Dry Stone Walling Basics for Garden Boundaries

Why a dry stone wall belongs on a smallholding

A dry stone wall is one of the few boundaries that gets better as it ages. It needs no mortar, no footings of concrete and no annual painting, and when a section slumps after a hard winter you can lift it apart and rebuild it in an afternoon. For a smallholding it also does quiet work that a fence cannot: it slows the wind, holds warmth in the soil behind it, and offers thousands of small voids where insects, amphibians and small mammals shelter.

For a garden boundary, aim for a finished height of about 1 metre, and no more than 1.2 metres unless you have built a few before. A wall at that height is comfortable to build, easy to repair and heavy enough to stay put. Anything taller needs thicker through stones, more skill and a good deal more stone.

Choosing and sorting your stone

Almost any local stone will work if it splits into flatish, blocky pieces. Limestone, sandstone, gritstone and slate all dress well and are forgiving to shape. Granite is tougher going but lasts forever. What you want to avoid is anything rounded — sea-rounded cobbles, river pebbles and smooth field boulders simply roll out of a wall the moment it settles. Broken concrete and old brick are best left out too; they crumble and look wrong beside natural stone.

Before you lay a single stone, sort your pile into three groups:

• Face stones — flat, roughly rectangular, with at least one good face and two reasonably parallel beds.
• Hearting — small chips and wedge-shaped offcuts, ideally no bigger than your fist.
• Throughs and coping — long, heavy, flat stones that will span the wall and top it off.

You will need more hearting than you think. As a rough guide, allow about one tonne of stone for every square metre of finished wall face, so a 10-metre boundary at a metre high is around ten tonnes of material. Useful kit: a 4lb lump hammer, a stone punch, thick gloves, safety glasses, a string line, a spirit level and a pair of wooden profile boards cut to your wall's batter.

Getting the foundation right

Dig a trench 150–200mm deep, or 250–300mm on heavy clay, and slightly wider than the wall's base. Dry stone walls are wider at the bottom than the top, tapering inwards on both faces. A good rule of thumb is that the base should be roughly half the height of the wall, so a 1.2-metre wall starts at about 600mm wide and finishes at 300–350mm. The taper, or batter, should be about 50mm of lean for every 300mm of height on each face — roughly 1 in 6.

Rake the trench bottom flat, ram it firm, and bed in a layer of compacted hardcore or packed small stones. Then set your first course: the largest, flattest stones you have, laid flat with their long axis running across the wall rather than along it. Every stone should sit solidly with no rock or see-saw. Run a string line along each face and check your profile boards at both ends before you go any higher — a wall that starts twisted stays twisted.

Building the courses

From here the principle is simple: you are building two faces and one heart, all at the same time. Work up both faces together, never one side then the other, and keep the courses roughly level as you go.

• Each stone should sit on a flat bed, span two stones below it, and bridge the joint beneath — never allow four joints to meet at a single point.
• Tilt every face stone very slightly into the wall so rainwater runs off rather than sitting on the bed.
• Fill the middle with hearting as you rise, wedging it tight with the hammer. Packed hearting is what stops the faces spreading.
• Set through stones — long stones running the full width — every 1 to 1.5 metres along the wall, and at both ends. On a wall over a metre high, use two rows: one about 300mm up and one roughly 300mm below the top.
• Build the ends as a neat stack of the biggest, flattest stones you can find, laid as throughs so the wall ties together at the cheek.

Coping, finishing and living gaps

The coping is what sheds water off the wall and holds everything beneath it down. Either set large flat stones on edge in a tight row — the old "cock and hen" finish — or lay a course of heavy flat stones across the top, overhanging each face by 20–30mm so drips fall clear of the stonework. Both work well; the on-edge style needs more stone, the flat style is quicker.

Build in spring or early autumn, when the ground is workable and the stone is dry. Frost-heave and numb fingers make late November thoroughly miserable.

Finally, resist the urge to point the wall with mortar or cement. Mortar traps water, cracks in frost and kills off the very habitat that makes a dry stone wall worth having. Leave the base slightly open, keep a few deliberate gaps in the hearting, and you will soon find toads, newts, slow worms, voles and solitary bees moving in, with mosses and lichens following on the faces. After a hard winter, walk the wall, lift any slipped coping back into place and rebuild the odd collapsed section while it is still small. Keep strimmers and ivy away from the faces, and it will stand for a lifetime.