Building with Cordwood Masonry: From Tree to Wall
“Cordwood masonry is an old building technique whereby walls are constructed of short logs (called “log-ends”) laid up widthwise in the wall within a special mortar mix. The wall drives excellent insulation and thermal mass characteristics from insulation sandwiched between the inner and outer mortar joints. Cordwood houses are low in cost, use indigenous materials, and are easy and fun to build.”
Photos of natural-looking outdoor sheds and garden rooms inspired us to try building with cordwood. As an alternative to plywood construction, the masonry walls should be able to withstand mountain weather and termites that typically destroy wood construction.
There is no doubt that cordwood masonry building is a beautiful and natural alternative for outdoor living.
In November, 2008 while taking a Sustainable Landscaping course at Cabrillo College, a Saturday field-trip to a nursery near downtown San Jose led to the discovery of a cordwood structure that was nicely framed and securely made. I knew that I wanted to try this style of construction on the outdoor laundry room. I also recognized the difference between the look of split wood logs vs. rounded logs. We preferred the rounded log style.
Before starting the project, online research was done to learn what the mortar compound was made from and how to apply it. Not much information was available, and different articles offered bits and pieces of the application process. Our project would be an experiment.
The garage and laundry room before it was improved:
In April 2009, black locust trees were cut down in the front to improve the drainage and prepare for the circular driveway. These logs were the perfect material to use for the masonry studio. They had the chance to dry for a year before we cut them into smaller logs for the project.
June 13 2010 we ordered wine bottles for the walls from The Home Brewery: 24 Amber, 12 blue, 24 clear and 24 green. The amber and cobalt blue were 750 ml, and the clear and green were 187 ml. Cost of all the bottles with shipping was just around $175.00. We wanted to add color bottles in the walls for added light and uniqueness.
From June 26, 2010 – June 28, 2010 a lot of work was accomplished. Ian, our building contractor, was hired to repair the foundation and build the framework. We had purchased vintage wavy-glass windows, and we wanted to add them around the laundry room. It only took Ian a few days to accomplish his tasks. It took us much longer to finish the two cordwood walls.
In addition to adding an improved foundation to support the weight of the walls, we were able to start cutting the logs and cementing in a few rows. The materials for the mortar include sand, concrete mix, Portland cement, lime, and saw dust. Bags of saw dust were periodically picked up from the Saw Dust Shop in San Jose. They kindly let me show up and collect the saw dust which was paint free.
The locust logs were measure precisely. The bark was removed, and it made for great kindling. The large logs were cut with a chainsaw, and the smaller pieces were cut with a chop saw. Any gaps were filled in with the bottles. Each log was coated with linseed oil for added protection. Only a few rows at a time were added so the mortar could dry.
At the end of July the side of the wall was finished. In August, 2010, the front was started. Mushroom shape landscape lights were added around the side and front to match the look of the bottle glass. Plastic tubes were mortared into place, and the landscape lights fit through. The wiring was connected to the timer.
In September, the wood was primed for painting. Also, the mortar residue was scrubbed off the wood and bottles using muriatic acid and a steel wool brush.
In October, the front of the studio was being designed with a planter bed and walkway using river rocks and cement. The drainage downspout was plumbed to go under the walkway and drain into an underground pit that the previous owner had dug out and filled with gravel. This was perfect.
In November, work continued on the planter bed, and the river rock walkway was started.
In January, 2011 finished the planter bed and planted a barrel cactus.
February 2012. The only thing left to do was to put a special window or stained glass window above the door.
It was a great experience to work with mortar and cordwood to create something unique. It is a process to mix the compound and build up the walls slowly and evenly. If the mixture is changed, the color of the cement will also change, being more grey or brown depending on the quantity of cement. Cleaning off the mortar also makes a huge difference when it is done early before it dries on the wood and glass. The acid will stain the cement and make it change color around the edges.