Cordwood masonry, also known as stackwall or stovewood construction, is a building technique that uses short lengths of debarked firewood laid crosswise in a mortar matrix. The ends of the wood pieces are exposed on both sides of the wall, creating a distinctive patterned appearance. Cordwood walls provide good insulation value (R-1.0 to R-1.5 per inch of wood length) and thermal mass from the mortar. The technique is well-suited to owner-builders, as it requires no specialized equipment or skills.
The wood used in cordwood construction is debarked softwood or hardwood, cut to uniform lengths of 30 to 60 centimeters (12 to 24 inches). The wood must be thoroughly dried, with a moisture content below 20 percent, to prevent shrinkage and cracking after installation. Softwoods such as cedar, pine, and fir are preferred for their lower shrinkage rates and natural rot resistance. The mortar is a mixture of Portland cement, sand, and lime, with sawdust or vermiculite sometimes added for insulation. The mortar is mixed to a stiff consistency to support the weight of subsequent courses.
The wall is built on a Concrete Foundation or stone Concrete Foundation with a damp-proof course. A base layer of mortar is spread, and wood pieces are pressed into it, leaving a 2 to 5 centimeter (1 to 2 inch) gap between pieces. The gaps are filled with a mortar mix, and the wall surface is finished flush with the wood ends. Each course is allowed to set before the next is added. The wall is built in a running bond pattern, with the wood pieces staggered from course to course. The interior and exterior are finished with a breathable plaster or left exposed.
Cordwood construction is used for homes, cabins, garden walls, sheds, and studio spaces. The thermal mass of the mortar combined with the insulation of the wood provides a comfortable indoor environment. Maintaining a consistent wood length is critical, as the wall's insulation value depends on the depth of the wood pieces. Earthbag Construction and cordwood masonry are often combined in a single building, with Earthbag Construction for the foundation and lower walls and cordwood for the upper walls.