Stone Foundations and Dry-Laid Masonry

Why stone

Wood rots where it stays wet; stone doesn’t care. Every durable timber tradition in this course - stave churches, log houses, sod-roofed farm buildings - keeps wood off the ground on stone. Historic log buildings sat on sill logs laid on a continuous course of flat stones or on stone piers at the corners and along the walls, which let air circulate under the sills ¹.

Piers or footings

Piers (a footing stone and a stack of flat stones, or a concrete pier on a footing pad) suit unheated outbuildings - sheds, saunas, woodsheds, a small cabin. Raise the sill 12-18 inches above grade so splash and snow don’t keep it wet. Frost can heave a shallow pier, so set it on firm, well-drained subsoil, never topsoil, or go below frost.

Continuous footings below frost suit heated buildings. Wisconsin’s Uniform Dwelling Code requires a dwelling’s footings to go below frost penetration or at least 48 inches, whichever is deeper, and forbids placing them on frozen material ². Frost-protected shallow foundations with insulation are an engineered alternative allowed under the code.

Repairing old ones: when a historic pier settles or a sill rots, jack the building, rebuild the pier on a proper bearing, and replace the sill section; keep the gap under the building open for ventilation ¹.

Building a dry stone wall

Dry stone walling uses no mortar; the wall stands by gravity, friction, and good placement ³. The same principles apply to a dry-laid stone foundation, a retaining wall, or a field wall.

1. Foundation: strip topsoil to firm subsoil; set the largest stones at the base ³, each laid length into the wall, not along it.
2. Two faces and hearting: build two face lines with the outer faces flat; pack the middle tightly with small stones (hearting) placed by hand ³.
3. One over two: each stone crosses the joint between two below. Running vertical joints split walls.
4. Through stones: about halfway up, lay long stones through the full width, tying both faces together ³.
5. Batter: the faces lean inward as the wall rises, narrowing toward the top; roughly 1:6 to 1:10 ³. A pair of wooden batter frames at each end with strings between them keeps the line.
6. Pinning: small wedge stones shim face stones solid from behind, never from the face, where they would work loose.
7. Coping: finish with heavy cope stones set on edge across the top to weight and lock the wall.

Each face stone should slope slightly down toward the outside to shed water. Repair a dry wall dry: don’t patch with mortar ³.

Dry stone under buildings

A dry-laid foundation wall or pier works for a sauna or outbuilding; for a heated house in Wisconsin it’s a code question - the footing must be below frost, and an engineer or inspector will want details. Many builders pour a concrete footing below frost and face the visible portion with stone.

What to take from this

Keep timber off the ground on stone: piers for unheated outbuildings, sills 12-18 inches above grade on firm subsoil; continuous footings below frost or at least 48 inches for Wisconsin dwellings. Dry stone walls stand by placement: biggest stones at the base laid into the wall, two faces with tight hearting, one over two, through stones halfway up, an inward batter, pinning from behind, and a heavy cope.