Cordwood construction (also called cordwood masonry or cordwood building, alternatively stackwall or stovewood particularly in Canada) 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. This technique can be made to use a wide variety of locally available materials at minimal financial cost, and is a classic example of trading a higher raw labor requirement for technical ease and cost-efficiency of building (a common feature in back-to-the-land alternative/traditional building methods).

Walls are usually constructed so that the log ends protrude from the mortar by a small amount (an inch or less). Walls typically range between 8 and 24 inches thick, though in northern Canada, some walls are as much as 36 inches thick.

Cordwood homes are attractive for their visual appeal, 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. 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.

Remains of cordwood structures still standing date back as far as one thousand years in eastern Germany. However, more contemporary versions could be found in Europe, Asia, and the Americas. There is no detailed information about the origins of cordwood construction. However, it is plausible that forest dwellers eventually erected a basic shelter between a fire and a stacked wood pile. In the work of William Tischler of University of Wisconsin, he states that "current" cordwood probably started in the late 1800s in Quebec, Wisconsin, and Sweden. He believes that the technique started in these areas around the same time.

Cordwood construction is an economical use of log ends or fallen trees in heavily timbered areas. Other common sources for wood include sawmills, split firewood, utility poles (without creosote), split rail fence posts, and logging slash. It is more sustainable and often economical to use recycled materials for the walls. Regardless of the source, all wood must be debarked before the construction begins. 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. Acceptable woods also include Douglas fir, western larch, Eastern White Pine, and Spruce Pine.

Less dense and more airy woods are superior because they shrink and expand in lower proportions than dense hardwoods. Most wood can be used in a wall if it is dried properly and stabilized to the external climate's relative humidity. Furthermore, while log ends of different species can be mixed in a wall, log-ends of identical species and source limit expansion/contraction variables.

Various experts advise different recipes for mortar mix. 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. Builder's lime makes the wall more flexible, breathable, and self-healing because it takes longer to completely set than cement. Portland cement chemically binds the mortar and should be either Type I or II. 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.

Depending on a variety of factors (wall thickness, type of wood, particular mortar recipe), the insulative value of a cordwood wall, as expressed in R-value is generally less than that of a high-efficiency stud wall. Cordwood walls have greater thermal mass than stud frame but less than common brick and mortar. This is because the specific heat capacity of clay brick is higher (0.84 versus wood's 0.42), and is denser than airy woods like cedar, cypress, or pine. However, the insulated mortar matrix utilized in most cordwood walls places useful thermal mass on both sides of the insulated internal cavity, helping to store heat in winter and warm slowly in summer. Thermal mass makes it easier for a building to maintain median interior temperatures while going through daily hot and cold phases. In climates like the desert with broad daily temperature swings thermal mass will absorb and then slowly release the midday heat and nighttime cool in sequence, moderating temperature fluctuations. Thermal mass does not replace the function of insulation material, but is used in conjunction with it.