A QUICK AND INEXPENSIVE SOD IGLOO
How author dug in for the winter to avoid leaving his new homestead in the
woods of Vermont, including diagrams of front and side views, how it was done, photographs.
REPORTS FROM THEM THAT'S DOIN'
How I dug in for the winter . . . to avoid leaving my new homestead in the
woods of Vermont.
by Burnell Lippy
My predicament was starkly simple. With winter just a few months away, I had
only a couple of hundred dollars, some basic tools, and my own two hands with which to build myself a temporary shelter for
the cold season. To compound the problem, I wanted more than a mere refuge ... I hoped to create a dwelling that was not only
warm and comfortable, but also structurally graceful and in harmony with the landscape of the northern Vermont forests where
I make my home. After a good bit of research, I became convinced that I could fulfill all my expectations by building a semi-underground
house: a sod igloo.
I first encountered this uncomplicated design in the classic book Shelter
(Shelter Publications, 1973). Ole Wik's description and photos of his sod "iglu", and Keith Jones's article about the building
of a similar house in Alaska, convinced me that such a dwelling could combine the elements of efficient design with a simple
sort of grace . . . and could do so while remaining unobtrusive.
Of course, these crude earth-insulated structures aren't generally used as
permanent homes. Most often, they're intended as quick, comfortable, recyclable shelters that will serve until something more
conventional can be built . . . or — on occasion — as auxiliary retreats, hunting cabins, and such. But with winter
approaching, I knew the sod igloo would meet my needs and fall within the limits of my financial resources. In fact,
in 1978 (the year I built it) the materials for my earthen cabin cost around $150 . . . about the same as had the goods which
went into the canvas tipi I'd lived in previously. (And as someone who has experienced cold weather when protected by both,
I'll guarantee that soil beats canvas as an insulating material every time!)
WHAT I DID . . .
It stands to reason that a sod igloo would be inexpensive . . . since many
of the raw materials that make up such a structure can be had free. The necessary earth was, of course, stockpiled as I dug
out the outline of the house.
I obtained wood for the frame, roof, and walls from nearby spruce and balsam
firs. (Many of the required slim, straight poles can be culled from stands of young trees growing too close together for proper
development. Because such an overpopulated copse produces trees that are tall, thin, and straight, a single thicket can provide
an excellent supply of building materials and the opportunity to give Mother Nature a hand by thinning out her overabundance.)
The only other construction supplies I needed were nails, spikes, staples,
a few screws and hinges, 6-mil black plastic sheeting for the vapor barrier, glass (you could use plastic instead) for the
windows, planking for the floor, and 2 X 6's for framing the door and windows. And since I was able to salvage some of these
materials and trade for others, my costs remained low.
My tools were basic, but well suited to the job at hand. The collection consisted
of a saw, hammer, axe, hand drill, pick, shovel, drawknife, screwdriver, and staple gun. I also used a level and square .
. . but only when laying the floor and hanging the windows. Peeled logs don't have many planes or right angles, so the builder
must learn to work with the wood, using its irregular curves to best advantage. If this job is done with sensitivity to the
natural grain and form of each log, it can result in a structure that is far too beautiful to be considered a mere shelter
against the elements.
Because a sod igloo is an earth-sheltered dwelling, it's very important that
it be built on a well-drained site, with the depth of the excavation well above the water table. I chose a relatively high
spot in a small clearing where the ground sloped slightly to the south, and began to (laboriously!) dig out a hole that would
eventually measure 3-1/2' X 15' X 18'.
After first removing the top layer of sod in one-foot squares and setting
that future insulation to one side, I got down to the single most difficult part of my task . . . actually excavating the
site. Digging the hole — working alone and by hand — called for about four 20-hour weeks of backbreaking labor,
but finally it was completed . . . and I could get on with the more pleasant task of framing.
I started that job by placing the pilings, beams, and braces as shown in Figs.
1 and 2. The pilings form and support the basic 9' X 12' rectangle that defines the house, and they had to be thick (at least
6" to 8" in diameter), strong, and straight . . . since they bear a lot of weight, including that of two layers of sod and
of up to three feet of settled snow during this area's rough winters. To fasten the beams to the tops of the pilings and the
ridgepole to the beams, I cut simple square notches — in such a way that the log frame could withstand the compressive
forces of the dirt that was applied later — and secured the joints with 10" spikes.
Since part of the front of the igloo was to be left uncovered (it would accommodate
the windows), I knew that the earthen load on the back wall would be much greater than that on the face. And (I figured),
without some extra bracing, the structure would eventually begin to lean away from the greater pressure, becoming unstable.
Similarly, the side of the dwelling opposite the doorway would be subject to extra berming stress. To counter these forces
on the back wall, I installed diagonal braces from the tops of the rear corner pilings to points near the bases of those in
front, butting them against rocks buried below floor level. I braced the wall opposite the door in the same way, except that
in this case the front prop starts below the window. Finally, I ran another support from the midpoint of the ridgepole to
the beam above the window to carry the pressures from the back wall to the front without stressing the poles that would constitute
the structure's roof.
Setting the walls and roof came next. The small trees I selected as my raw
materials were each 4" or 5" thick at the base. (I needed almost 200 of them, but the woods at my building site are so thick
that this depletion did little more than allow a few additional rays of light to reach my clearing.)
First, I cut and trimmed the young conifers and scraped them clean. Then I
began to build my walls, leaning the poles against the frame at a slant of about 4-1/2 inches per foot of height. (I reasoned
that, by doing so, I could use gravity to help hold the earth and sod against the walls . . . and allow the floor's
dimensions to be greater than those of the ceiling.) I hammered each pole deep into the soil, nailed its upper end to the
top beam, and sawed off its excess length. (For the sake of the inside appearance, I placed the poles as close together as
I could, but an occasional gap — even as wide as 6 inches — wouldn't have done any harm, because the whole wall
was sealed off by plastic sheeting later.)
I set the roof poles across the beams and ridgepole, nailing and trimming
them as I had done for the walls. Then I laid the plastic vapor barrier in place and stapled it to the logs (more about that
later) before beginning to build the earth and sod layers that would provide my new home's insulation against the cold.
It might have been quicker and easier to use boards or plywood for my ceiling
and walls. However, the fact that the small trees I cut and peeled were available free-and already too thickly clustered for
continued healthy growthplayed an important part in my choice . . . and so did the aesthetic appeal of the soothing visual
rhythms produced by their irregular rounded shapes and natural wood grains, especially when seen by lamplight.
Indeed, after I'd worked so intimately with earth and trees in the building
of my house, putting an exterior plastic covering over those gleaming shafts of wood felt like sacrilege. The vapor barrier
was necessary to keep the dwelling dry and snug, of course, but I was still glad when it was hidden away beneath the mound
of dirt and sod insulation that left my new home looking like an organic (albeit somewhat traumatized) part of the clearing.
At summer's end — after taking a twomonth break to pick apples and bring
in some much needed cash — I laid a plank floor, hung the door and windows, rigged up a woodstove and chimney, and moved
into my sod igloo just before the first serious snow of the season transformed the Vermont landscape .
. . . WHAT I EXPERIENCED . . .
During the first weeks of winter, small beads of condensation formed on the
plastic sheeting between the poles, and I was afraid that my shelter was going to be damp and cursed with mildew. But as the
earth around the walls began to absorb the heat generated by my stove, the moisture disappeared. At the same time, living
beneath a ceiling made from several feet of insulating soil and snow was proving to make both economic and aesthetic sense.
Inside, I was warm and cozy . . . outside, the sod igloo now really blended into the landscape, looking like nothing so much
as a large snowdrift miraculously puffing a thin trail of smoke.
While I didn't keep a pound-by-pound record of my fuel use during the winter,
I generally spent about two hours every other day in finding, felling, hauling, splitting, and sawing enough wood (by hand)
to keep me very comfortable through even subzero temperatures. In fact, when I sat reading and writing at my table by the
windows on very cold but sunny afternoons, I had to keep the fire banked way down and remove most of my clothing in order
to avoid being overheated. The igloo was always warm and inviting when I returned to it after a crosscountry skiing jaunt,
too, and at night the flickering shadows cast by my lamp along the naturally sculpted planes of beams and braces made me feel
as though I were living in a work of art .
. . . AND WHAT I LEARNED
That first winter in my earth-sheltered dwelling proved the structure to be
a pleasant and practical home regardless of weather conditions outside . . . but if I had it to build over again, there are
a few changes I'd make. While I had no trouble with rot attacking the underground sections of my support pilings, I believe
it would have been prudent to treat the bases with creosote or old motor oil, or to char them as the Japanese do. I'd also
support the beam over the windows with an additional piling (shown as "recommended" in Fig. 2) placed midway across the front
wall. And although my site was well-drained and I experienced no problems with flooding or seepage (even during the height
of the spring thaw), next time I'd take the extra precaution of adding a floor drain to my basic construction plan.
The one serious flaw in my winter home was that the roof tended to leak during
thaws and hard rains. I believe that the major reason for the problem was my obvious mistake in stapling the vapor
barrier to the log roof, thus making holes that permitted water to creep through. But I also think that two sod layers atop
the ceiling are probably not enough . . . especially in this wet climate.
In searching for answers, I found that the past several years have seen the
publication of many good books about earth-sheltered housing. Most of the techniques and materials they call for, however,
are too complicated and expensive to fit in with the simplicity and economy that are the chief advantages of a sod igloo.
Only Mike Oehler's The $50 & Up Underground House Book seemed to offer a reasonable solution to my particular problem.
I've detailed Oehler's roof insulation scheme on the right-hand side of Fig.
2. Mike covered the ceiling material first with building paper and then with 6-mil unstapled black polyurethane sheeting,
maintaining a foot of overlap. Above that "foundation" he laid down four inches of stickless, stoneless, finely sifted earth
. . . yet another layer of plastic . . . four more inches of clean dirt . . . and a topping of sod blocks. Of course,
such a roof would be heavier, more complicated, and somewhat more expensive to build than mine, but I believe that it would
result in a drier home.
On balance, though, my sod igloo was exactly what I wanted (and needed) to
get through the winter. Inexpensive and relatively easy to build, it kept me comfortable and in good health through subzero
cold and spring thaw. When I tally the cost against the rewards, I don't see how I could have chosen any better.
EDITOR'S NOTE: If you're unable to find the manuals mentioned above in local
bookstores or libraries, you'll be glad to know that The $50
& Up Underground House Book can be ordered — for $8.95 plus 95˘ shipping and handling — from Mother's Bookshelf
® , P.O. Box 70, Hendersonville, North Carolina 28791.