You can huff and puff but you won't blow this house down
FORGET what the Three Little Pigs had to say on the subject. You can indeed build your house with straw. Architect Jon Hammond of Winters, Calif. has done just that. In 1982 he built a studio using hay bales, covered with conventional stucco, for the walls, and so far, this warm-in-winter, cool-in-summer structure is working out just fine. How long it will last, ``only time will tell,'' Mr. Hammond says. But past evidence suggests that the baled-hay walls should stand for at least 60 years, and perhaps twice that long. Excluding labor, and the doors and windows, which Hammond salvaged from other buildings, the prototype studio he built cost less than $1,500.
It's not that Hammond stumbled onto something revolutionary and brand-spanking new in the use of this material. Precedents for this kind of construction stretch back a long way.
Near the turn of the century, for instance, the Sandhills region of northwestern Nebraska was opened up for homesteading. Settlers who came to the largely treeless region quickly found that an accepted alternative to lumber for home construction -- sod building -- was not practical because the soil was loose and sandy.
So, enterprising people that they were, they turned to the one plentiful building material they did have in abundance: straw left over from the wheat, oats, and other grains that they grew.
A decade or so earlier, baling machines had been invented, which turned out a firm, blocklike product that could be laid up much like bricks. When covered with a protective plaster or stucco finish, it would last indefinitely. There is also evidence to suggest that some homes were built of baled tumbleweed.
Proof of the durability of hay-bale construction came in the 1960s, when one of these Sandhills homes was torn down. At the time, farmers were amazed to see nearby cattle leave fresh pasture to graze on the broken walls -- such was the quality of the hay, exposed to the elements for the first time in nearly 60 years.
The way Hammond discovered straw as a building material had a similar sense of serendipity about it.
In 1981 he went to China to design and oversee the building of a hotel. While traveling around he was continually struck by the pleasing design of peasant cottages built of local, inexpensive materials -- stone in one area, clay or bamboo in another. Hammond says he had long felt that the way to go in affordable housing construction was to stay within the constraints of geography and climate rather than trying to overcome them. This meant using locally available materials whenever possible. The China trip confirmed his beliefs.
In California, adobe or fieldstone is the most readily available building materials. But while both are inexpensive for the owner/builder, they tend to be prohibitively expensive in a home built by a contractor. One day, while preparing to mulch his vegetable garden with hay, Hammond was struck by the building-block shape of the unopened bales. ``Why not?'' he mused. At the time he was not aware that his idea had been put into practice by those Nebraska settlers so many decades earlier.
To test his theory, Hammond built a low wall in his garden -- a hay-and-stucco block eight bales long. It held up without the stucco peeling off, and the following year the 18-by-22-foot studio went up.
The building is a post-and-beam structure (three 4-by-4 posts on 9-foot centers in each 22-foot wall) that supports the roof. The straw-and-stucco wall provides a stabilizing effect to the building, but is not required to support the roof.
The hay bales were laid up, bricklike, in staggered formation, and 3-foot rods of rebar (metal rods used to strengthen concrete) were driven through the top of each bale to anchor it to the one below. All told, 100 bales of hay, bought for a dollar apiece, went into the construction. Obviously, you don't have to buy the highest-quality kind of alfalfa hay for construction work, Hammond points out.
To prepare the walls for the plaster, stucco wire was fastened on each side by stapling it to wooden lintels along the top and to -by-2-inch stakes driven in every 16 inches along the base of the wall. Periodically, single strands of wire were threaded carefully through the hay and used to hold the stucco wire firmly against the bales.
In addition, expanded metal/plaster lath was wrapped around each corner and at window openings to support the thicker layer of stucco that would be needed in these regions. A -inch layer of stucco (3 parts sand, 1 part cement) was applied over most of the wall area.
The longevity of the Nebraska buildings suggests that if water can be kept out of the hay bales, the walls should last as long as conventional wooden-stud construction.
To this end, the Hammond studio has a roof overhang that projects out three feet, protecting the wall from all but an occasional driving rain.
To allow any moisture that might get in to readily evaporate out, Hammond stuccoed narrow vents into the topmost row of bales, well under the eaves and sheltered from driving rain.
Before insulating the roof, pouring a permanent concrete floor, or hanging doors and windows, Hammond let the building stand unused for three years.
At the end of this period he chipped away some of the stucco in several places and found no sign of decay in the hay. At that stage he completed the building, converting it into his home studio.
Hammond, who poured 2-foot-wide footings to support his hay-wall building, suggests that a damp-proof layer of heavy tar paper or similar product be laid over the foundations before stacking the bales.
Though he did not do this himself, he sees it as a wise precaution against moisture wicking up through the concrete and into the hay. Another option would be to place the bales on a mud sill of pressure-treated lumber.
With the stucco covering, the walls are more fireproof than conventional stud-wall construction. But it would still be necessary to place a thermal barrier between any wood stove and the wall, as is required in any conventionally built house.
Windows in the thick-walled structure are placed on the outer edge, so no rain will collect on the sills. This produces broad interior sills that can be used as plant niches or for bookstands. Window seats are another option readily adapted to the hay-bale wall.
Hammond built his studio at his farm, where building code requirements are minimal.
He was assured by the local building inspector, however, that as long as the building was structurally sound, there would be no objection to hay bales anywhere in the county, since straw and rice hulls are the most basic ingredient in particle board, commonly used in general house construction.
The excellent insulating qualities of the hay bales, coupled with the heat storage provided by the concrete floor, have produced a studio that stays attractively cool in summer and is readily warmed during the long foggy-weather periods common to winter in that region of California.