grain production outstrips our current minimal usage of straw; it is largely considered a waste by-product of grain production. In some places, excess straw is burned in the field, contributing seriously to air pollution.
Tiny Trees in Fast-growing Forests
Each stalk of straw resembles a long, thin, hollow tree trunk. The resemblance is more than skin-deep, for trees and straw share a similar chemical structure — cellulose and lignin — and a similar strength and durability. But because of the smaller dimensions, straw grows to maturity in just one season.
All straws vary in their physical properties, and crop quality can also vary depending on weather and soil conditions. Typically, if a type of straw has been grown and stored successfully in your climate, then it will be an appropriate type of straw to use for building, since you will essentially be storing the straw in your walls.
Get to Know Some Straw
Each little tree trunk of straw is remarkably strong. Straw is capable of quickly dulling metal cutting blades and is hard to tear apart by hand. It also resists decomposing quite well, which anyone who has mulched with it will confirm. Pick up a piece of straw — even long dry grass at the edge of your lawn will do — and you’ll be amazed at its strength and resilience. Imagine thousands of these rugged tiny trees packed tightly together to create your building bales.
About Bales
The Harvesting Process
Commercial grain fields are harvested by a combine. This machine cuts the grain stalks close to the ground, then threshes the seed heads. The bare stalks — straw — are deposited on the field in straight lines to await baling.
A baling machine is pulled over the field, sweeping the lines of straw up into a chamber where a mechanical plunger compacts the loose straw into thin square flakes. (You’ll hear a lot about flakes later on.) A number of these flakes are pressed together in the chamber and mechanically tied with twine into a bale. The bale is either redeposited onto the field or kicked into a trailing wagon. Different baling machines produce bales of differing quality. Even bale quality from the same machine can vary dramatically, depending on the sharpness of the cutting blades and the adjustments made for the tightness of the strings.
How to Find Bales
You can’t order bales from the local construction supply yard, unlike most other building supplies — not yet, anyway! So, when it comes to finding your bales, you’re on your own. However, anywhere grain is harvested, so is straw. Chances are good that there is straw within a reasonable distance of your chosen building site, even if the site is urban. Many cities are built near or on prime farmland, and the farmers who have maintained their land near these areas are often producing some grain crops. But how to find the right farmer with the right bales?
Other Baled Stuff
Bales of straw are not the only way to create energy-efficient buildings out of useful by-products. Very successful structures have been created using bales of boxboard, waxed cardboard, shredded paper, nonrecyclable plastics, and car tires. Straw, too, comes in other baled forms, including jumbo bales (3-by-3-by-9 feet and 4-by-4-by-12 feet) and super-compressed bales (jumbo bales squished down to regular bale size).
Straw bale building is all about using abundant resources available locally, and sometimes the above baled materials may just meet these intentions better than the straw bales we describe. In some cases, straw bales can be used in conjunction with other baled wastes. If you choose any of these materials, know that there are people who already have experience with them, and do as much research as possible. You’ll find that many of the concepts and construction details covered in this book will apply to these other baled materials.
3.2a-f: Straw is not the only baled “waste” that can be used to build. Buildings have been created using bales of boxboard, shredded paper, non-recycleable plastic, waste agricultural and lumber fibres (under the name Stranbloc), used car tires and waxed cardboard.
— Chris Magwood The Last Straw, no. 42, focused on many of the above alternative baled materials. You can find TLS online at <www.thelaststraw.org>.
Go Where the Farmers Are
You can look for bales in several ways. A drive along some rural roads where active farming is taking place will show you who is growing grain, and as often as not you’ll see a sign at the end of a driveway advertising straw and hay for sale. You can also approach a local feed mill, farmers’ co-op, or grain elevator. They will know who is growing grain and might be able to put you in contact with an appropriate source. They may be willing to broker the sale for you, although they will add a percentage to the cost for providing the service. Farmers’ markets, agricultural fairs, farm equipment sales centers, or any other places that farmers frequent can be good places to start. An advertisement in a few small town newspapers or wanted flyers can also put you in direct contact with farmers who have bales. As bale building grows in popularity, regional bale building associations are formed. These groups can put you in touch with good bale suppliers, as can bale home owners, designers, and builders. The Last Straw’s annual Resource Guide lists bale suppliers by state and province.
Old Bales, New Bales, No Bales
You can use bales that have been in storage from previous harvests, or you can preorder your bales from the current grain harvest. Remember that bales are an agricultural product and therefore are susceptible to fluctuations in weather, crop prices, and demand. There are both lean and abundant bale years. Where grain production is modest in scale, farmers will sometimes reserve their entire harvest for their own use. For this reason, it is best to source your bales as early as possible.
Round Bales Don’t Work
In recent years, baling machines that create large, round bales have come into favor with many farmers. However, you can’t build with round bales. You’ll have to specify that you need square bales. If contacted prior to harvest, some farmers who currently bale round might use their old square baler in order to make the sale to you. It can sometimes be frustrating to see literally tons of straw at hand but in a form you can’t use. Be persistent — somebody out there has square bales for you.
Plastered round bales may perhaps make for an interesting way to create structural columns, but nobody to our knowledge has tried this ... yet!
Two-string versus Three-string Bales
Much of the pioneering work in reviving straw bale construction was done in the southwestern United States. There, large three-string bales are common. In areas of small-scale grain farming, two-string bales are the norm. Both are suitable for building purposes; the kind you use will be determined by the baling standard in your local area.
The Three Bale Basics
When faced with a towering mound of hundreds or thousands of bales, it’s good to know what to look for. You have three basic concerns: tightness, dryness, and size. Before making your purchase, be sure you are satisfied on all three counts.
Tightness
You want your bales tight. Bales can be tied with polypropylene string, sisal twine, or metal wire. Any of these options is fine. It is the solidity of a straw bale that allows it to be used as a building material, and that solidity — or lack thereof — is a direct result of how tightly the bale has been tied. A farmer can adjust the baling machine to vary the tightness. Really tight bales use less twine or wire to bale an