Dry Stone Walls

Dry-stone walls

If you want to build yourself a house in the city, brick, steel, glass, and wood are generally the best materials to use. But what if you're in the middle of the countryside and you want to make a simple wall to keep animals in a field? You could use bricks, but they look unattractive and unnatural in rural landscapes. Not only that, they can work out really expensive when you lay them mile after mile. And what if you change your mind about where you want the wall to be, as farmers often do? Knocking down bricks locked together with mortar isn't at all easy. Wouldn't it be good if there were a simpler kind of wall you could make? Well, there is! It's called a dry-stone wall because, unlike a brick wall, it's made by stacking stones without (wet) mortar to hold them together. Dry-stone walls are strong and attractive and can last hundreds of years. But if you decide you don't like them, you can just take them down and build them up again somewhere else. Let's take a closer look at how they work!

What's the difference between brick walls and dry stone walls?

A brick wall is made from regular stacks of identically shaped blocks locked together with a kind of gritty adhesive called mortar. A dry-stone wall is much more natural: it's little more than a vertical stack of stones laid together slowly and carefully so they lock together under their own weight. Brick walls need mortar to hold them up because they often reach high in the air (as part of a building, for example). Dry-stone walls, on the other hand, are used mainly for fencing in animals or marking out the edges of a garden, so they seldom need to go higher than 1–1.5 meters (3.5–5 ft). By choosing the stones carefully and packing them tightly together with very thoughtful design, you can make a really strong structure that's completely self-supporting. Apart from looking great, it will provide excellent shelter for livestock and habitats for rock plants (such as mosses and lichens) and the insects they support.

How to build a dry-stone wall

To make a dry-stone wall, you first clear and level the ground to prepare the foundations. Then you sort out your stones into different sizes, typically with piles of large, medium, and small stones. Next you mark out the area where you'll be building your wall—with taut lines of string, by drawing chalk lines on the ground, using wooden stakes, or in some other way. Your wall can be no wider than the longest stones you have, so you'll need to check your pile of material to see what's available before marking out.

Once you've marked the area for your wall, you simply pile the stones up in flat layers. Each layer consists of tightly packed stones with a mixture of a few large stones (called tie-stones) running lengthwise into the wall (that is, with their longest edge spanning the width of the wall) and lots more smaller stones packed in between them. You need to leave as few gaps as possible, so the stones in each layer should look almost as tightly interconnected as jigsaw pieces when you're laying them out. Take time to choose and place your stones carefully: dry-stone walls take a very long time to build, if you do it properly, and it's time that's well spent.

Much like building a brick wall, you finish off a substantial part of each horizontal layer before moving up to the next one. To keep your wall sturdy, it's important to arrange large stones in one layer so they bridge the gaps in the layer below, and vice-versa. Sometimes this is referred to as building "two over one and one over two": you need to make sure one stone covers two (or two stones cover one) in the layer below. In other words, you have to ensure that the gaps in successive layers don't line up or you'll create "faultlines" where your wall will be much more likely to collapse. Another important factor also helps to ensure stability: the lower layers of a wall are always slightly wider than the upper ones so the wall tapers inward slightly as it rises. If your wall gets wider as you go up, there's something wrong!

When you reach the height you want, you can put more flat and heavy stones on top to finish the wall off. Usually, wall-builders arrange flat stones on their ends along the top both to give a wall an attractive finished appearance and to stop the top stones falling or being knocked away. The upper stones are referred to as the capstones or topstones, "buck and doe," or "cock and hen." Usually, different craftsmen have their own individual ways of topping a wall; it's very much a matter of personal style and preference.

Local materials and styles

One of the best things about dry-stone walls is that they're usually built from local stones. Using materials made locally is better for the environment (energy isn't wasted transporting heavy building materials over long distances). It also helps places to retain their distinctive character and charm. Dry-stone walls built in one place may look very different from those built elsewhere, simply because the stones are a different shape, size, or color. In some places, the natural stones are like small cobbles and dry-stone walls reflect this. Elsewhere, the stones may be chipped from rocks in local quarries to make bigger and squarer pieces.

Different wallers build in different styles—sometimes to "sign" their work and sometimes for other reasons. Walls built up hills often use a style where the stones are packed in at angles so their weight (leaning against the direction of the incline) prevents the structure from collapsing. Walls designed for livestock often have a protruding layer of stones near the top that helps to stop sheep or deer from jumping over. In the part of Dorset, England where I live, the wallers say they can recognize one another's style at a glance. You can certainly see a huge variety in walling styles as you walk around the landscape comparing one wall to another. Something else that's very evident is the sense that dry-stone walls are a living feature of the landscape: for one reason or another (through ground movement, strong winds and rain, or livestock huddling against them for shelter), walls collapse from time to time and have to be rebuilt. Look closely at the walls in a particular area and you'll find places where stones that have been in place for hundreds of years are just about to fall down; right next to them, you'll find stones that have been built up again in the last few days, weeks, months, or even years. It's as though the walls themselves are alive, constantly renewing themselves. It's fascinating stuff! We should count ourselves very lucky that people keep these traditional rural crafts going.

Advantages and disadvantages

Pros

Visually attractive, hand-made appearance.
Help to perpetuate traditional crafts.
Reflect local character with local materials and better for the environment (need no transportation).
Excellent habitat for mosses, lichens, and the wider ecosystem.
Relatively easy to move or remove.
Can be recycled and reused any number of times, very easily.
Last forever (in theory). Unlike with a brick wall, there's no mortar to crack and fall apart.

Cons

Slow, laborious, and expensive to build (particularly because of high labor cost).
Tend to collapse if poorly built.
Difficult to build if you don't have a ready supply of stone nearby.
Unsuitable for high walls or buildings.
Relatively wide, with a bigger land-take than a simple barbed-wire fence or brick wall, though not as wide as a hedge.

Source : http://www.explainthatstuff.com