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Reading the Wall Before You Touch It

There is something quietly satisfying about a stone wall on a country boundary. It marks the line, shelters stock, gives the wind something to argue with, and holds a whole little ecosystem in its crevices. But before you lift a single stone, spend half an hour walking the length of it with a mug of tea in hand.

Look at how the wall is built. Is it dry stone, laid without mortar, or was it mortared at some point? If it was mortared, you will need to rebuild with a lime mortar mix rather than cement, which traps moisture and will blow the faces off the stone within a few winters. Note the batter, the inward lean of the wall from base to top, usually about one in six. Check the base width and the height. A traditional field wall is often around 600mm wide at the foot, tapering to 450mm at the coping, and standing between 1.2 and 1.5 metres.

Two practical warnings. First, if the wall is on a boundary that appears on your deeds, or sits within a conservation area, or is attached to a listed building, check with your local planning authority before you strip it. Second, and just as important, avoid major work between March and August, when birds, bats and small mammals may be nesting or rearing young. If in doubt, work on a short section and check it over carefully first.

Then plan your campaign. Never drop more than two or three metres at a time, and never take down more than you can comfortably rebuild in a day. A wall left open overnight is a wall that will slump, and stock will walk straight through it.

Sorting the Stone: The Job That Decides Everything

Amateurs rush the rebuild. Professionals spend a surprising amount of time sorting. As you lift each stone, put it in one of five piles, and stack them clear of the wall so you have room to work.

• Face stones: flat, roughly rectangular, with one good straight edge and a sound bedding face. These do the visible work.
• Through stones: long, strong stones that will span the full width of the wall. You need one roughly every metre of length, at two heights.
• Hearting: the small, chunky fragments that fill the middle. This is the mortar of a dry wall, and you cannot have too much of it.
• Coping: the larger, often rounded or angled stones for the top, ideally set on edge.
• Rejects: anything frost-shattered, crumbly or too round to grip. Break it up for hearting, or save it for a drainage sump.

Lay the sorted stone on pallets or on a sheet of tarpaulin beside the wall, keeping the face stones the right way up as far as you can. Knocking the mud and moss off with a stiff brush makes them easier to handle and helps you see the shape. Wear gloves, use a bar to shift the big footings, and lift with your legs. A single coping stone can weigh 25 kilos, and your back will remember every one.

Laying a Firm Foundation

A wall fails from the bottom, almost without exception. Clear the trench to about 300mm wider than the finished wall, then dig down until you meet firm, undisturbed subsoil. Do not build on soft topsoil or on old rubble, however tempting it is on a wet afternoon.

Set your largest, flattest stones as footings, laid across the full width. Bed them down with a heavy mallet or the flat of your hand so they sit solid and level, with their tops slightly proud of ground level. Tilt each footing a fraction so that any water runs outwards rather than sitting in the joint. Set a line up at each end of the section, and stretch a string between them at the base width. Keep checking the level with a spirit level and the line with your eye, because once the faces rise, correcting a wandering wall becomes a miserable job.

Building the Faces and Packing the Heart

Now build two faces, one stone thick, working from both ends towards the middle of the section. The golden rule is one over two, two over one: never let a vertical joint sit directly above another. Lay each face stone on its natural bed, with its longest side running into the wall, not along it, and tilt it very slightly inwards so rain sheds off the face.

After every few stones on each face, fill the middle with hearting. Pack it tight with your fingers and the edge of your hammer; a wall with loose hearting rattles and moves. Bring the two faces up together, course by course, and set your through stones at roughly a third and two-thirds of the final height, spanning the whole width to tie the two faces together.

Leaving Room for Wildlife

A tidy wall is not always a good wall. Leave deliberate gaps, sometimes called mouse holes, at the base every three or four metres, roughly the size of your fist, so hedgehogs, voles, frogs and slow worms can move along the boundary. Keep a few small crevices open in the face rather than filling every joint with hearting, since solitary bees, ladybirds and lizards will use them.

If you have to clear ivy, brambles or grass from the foot of the wall, do it outside the nesting season and never burn the brash against the stone, which spalls the surface. A wall with a little vegetation at the base is a healthier wall than one shaved bare.

Coping, Finishing and the First Winter

Finish with a proper coping. Set the stones on edge, leaning slightly, each one overlapping the next so water runs off the top rather than into the heart. On a curved or sloping run, work downhill so the stones lock against one another. Tap each one down and check that it does not rock.

Stand back and run your eye along the line. Fill any hollows, firm up the hearting with a final tamping, and leave the wall to settle over winter. Come spring, walk it once with a bar and press any lifted stone back into place. Then put the kettle on and enjoy the fact that the boundary is now good for another fifty years.