Why a dry stone wall stays up

No mortar, barely a foundation, and most of the walls on this hill are older than the farmhouses. Notes from three winters rebuilding the top field.

Ffion Maddox · Field notebook

Every wall here is really two walls leaning on each other. Each face is built from the biggest stones you can lift, laid with their length running into the wall rather than along it, and every metre or so a long throughstone crosses the whole width and ties the faces together.1

The faces are not upright. They lean inward on a batter, narrowing from about 80 cm at the footing to 35 cm under the top, so the weight of each course presses the wall into itself instead of out towards the field.

What fills the middle matters as much as what you see. Packing the gaps with hearting, small stones placed by hand and never tipped in from a bucket, is what stops the faces from rocking. A wall with poor hearting looks perfect for a year, then bellies out after the first hard frost.

Then the top. A row of cope stones set on edge, tight together, locks the last course down and sheds water off the wall. Ours come from the old quarry on Pen Isaf, which gives them a blue cast against the brown faces below.2

None of this is clever. It is gravity, friction and patience, and most of a waller's job is saying no to the wrong stone. On a good day two of us rebuild about four metres.