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Reprinted with permission from Back Home May/June 1998

Indigenous and owner-built in northern Wisconsin.

By
Jim Coonen and
Michelle Pezzi


Turning
the
Circle

Our house didn't begin in the round. In fact, Michelle and I began our planning some time ago for a cordwood house with an agreeable rectangle topped with a gambrel roof—one for which we would build our own trusses, using sections of locally milled 2" pine.

We even had some of the wood cut for that building when Michelle's brother offered us access to about 10,000 board feet of white pine from one of his logging jobs. With this amount of material on hand, we suddenly felt free to design something unique.

Round came to mind, not only because of Rob Roy's observation in Cordwood Masonry Housebuilding that a round house encloses over 27 percent more area than the same-perimeter square, but because we had second thoughts about our ability to make those complicated gambrel roof trusses and complete the house in the short building season of northern Wisconsin, given our modest construction skills.

We drew up our plans on graph paper for a 40'-diameter house modeled somewhat after a cordwood home we'd seen in Harrowsmith magazine. After taking the 16" cordwood lengths into consideration, the inside diameter came to 37' 4", offering a usable interior space of 1,094 square feet. Our original rectangular barn-roof vision was now officially a single-story, 16-sided circle.

Our design took into consideration the importance of passive sunlight, especially during our cold winter months. We have no windows facing north—the glass begins on the east and west walls and continues to the south where there is a large picture window. In the coldest months, the windows are sealed off at night with
pull-down shades and heavy thermal curtains hung over the shades, offering an indescribably cozy feeling.

We figured the height of the house at about 15' at center and 7' 3" at the top plate of the walls, giving a nearly 4-in-12 roof pitch. We also planned for a skylight and vents in the apex of the roof, for light and air circulation.

The cordwood masonry technique is one we've favored for a long time. Richard Flatau, the author of Cordwood Construction: A Log End View, lives in our area and has taught building workshops in the past. The technique involves mortaring together debarked, split, and thoroughly dried firewood-sized logs to make a wall that can be used to fill the space between built-up corners or posts and beams or laid up in a solid run to describe curves or a complete circle.

While our cordwood was drying—a process that took a full year—we busied ourselves excavating and pouring the concrete slab foundation and assembling window frames and rafters from the milled lumber we had. Since our original truss stock consisted of 2 x 12s, we had to bolt boards together to accommodate the 23' span needed to stretch the distance from the center to the rafter tails, including a 30" eave overhang. That lumber furnished us with 16 main rafters, plus 16 intermediates to place between the mains.

But our friend and paid helper Greg Stevenson still had some concern over snow load, so he suggested we put jack rafters between the full-length supports by fastening them to cripples nailed to the rafters about one-third of the way up from the tails. These, too, were cut from existing lumber.

To make the uprights needed to support the main rafters and define the walls of the 16-sided circle, we milled 8 x 8 posts on three sides so we could join two posts face-to-face and fasten them together on the sides with flat boards. This allowed us to once again make use of the materials we had on hand and produced substantial 8" x 16" posts that matched the cut length of our cordwood and offered rounded, natural-looking faces both outside and in. The posts were mounted on 3/4" rebar pins set into the concrete slab at the time of pour. To keep the posts from drifting, a socket drilled into the bottom of each post fit over the 5" stubs left protruding from the foundation. Once the uprights were secured and vertically plumbed, we could set the top plates by leveling them and by comparing diagonal measurements in each bay to check for square. To give ample strength to the framework, the top plates were doubled and the joints staggered slightly.

On June I, 1996, with the post-and-beam frame complete, it was time to tackle the cordwood infill. Many builders prefer to finish the roof first for weather protection, but we chose to just get on with the walls. Before starting, we tacked 4" strips of fiberglass along the inside faces of the posts and plates to seal against air infiltration. To lay the first course of cordwood, we began by placing two broad, parallel rows of mortar for several feet along the top plate, hard against one of the
posts.

This isn't a conventional mortar mix, but a special cordwood masonry blend favored by Rob Roy; it consists of nine parts sand, three parts sawdust soaked overnight, three parts hydrated lime, and two parts portland cement. Other builders have alternative recipes that use masonry cement and less lime, or more sawdust and less sand, but the point is to make a workable, slow-setting matrix that resists slumping and bonds to the wood without excessive shrinking, which later causes cracks and gaps.

Split logs were set in the mortar bed, 3/4" to 2" apart, and laid parallel so the spaces between were even. The mortar-bed rows were continued another 3' or 4' and the process repeated until one full course stretched post to post. We filled the space between the mortar rows with an insulation mixture of one part hydrated lime to three parts dry sawdust from the mill.

With the first course done, the second was laid in similar beds of mortar set atop the ends of the logs, with limed sawdust in between. Heeding the written advice of several stackwood experts, we took care to not allow the mortar beds to touch, since that would provide an easy path for heat loss. Likewise, we kept the logs separated to discourage wet rot and allow room for the pointing blade to pass between, a necessary step in packing the moist mortar around the log faces later on.

In places where windows and a door were planned, we just nailed the ready-made frames to the top plates, anchored them in the mortar, and built the walls around the frames. By the middle of July, all 16 wall panels were complete.

Next, the roof went up. The rafters were set on the posts to the outside, and on a ring-beam framework we built in a 12'-diameter circle on the inside, which surrounds the kitchen. This circular load-bearing structure was made from 8 x 8 posts pinned to the concrete below and joined at the top with 4 1/2' horizontal beams. There's a hefty 16" x 24" footing beneath these posts and the ones at the outside to support the additional weight of the heavy members.

The roof was sheathed not in plywood but with 1" board cut from our white pine harvest. Because of the
radial layout of the structure, there was very little waste, since a long tailing trimmed from one place usually fit somewhere else higher up on the roof. Normally, circular roofs are a geometric nightmare with their compound angles, but the strip sheathing made the job much more manageable. With help from our builder friend Jeff Ellis and his wife, we were able to finish the sheathing, venting, and shingling in a week.

With the house dried in, we were able to work on hanging and trimming the doors and windows and finishing the fascia before moving inside. Michelle—using books borrowed from the library—built all the cabinets, doors, and interior features from our private lumber stock. This saved us a bundle of money while using natural, locally indigenous materials, including the hardwood flooring. If we had had to buy these things from a builder's supply, we could only guess how much more the project would have cost. . . and we'd certainly not be enjoying custom carpentry.

We both wanted a home that would fit unobtrusively on our 40 wooded acres and would blend in with rather than stand out from the surrounding area. An existing logging road from years past allowed us to manage by cutting only a few small trees in the vicinity of the house, and we were able to use river rock to cover the foundation. All told, the entire house, not including the well or septic system, came to $17.28 a square foot.

The long and short of it is that building with cordwood is a slow, somewhat arduous task. I liken it to riding a bicycle down a country lane when you could be driving the interstate at 70 miles per hour. But every method of construction has its peculiar drawbacks and advantages, and we both feel that the experience, enjoyment, and balance of the work is just as important as getting it done. And, once our walls were complete, they were finished—inside, outside, and down the middle.

 

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