Building a Dry Stone Wall: Key Principles

Why Dry Stone Walls Still Matter

Walk almost anywhere in the uplands of Yorkshire, the Cotswolds, the Peak District or the Scottish Borders and you will find them: ribbons of grey and honey-coloured stone stitched across the landscape, holding sheep in and weather out. Dry stone walls have been part of British farming for centuries, and a well-built one will outlast the person who built it by a hundred years or more. The reason is simple. Instead of relying on mortar to glue the stones together, a dry stone wall relies on gravity, friction and careful selection of the right stone in the right place. Get those three things right and the wall becomes a single, flexible structure that shifts with frost and settles with the ground rather than cracking apart.

If you are thinking of tackling a stretch of wall on your smallholding, or repairing one that has slumped, the principles are not difficult to grasp. They are, however, unforgiving. A wall built in a hurry will lean, bulge and eventually collapse.

Start With the Footing

Everything depends on the footing. Dig a shallow trench slightly wider than the base of the wall you intend to build, and bed it with the largest, flattest stones you have. These foundation stones should be set well below ground level, at least a few inches, so that frost cannot lift them and so that the weight of the wall above pushes straight down into undisturbed soil rather than into loose backfill.

The footing stones should be laid flat, broad face down, and packed tightly together. Any gaps between them get filled with smaller chippings, sometimes called hearting or pinning, tapped in firmly with a hammer. This is the first place where beginners go wrong. It is tempting to leave voids at the base, but every hollow becomes a place where the wall above will eventually sag.

• Dig down to firm, undisturbed ground, not just to the topsoil.
• Use your biggest and flattest stones for the base course.
• Set the foundation stones slightly wider than the wall above.
• Pack every gap with small stones before moving up a course.

Two Faces, One Wall

A traditional dry stone wall is not a single thickness of stone. It is really two walls built side by side, leaning very slightly inward towards each other, with a core of smaller rubble between them. Each face is built with its stones laid lengthways into the wall, so that the long axis runs across the thickness rather than along it. This is called laying stones "on the bed" and it is what gives the wall its strength.

As you build upwards, the wall should taper gently. A base perhaps 600mm wide might narrow to 350mm or so at the top. That taper is structural, not decorative. It lowers the centre of gravity and makes the whole thing far more stable. Keep the courses roughly level, but do not fuss over perfect horizontality; a little natural waviness is part of the charm. What matters is that each stone sits solidly on the one below, with no rocking.

Through Stones and Hearting

About every metre along the wall, and at least once in every course, you should place a through stone – a long stone that spans the full width of the wall from face to face. These are the ties that bind the two halves together, preventing them from splaying apart under the weight of the hearting and the pressure of frost. Without through stones, a wall may look sound for a decade and then peel open like a book.

The hearting – the small stones wedged into the middle – is just as important. It does two jobs. First, it fills the void so that the faces cannot move inward. Second, its weight adds mass to the wall, which helps it resist wind and impact. Good wallers keep a bucket of small stones beside them and never leave a hollow space. Tap each piece in with the hammer so it locks tight. Loose hearting is nearly as bad as none at all.

Coping: The Wall's Own Roof

The top of the wall needs a roof. This is the coping, and on most traditional walls it takes the form of a row of stones set on edge, leaning slightly, often called cock and hen coping. Each pair of stones leans against its neighbour, forming a shallow tent shape that sheds rainwater away from the wall's core.

This matters more than many people realise. Water is the enemy of a dry stone wall: it freezes, expands and prises stones apart. A good coping keeps the heart of the wall dry, and it also caps the structure so that the top courses cannot be dislodged. Coping stones are usually the largest, heaviest and most carefully chosen stones in the wall, and they should be set so that they overlap the faces below by a small amount, giving the wall a slight overhang and a clean, finished line.

Why No Mortar Is Needed

Mortar seems like the obvious answer to keeping stones together, but on a field wall it does more harm than good. A rigid, cemented joint cannot move. When the ground shifts with frost heave, when a sheep leans against the wall, or when water gets behind the render and freezes, a mortared wall cracks. Once cracked, water penetrates and the damage accelerates.

A dry stone wall, by contrast, has thousands of tiny moving joints. It flexes, settles and drains. Rain runs straight through it rather than pooling behind it. That is why a wall built without mortar can stand for 150 years with only occasional repairs, while a mortared one may need rebuilding in thirty.

The craft is old, and it rewards patience. Take your time over the footing, keep the faces tied with through stones, pack the hearting tight, and finish with a proper coping. Do that, and you will have built something that belongs in the landscape – and that will still be standing long after you have hung up your hammer.