Cordwood Masonry Walls — Round-Log Infill with Mortar

Background & Cultural Context

Cordwood masonry, also called stack-wall construction or stovewood construction, is a building technique in which short lengths of debarked log are laid like brick between mortar joints to form a wall. The name comes from the standard firewood-cord dimension — the logs used are roughly the same length and diameter as split-firewood pieces. The technique has independent documented origins in nineteenth-century rural North America (particularly Wisconsin, Quebec, and Saskatchewan) and in Scandinavia and Siberia, where the same approach was used opportunistically with leftover small-diameter timber from felling operations.

The wall section is a sandwich. Two parallel mortar joints, typically eight to ten centimeters wide each, run along the inside and outside faces of the wall. Between them sits an insulating cavity filled with sawdust, wood shavings, lime-cement-sawdust mixture, or another vapor-permeable infill. The log ends protrude through both mortar joints; in a forty-centimeter wall, the inner mortar joint, the twenty-centimeter insulation cavity, and the outer mortar joint each account for a portion of the thickness. The visible log ends on both faces are characteristic of the building style.

Wood choice matters significantly. Softwoods (cedar, pine, spruce, larch) are preferred for their dimensional stability and natural rot resistance; hardwoods are avoided because they expand and contract dramatically with humidity and break the mortar bond. Logs are debarked while still green, then air-dried under cover for one to three years before construction. The moisture content at construction should be below fifteen percent; wetter logs continue drying inside the wall and develop gaps as they shrink. Standard log diameter is ten to twenty centimeters; standard length matches the wall thickness, typically thirty to fifty centimeters.

The technique has been continuously taught in North American owner-builder schools since Rob Roy's 1980 book Cordwood Masonry Houses brought the form into the modern self-build canon. Cordwood houses are now built across Canada, the northern United States, parts of Europe, and Australia. The form is permitted under alternative-construction provisions in most US state codes and is explicitly addressed by Canadian National Building Code provisions for log construction.

Thermal performance varies with the cavity insulation. A typical forty-centimeter cordwood wall with sawdust-lime cavity insulation achieves measured R-18 to R-22 — better than a standard timber-framed wall and competitive with high-spec modern construction. The high mass of the mortar joints (which represent roughly half the wall surface area) gives the building useful thermal-mass behavior in addition to the insulation value. The log ends themselves are modest thermal bridges; the design is a balance between thermal performance and the visual character of the exposed log ends.

Modern Application

A modern cordwood build typically follows this sequence. (1) Source and dry the cordwood — one to three years before construction. A 100-square-meter house needs roughly eight to twelve cords of suitable softwood. (2) Build a frost-protected concrete or stone foundation and an interior post-and-beam frame to carry the roof load; cordwood is generally treated as infill rather than load-bearing in modern code-compliant builds. (3) Mix mortar at site (Portland-lime-sand-sawdust in roughly 1:1:3:3 ratio is a common formula). (4) Lay the wall in courses, working the mortar joints flush on inside and outside and filling the insulation cavity as you go.

Building speed is modest. A two-person team typically lays one to two cubic meters of wall per day, meaning a small house wall takes thirty to sixty days of dedicated work. Cordwood is well-suited to weekend and seasonal building — the mortar can pause between courses without difficulty, and unfinished walls can sit through winter under tarp protection.

Cost economics are favorable for the owner-builder. Materials run roughly forty to sixty percent of equivalent conventional construction. The largest cost is foundation and roof; the cordwood walls themselves are inexpensive if the timber is site-felled or locally salvaged. Many cordwood builders use storm-downed trees, bug-killed pine, and other non-commercial timber that would otherwise be burned or chipped.

Honest limits: cordwood is not appropriate in seismic zones without engineered reinforcement. The wall section is rigid but the connection to foundation and roof needs continuous-load-path design that is not intrinsic to the building technique. Humid climates produce ongoing mortar-bond stress as the wood expands and contracts; some checking and small mortar cracks are normal even in well-built walls and require periodic re-pointing every fifteen to twenty-five years. Avoid building cordwood in regions with active wood-boring insects unless the wood has been kiln-dried or chemically treated. Permitting in suburban jurisdictions can require engineering-stamp sign-off; rural areas are typically more permissive.

Maintenance over the building's life is modest but not zero. Periodic re-pointing of mortar joints, particularly on the weather-facing wall, is the main ongoing task. Some checking and small mortar cracks are normal even in well-built walls — softwood logs naturally cycle through small expansion and contraction with humidity, and the mortar joint tolerates this without structural compromise but does develop hairline cracks that need refilling. A well-built cordwood wall maintained on a fifteen-to-twenty-five-year re-pointing cycle has a documented service life of one hundred years or more.