Repairing dry stone walls around a country garden

Why a dry stone wall deserves a proper repair

A dry stone wall is the quiet backbone of a country garden. It holds a slope in place, shelters a border from the prevailing wind, and gives somewhere for ferns, stonecrops and the odd slow worm to make a home. Built well, it will stand for a century or more without a drop of mortar. But even the best wall loses a stone here and there, and once a gap appears the trouble can spread quickly. A missing stone lets the ones above it shift, and a shifted wall sheds its coping and starts to bulge.

The good news is that dry stone is one of the most forgiving things you can repair yourself. There is no cement to match, no curing time, and you can stop for a cup of tea halfway through without ruining the job. The trick is to work with the wall's logic rather than against it.

Gathering the right stone

The single most important decision is the stone itself. Match the existing wall as closely as you can. In much of the UK that means limestone in the Cotswolds and the Peak, sandstone in the Welsh borders and parts of Yorkshire, granite in the south-west and Scotland, and slate or shale in the Lake District and mid Wales. A wall of pale limestone patched with red brick or grey concrete will stick out like a sore thumb for the next fifty years.

Where can you find suitable stone?

• Ask a local farmer or landowner — most have a corner of a field with an old collapsed wall or a pile of field stone.
• Reclaimed stone yards often stock walling stone by the tonne, though it is not cheap.
• Newly quarried stone is available for many traditional types, and it will weather in within a season or two.
• Your own garden may have a buried cache — old gateposts, foundations, or a heap behind the shed.

Set aside stones in three sizes before you start: large foundation stones, medium walling, and thinner flat pieces for the hearting and the top courses. Sort them into rough piles so you are not hunting when your hands are covered in grit.

Tools and a safe working method

You need surprisingly little. A pair of sturdy gloves, a lump hammer, a cold chisel for dressing awkward stones, a spirit level, a builder's line, and a decent bar for levering. A rubber mallet is gentler than a metal hammer when you are tapping stones into place.

Before touching anything, stand back and look at the wall. Photograph it. Note how the stones are laid — in most traditional walls they run lengthways into the wall, not along it, so the face you see is the end of each stone. This is what gives a dry stone wall its strength and its characteristic look.

Work in short sections, no more than a metre at a time, and never remove more than you can comfortably rebuild in a single session. If the wall is leaning, take it down to sound stone and rebuild from there. If it is only a hole, you can often key new stones into the existing fabric.

Building the base and the body of the wall

Dig out the gap to firm ground and lay a course of the largest stones flat, wide side down. This foundation course should be at least as wide as the wall is thick, and ideally a little wider — it carries everything above it. Bed each stone firmly, tapping it down with the mallet until it rocks no more.

Now comes the rule that separates a wall that lasts from one that slumps: keep the base narrow. Actually, keep it wide at the bottom and taper it as you rise. A well-built wall is roughly twice as wide at its foot as at its top, giving it what wallers call batter. A wall with parallel sides has nothing to lean on and will bulge.

Build up in courses, placing each stone so it bridges the joint below rather than sitting directly on top of it. Fill the middle of the wall with hearting — small chips and flakes jammed in tightly — because this is what stops the two faces from moving independently. Tap the hearting home with the hammer. The wall should feel solid under your hand at every course.

Keep checking with the line and the level. A slight lean into the bank is fine and often desirable; a lean out into the garden is a slow-motion collapse waiting to happen.

Coping stones: the crown of the job

The coping is the row of stones on top that sheds water and locks the whole structure together. Traditionally these are set on edge, slightly tilted, and arranged so each one overlaps its neighbour. On some walls they are placed vertically, like a row of books; on others they sit flat but angled.

Whatever the local style, the principles are the same. Choose the flattest, most regular stones for the coping. Bed them on a firm course of smaller stones, not on loose hearting. Place them so the joint between two coping stones sits over the middle of a stone below, never over a joint. Give each a gentle tilt so water runs off, and pack the gap behind with small stones so nothing shifts.

If the wall has a slight curve or a corner, take extra care here. Corners take the most strain, and a coping stone that is not bedded properly will work loose within a winter.

Finishing, planting and the long view

Once the repair is complete, brush the face down with a stiff brush and step back. A good repair should look slightly new for a season and then disappear as lichen and moss move in. If you have had to rebuild a long section, resist the urge to point it with mortar — that traps water and defeats the whole purpose.

Plant into the base if you like: alpine strawberries, aubrieta, wall pennywort and ferns all enjoy the cool, free-draining root run. Keep ivy and larger shrubs away, as their roots will prise the stones apart.

Finally, keep an eye on the wall through the year. A stone knocked out by a dog or a delivery van takes five minutes to replace. Left until spring, it can mean a metre of coping on the ground. Dry stone rewards attention, and a wall you have repaired yourself becomes part of the garden in a way that nothing bought ever quite does.