitome of an indigenous form; local material assembled in local methods, in a manner that is intrinsically suited to the nature of the material. In addition to working extensively with drystone as a medium, I have observed traditional walling within and outside the Auckland area, both in New Zealand and abroad. Notable areas which have been instructional to our work include the Otuataua stonefields in Mangere (which are of historical significance on account of both their pre-European Māori and early European settlement), the very well-built walls surrounding the Whangarei area (especially those of Glenbervie), and drystone walls and 'Cornish hedges' within the areas surrounding Penzance in Cornwall (including the ancient walled fields of Zennor).