How To Build A Cordwood House

Categories: Construction Methods

Cordwood homes are attractive for their visual appeal, maximization of interior space (with a rounded plan), economy of resources, and ease of construction. Wood usually accounts for about 40- 60% of the wall system, the remaining portion consisting of a mortar mix and insulating fill.[1] Cordwood construction can be sustainable depending on design and process. There are two main types of Cordwood Construction, Throughwall and M-I-M (mortar-insulation-mortar). In Throughwall, the mortar mix itself contains an insulative material, usually sawdust, chopped newsprint, or paper sludge, in sometimes very high percentages by mass (80% paper sludge/20% mortar). In the more common M-I-M, and unlike Brick or Throughwall masonry, the mortar does not continue throughout the wall. Instead, three- or four-inch (sometimes more) beads of mortar on each side of the wall provide stability and support, with a separate insulation between them. Cordwood walls can be load-bearing (using built-up corners, or curved wall designed) or laid within a post and beam framework which provides structural reinforcement and is suitable for earthquake-prone areas. As a load-bearing wall, the compressive strength of wood and mortar allows for roofing to be tied directly into the wall. Different mortar mixtures and insulation fill material both affect the wall's overall R value, or resistance to heat flow; and conversely, to its inherent thermal mass, or heat/cool storage capacity.

Walls are usually constructed such that the pieces of wood are "proud" of (protrude from) the mortar by a small amount (an inch or less). Walls typically range between 12 and 24 inches thick, though in northern Canada, some walls are as much as 36 inches thick.

Here's another build under way in an off-grid cordwood round house!:  

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