Paulina. Building with Earth: A Guide to Flexible-Form Earthbag Construction. Chelsea Green Publishers, 2001. ISBN 1-890123-81-0.
CHAPTER 3
What are Straw Bales?
As bales are the essential building blocks for your home, it is important to know your bales. If you are going to make the right choices, you should understand how bales are made and what qualities to look for.
Speaking of Straw
Rectangular bales dotting the fields in midsummer is a familiar sight to a lot of people. An essential rural icon, a field of bales is often a symbol for wholesome rural ideals. But are those bales straw or hay?
Straw Is Not Hay!
It is common for people to confuse straw with hay. While bales of the two are the same size and shape, they are different substances. Hay refers to any combination of field grasses that are grown to maturity, cut while still relatively green, and baled to use as livestock feed when fresh grasses are not available. High in moisture content, food energy — a full course meal for critters big and small! — and having the potential to sustain microbial activity that can cause rotting and mold, hay is not what you want in your walls. Build your house with straw. Feed the hay to your livestock!
3.1: The seed heads of this summer barley are what the farmer wants to harvest. Once they are removed, the stalks are baled into a great building material.
“I’ll Grind Your Seeds to Make My Bread .…”
Straw, the dried stems of grain-bearing grasses, is harvested as a by-product of cereal grain farming. The nutritious seed head is cut — threshed — from the top of the plant once it is fully mature.With the seed head gone, the stalks are dried and baled.
The most common types of straw are wheat, oats, barely, flax, and rice. All of these are commercially farmed in most parts of the world. But any kind of straw can work, including hemp, spelt, rye, and other specialty grain and seed plants. It is possible to bale and build with almost any fibrous plant stems. As long as the majority of seed heads are removed and the stems are thoroughly dry before baling, anything growing nearby can be baled and used.
Farmers may use their straw as bedding for livestock, and gardeners use straw to mulch crops. But 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,
