Another recipe uses 3 parts sand, 2 soaked sawdust, 1 Portland Cement and 1 Hydrated Lime intended to have the advantage of curing slower and displaying less cracking. Portland cement chemically binds the mortar and should be either Type I or II. Builder's lime makes the wall more flexible, breathable, and self-healing because it takes longer to completely set than cement. One recipe which has proven to be successful since 1981 is 9 parts sand, 3 sawdust, 3 builder's lime (non-agricultural), 2 Portland cement by volume. Various experts advise different recipes for mortar mix. Furthermore, while log ends of different species can be mixed in a wall, log-ends of identical species and source limit expansion/contraction variables. Most wood can be used in a wall if it is dried properly and stabilized to the external climate's relative humidity. Less dense and more airy woods are superior because they shrink and expand in lower proportions than dense hardwoods. Acceptable woods also include Douglas fir, western larch, Eastern White Pine, and Spruce Pine. While many different types of wood can be used, the most desirable rot resistant woods are Pacific yew, bald cypress (new growth), cedars, and juniper. Regardless of the source, all wood must be debarked before the construction begins. It is more sustainable and often economical to use recycled materials for the walls. Other common sources for wood include sawmills, split firewood, utility poles (without creosote), split rail fence posts, and logging slash. Wood Ĭordwood construction is an economical use of log ends or fallen trees in heavily timbered areas. He believes that the technique started in these areas around the same time. In the work of William Tischler of University of Wisconsin, he states that "current" cordwood probably started in the late 1800s (decade) in Quebec, Wisconsin, and Sweden. However, it is plausible that forest dwellers eventually erected a basic shelter between a fire and a stacked wood pile. There is no detailed information about the origins of cordwood construction. However, more contemporary versions could be found in Europe, Asia, and the Americas. Remains of cordwood structures still standing date back as far as one thousand years in eastern Germany. 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. As a load-bearing wall, the compressive strength of wood and mortar allows for roofing to be tied directly into the wall. 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. 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. In the more common M-I-M, and unlike brick or throughwall masonry, the mortar does not continue throughout the wall. 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). There are two main types of cordwood construction, throughwall and M-I-M (mortar-insulation-mortar). Cordwood construction can be sustainable depending on design and process. Wood usually accounts for about 40-60% of the wall system, the remaining portion consisting of a mortar mix and insulating fill. Walls typically range between 8 and 24 inches thick, though in northern Canada, some walls are as much as 36 inches thick.Ĭordwood homes are attractive for their visual appeal, maximization of interior space (with a rounded plan), economy of resources, and ease of construction. Walls are usually constructed so that the log ends protrude from the mortar by a small amount (an inch or less). This technique can use local materials at minimal cost. Cordwood construction (also called cordwood masonry or cordwood building, alternatively stackwall or stovewood) is a term used for a natural building method in which short logs are piled crosswise to build a wall, using mortar or cob to permanently secure them.
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