Cordwood Homes: Natural Beauty and Energy Efficiency
Cordwood masonry, or stackwall construction, is an excellent do-it-yourself way to build a house. It’s inexpensive, labor intensive and does not require any special skills. Local materials, which are sometimes scraps, can be used, making it an environmentally friendly building method.
In Siberia and Greece, cordwood buildings date back 1000 years, although there is no clear beginning of their history. They have also been found in Scandinavia. In the 1800s, cordwood homes and barns were cropping up in the US’s upper midwest and Canada. They were called Depression Housing in the 1920s and 30s. Building materials were expensive and unavailable, and these were made with local materials.
Cordwood construction process
Logs 6”-24” long are placed in a bed of mortar with the ends sticking out just a bit. Mortar is placed between each log only at the two ends, making a space in the middle, which is traditionally filled with sawdust and lime for insulation. Spray foam can also be applied as the wall gets built. The construction method essentially creates two walls that are insulated in between. Here are some excellent photos of the cordwood construction process.
Wood scraps can be used for this. Sometimes, if you heat with wood, there are pieces too big to burn and too gnarly to split. These are great candidates for a cordwood wall. One homeowner built his cordwood home from discarded telephone poles. If you have a wooded lot, you can cut your own.
Other sources are downed trees in the forest or scraps from a wood mill. Whole, round logs may need to be split so they dry out evenly. All wood must be completely seasoned. If it dries and shrinks in the wall, air can infiltrate. Also, wood with moisture in it may rot once installed.
The cement mortar can have sawdust and/or paper added, recycling even more materials. This also cuts back on concrete, which is very energy intensive to make. The more eco-friendly option is cob (mud) for mortar. This is another local material, and cracks can be repaired quickly and easily.
The shape, design, and efficiency of cordwood houses
Cordwood lends itself to a circular structure, which is a very efficient use of space. Another option is a post and beam frame that is filled in once the roof is on. Instead of corner posts, squared logs called quoins can be stacked for strength, and cordwood masonry walls built in between them.
Decorative touches are easy to add. Arches above doorways and windows are easy to build. Colorful glass bottles can be placed in mortar along with the logs. Other sturdy wall decorations can be added into the mortar as permanent wall art.
Cordwood homes are energy efficient, because the concrete acts as thermal mass holding heat that radiates into the house. Because there are no studs, air is not transferred from inside to outside (thermal bridging). A 16” wall has an approximate R-value of 20, and a 24” wall is about R40. A round cordwood home heats and cools easier, since air flows without wall obstructions.
Aside from being energy efficient, cordwood houses have great acoustic qualities, and they have a natural, rustic look to them. They fit in well in a wooded setting.
If this is a DIY project, professionals will need to be called in for the foundation, plumbing and wiring. Building permits will also need to be acquired, and code must be followed. Other than that, cordwood masonry is a simple, inexpensive way to build an energy efficient home with a natural look.