Building a Cordwood House

By Rob Roy
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Two Thousand Square Feet for $27,000 . . . and a $75 Fuel Bill!
Two Thousand Square Feet for $27,000 . . . and a $75 Fuel Bill!
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The 16' screed board spans from the perimeter footings to the 7' diameter masonry stove foundation. This shows Insulation, mesh, and footings.
The 16' screed board spans from the perimeter footings to the 7' diameter masonry stove foundation. This shows Insulation, mesh, and footings.
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Rob at work on a cordwood masonry
Rob at work on a cordwood masonry
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The sand pad is compacted in three runs of about 6
The sand pad is compacted in three runs of about 6"" each.
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Dry stack corner blocks (8
Dry stack corner blocks (8"" x 8"" x 16"") like cordwood in the bermed wall.
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Jaki Roy uses a stainless steel butter knife to smooth the mortar.
Jaki Roy uses a stainless steel butter knife to smooth the mortar.
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The sun-facing cordwood masonry wall made easy. First lay an insulated double bed of mortar on the slab.
The sun-facing cordwood masonry wall made easy. First lay an insulated double bed of mortar on the slab.
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Using a trowel, apply surface bonding cement to a dampened wall.
Using a trowel, apply surface bonding cement to a dampened wall.
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Then, tie the inner and outer beds together with log ends. Repeat.
Then, tie the inner and outer beds together with log ends. Repeat.
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The masonry stove is 5' in diameter downstairs and reduces to 4' upstairs. Flues crisscross through the masonry to increase conduction.
The masonry stove is 5' in diameter downstairs and reduces to 4' upstairs. Flues crisscross through the masonry to increase conduction.
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Place waterproofing membrane vertically on the bonded walls.
Place waterproofing membrane vertically on the bonded walls.
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The octagonal post-and -beam frame cuts the radial rafter spans in half. The masonry stove acts as a load-bearing column at the center of the home.
The octagonal post-and -beam frame cuts the radial rafter spans in half. The masonry stove acts as a load-bearing column at the center of the home.
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The French drain is made of perforated flexible tubing.
The French drain is made of perforated flexible tubing.
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Sixteen rafters go all the way to the stove; the others stop at the octagon.
Sixteen rafters go all the way to the stove; the others stop at the octagon.
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We apply waterproofing membrane to the primed spruce deck.
We apply waterproofing membrane to the primed spruce deck.
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After laying a layer of 6 -mil black polyethylene over the foam insulation, we install a 2
After laying a layer of 6 -mil black polyethylene over the foam insulation, we install a 2"" crushed stone drainage layer, then straw, then 7' - 8"" of earth.
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We place 4
We place 4"" of extruded polystyrene on the top of the membrane, protecting it from the freeze-thaw cycling.
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Diagram of the house.
Diagram of the house.
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Construction details
Construction details

Visitors shake their heads when I tell them that we are heating Earthwood, our 2,000-square-foot home near the Canadian border, for $75 this winter. It’s hard to tell if they’re really impressed or think I’m trying to pull the wool over their eyes. But I really get their interest when I explain further that the house maintains a steady temperature, summer and winter, with no “spikes” in the temperature curve. North Country folks are used to waking up to a chilled home on subzero winter mornings.

There’s no magic involved, and no attempt at deceit. Earthwood’s performance is the result of employing several design characteristics not usually combined in American homes: a round shape, earth sheltering, cordwood masonry, solar orientation, and a 23-ton wood-fired masonry stove. And the cost? About $27,000 total, including labor and materials. Grudgingly, I admit that $6,500 of this figure went toward hired help; otherwise, my wife Jaki and I did the work ourselves. And $5,000 of the $27,000 represents the value of materials donated by manufacturers for field-testing purposes, but I’ve included them to give a true idea of cost. In 1995, an Earthwood-type home can be built for a materials cost of about $15 per square foot.

A Round House

The other building species (birds, bees, beavers, etc.) know instinctively that a round house is the most economical to build and the easiest to heat. Backed by millions of years of experience, a course in geometry would be wasted on animal architects. Same with so-called primitive man. Where materials are scarce and time is at a premium, it does not occur to many tribes to build any shape other than round. A round house encloses 27.3% more space than the most efficient rectilinear house, which is square. But Americans don’t even build square houses anymore. Typically, the American home is twice as long as it is wide, and a round house enjoys a space percentage gain of 43% compared to such a rectangle! The same amount of time, materials, and labor (particularly when building with masonry units) yields a home that has 43% more space. And, when heat loss through skin area is considered, it’s approximately 43% easier to heat on a per-square-foot basis.

The outside diameter of Earthwood is 38’8″. With 16″ thick walls, the inner diameter of 36′ yields a usable internal area of 1,018 square feet on each of the two stories, just over 2,000 square feet total.

  • Published on Apr 1, 1995
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