A Princeton couple, Dave and Mary Bayerl plan to move into a home this year whose walls are filled with cordwood.
Yes, cordwood, like the kind you put into a wood furnace, though in this case the cordwood is sealed into the walls with concrete.
Known sometimes as cordwood masonry, cordwood construction or stackwall construction, a house of this design keeps the interior temperature very stable, says Dave Bayerl, who built it.
The Bayerls’ cordwood home is round, with 20 sides, and sits on the Bayerls’ 10 acres in Page Township about 25 miles north of Princeton. The Bayerls plan to put their conventional house in the city of Princeton on the market this spring. Once they sell it they’ll move into their house whose walls show the ends of wood stacked up, with masonry between the wood pieces. Hidden from view is an insulation in the center made of wood shavings mixed with lime.
The main work left at the cordwood home is to finish the mound septic system and drill a well.
Electricity has already been brought to the site and there is a wood stove in the cordwood home that the Bayerls have been using when they have gone to the home periodically. The heating system will be wood, with electricity as backup. But the stove to supply the heat permanently will be different than the one in there now.
Dave Bayerl is looking at buying a more energy-efficient wood gasification stove that will also have an electric heating element and either the heat from the wood or the electricity will heat water in a boiler. A wood gasification stove is touted as being twice as energy efficient as a traditional wood stove for multiple reasons. It has an insulated secondary burning chamber that reaches temperatures up to 2,000 degrees. That chamber burns wood gases that result from the primary wood burning and would otherwise just go out the chimney in a common wood-burning stove. If the Bayerls should be gone for a period of time, the electrical elements on the wood gasification stove would kick on.
In either case, whether the heat comes from the wood or the electricity, it will heat water in a boiler which will then circulate through tubes installed below the concrete slab floor of the cordwood home to produce radiant heat.
The cordwood home’s dimensions
The outside diameter of the Bayerls’ cordwood home is 50 feet, with the loft area in the center about 18 feet across. The highest part of the house is about 18 feet and is at the top of the loft which has the library, accessible by a wooden spiral staircase that Dave built. A bathroom sits directly below the library.
The Bayerls bought the lot in 2007 and cleared a space on it for the cordwood home. Bayerl made the cordwood out of aspen and basswood trees he cut on the property and peeled. He then cut aspen and basswood into rough lengths of 21 inches and let them dry. He chose these softer kinds woods, as opposed to a hardwood like oak, he explained, because the hardwoods would expand too much under moist conditions and break apart the walls of the home, Dave said.
The excavation and foundation work was done in 2008, Dave Bayerl describing the wet spring that year creating conditions for a “Noah’s ark” at the site. Bayerl laid a foundation that consisted of solid concrete on the bottom, with dry-stacked blocks on top of that, upon which he applied a skim coat of fiber cement on both sides of the blocks.
He installed underground utilities that include radiant heat tubes across the house. Over that he placed a vapor barrier and then sheets of foam insulation and then poured a concrete slab over that. He took photos of all the below-floor utilities so that he would know where to drill into the floor if there was ever a utility problem below the concrete floor.
He said he chose a concrete floor because it will be easy to clean.
Dave next built a wooden post and beam frame for the whole structure. He moved almost all of the wood frame pieces into place either by hand or with a hand-cranked lift that he rented.
The exception was two horizontal beams, which he had to hire a heavy equipment operator to hoist because of their weight. One was a 21 foot long, 8×10 beam weighing 600-700 pounds. The other was a 12-foot, 10×10-inch beam.
After he had framed everything in, including setting box frames into the framed-up walls for the windows, the next big task was to place cordwood into the 20 exterior sides. The main floor has six windows that are 59 inches square and three that are 29” x 59”. Small clerestory windows wrap around part of the outside of the loft.
After his rough-cut cordwood pieces were dry, Bayerl cut them to their final 18-inch lengths, using a homemade jig that turns a chain saw into a chop saw.
Dave employed many other clever techniques, including what is known as a water level to get the correct level for the foundation and slab. It works by stretching a clear hose between two points, filling the tube with a liquid and moving the far end of the tube up and down to get the water level to be the same at both ends.
He also had to do a lot of calculating in the construction because there were very few 90 degree angles in this 20-sided structure.
Installation of the cordwood walls took place over an approximately 100-day period in 2009. Dave’s brother Jim, of Ramsey, who had lost his job, assisted.
1. For each wall, Dave and Jim first laid down two big beads of cement, each bead about six inches wide and six inches high, along the top of the foundation between the two posts at each end of a wall section. They placed one bead along the outer top edge of the foundation and the other along the inner top edge. They used a cement mixture of sand, Portland cement and newspaper pulp. The newspaper pulp was made by mixing newsprint with water and churning it into a slurry and draining it.
2. Next, Dave and Jim placed wood shavings mixed with a lime to keep out insects, in the valleys between the beads of cement,for insulation.
Then Dave and Jim laid the cordwood, the majority of which was split to add variety in the looks of the wall and also reduce the amount of wood shrinkage. The cordwood was laid so that one end would appear on the outside of the house, and the other end on the inside.
3. Dave and Jim then applied more cement, enough to go above the ends of the cordwood, and then placed more shavings into the voids in the middle. Next, they laid more cordwood lengths atop the cement, with spaces between, and continued that process, eventually filling in each wall section.
The Bayerls also added a clever natural lighting effect, by interspersing the logs at certain points with what Dave called glass logs. Each consists of a wine bottle with its bottom showing on the inside of the walls, and a canning jar with its bottom showing on the exterior. A metal flashing goes around the two bottles to form the glass log before it is put into place in the wall. It not only lets in some natural light but also produces a colorful pattern on the wall.
Before Dave Bayerl began constructing the cordwood home, he built a scale model of it in his workshop for use as a guide.
Bayerl noted that while constructing the cordwood house was interesting, it was not without challenges which he called “trials and tribulations.” Besides all the calculations for the odd angles, he often worked in the cold, and he mentioned the difficult and tedious job of smoothing out the cement on each side of the wall. He used kitchen utensils like a spoon and butter knife for that.
And he said he got irritated by the building inspector making him build the structure even more heavy-duty than Bayerl had planned. “I overbuilt it (in the design in the first place) and he made me overbuild it a little more,” Bayerl explained. For example, the rafters ended up consisting of two 2 x 12-inch boards rather than one. However, having two planks for rafters did offer some advantages in the construction, Bayerl admitted.
Bayerl shopped around for deals on materials, getting a great deal on a double oven for the home. It has a convection oven on top and a conventional one on the bottom. Jay Frank, a sawyer in the Milaca area, supplied much of the post and beam material as well as other lumber for the home.
Bayerl built the kitchen cabinets and did the ceramic tiling for the countertops, as well as the interior carpentry which included installing the tongue-and-groove wood ceiling. He also built the interior walls, as well as the 30’x 56’ board and batten shed, and the porch with louvered windows.
Some people who have heard about the house, have asked how the electrical wiring is run in cordwood walls. The answer is it runs through a chase, or hidden space inside the top of the wall that runs around the interior. Bayerl needs only to remove some screws to pull back a panel in a particular area of the chase to get at the wiring. He can use what is known as a snake to move wire vertically in the walls.
How the project started
Bayerl admits that the words, “dream home,” apply to his cordwood home, and that he has always wanted a round house. “No one can box you into a corner” in a round house, he added.
A similar feeling about round houses has apparently run in the family of Dave’s wife Mary. He noted that she had a great aunt who hated corners and once had them rounded out in a home she lived in.
Mary last week said she likes the whole project but was a bit hesitant at first. “I wasn’t sure about cordwood walls,” she explained. “I thought of spiders and icky things. But now that it is done, it’s really nice.”
She also indicated that she suspected long ago that they would end up with a round dwelling. “He had a plan for a round house when we got married 36 years ago,” she explained.
The Bayerls’ plans for building the cordwood house began taking shape about six years ago when Dave read books on the subject by Rob Roy.
Then in the summer of 2006 the Bayerls got the chance to attend the Midwest Renewable Energy Fair in Custer, Wis. The annual three-day event is a mecca for alternative energy and energy-efficiency. “It’s a riot,” he said of this energy fair they attended, noting that it had 20 exhibition tents.