Straw bale construction uses baled straw from wheat, oats, barley, rye, rice and other grains in walls covered by stucco. Stucco-covered straw bales offer a thick wall system, which is energy-efficient, durable, natural, healthy, and fire-and pest-resistant. Straw is traditionally a waste product, which farmers do not till under the soil, but sell as animal bedding or landscape supply because of its durable nature. It is important to recognize that straw is the dry plant material or stalk left in the field after a plant has matured, been harvested for seed, and is no longer alive. Hay bales are made from short species of livestock feed grass that is green/alive and are not suitable for this application. Hay is also typically twice the price of straw.

In many areas of the country, straw is also burned in the field, causing severe air quality problems. Building with straw offers environmental benefits in that it (1) avoids the damage caused by burning straw and (2) creates an energy-efficient, healthy and durable wall system.

Two hundred million tons of straw are burned annually in the US. The stability and lack of weathering in straw is not desirable in agriculture but quite desirable in construction. Approximately 10,000 acres of wheat and oats are harvested in the Travis County region each year. Eight to ten acres can supply sufficient straw to build a small house. The best time to obtain straw is at harvest time, May through June, in the Austin area. There are a number of straw bale buildings now located in the Austin area, and local, expert consultation and construction is readily available. Straw bale construction exhibits R-values of roughly R-34. The bale walls achieve a high degree of fire resistance due to the dense packing of bales and to the cover of cement mortar/stucco. Straw in straw bale structures has not shown evidence of insect or vermin infestations. More details are becoming available for working with straw bales (see the General Interest section of Resources). Thorough research is recommended prior to using straw bales for construction.

Also see the Green Building Factsheets for introductions to this and other green building topics.

Any unusual building technology must be evaluated by the code enforcement authorities before approval can be granted. This is typically done by review of another code agency's approval or position on the technology or by review of test data supplied by a reputable independent laboratory. There are straw bale building codes adopted in parts of Arizona (the City of Tucson, Pima County, Pinal County, the Town of Guadalupe), California (State Guidelines and adopted codes in several counties and municipalities), Boulder, Colorado, the State of New Mexico, and our own Austin, Texas. Anyone wishing to receive approval in Austin should follow the local straw bale construction code. The inspections department in other areas can refer to the Green Building Program or the Straw Bale Association of Texas for locations of precedents from building inspection departments.

There are numerous examples of this construction in the Austin regulatory jurisdiction and in the greater Austin area at this time. Building inspection officials will indicate what, if any, test data is needed. Testing is currently being done in Arizona, California and New Mexico. At this time, there are also a number of insurance companies and lending institutions in the Austin area that have given their approval to straw bale construction. Straw bale construction is appropriate for most regions of the country, but good principles of climatic design and construction must always be considered and correctly applied.

History

This technique has been recently revived as an alternative to standard stick-frame construction in order to build highly insulating walls (R-34). The technique was practiced in the plains states in the latter 1800s and early 1900s (mostly in Nebraska). Many of the early structures are still standing and being used. The technique has been applied to homes, farm buildings, schools, commercial buildings, churches, community centers, government buildings, airplane hangars, well houses and more.

Straw is also being used as a building material in sheet materials such as medium-density fiberboard. However, the approach of using bales directly, despite its history, is a new technique from a regulatory standpoint. The City of Austin recently passed a straw bale construction building code which is the fifth code enacted by a governmental body in the United States.

Costs

Building walls with straw bales can be accomplished with the assistance of unskilled labor, aiding in the possibility of reducing the costs of this technique. The cost of straw bales will differ depending on what time of year they are bought. They are cheapest at harvest time versus after the harvest, when they have been stored in a barn. Transportation and handling costs also need to be considered. A rough estimate to consider is $3.50-$4.75 per bale, delivered. Bales must also be protected from getting wet.

It is important to be wary about the marketing of straw bale construction as a very inexpensive method of building. It is roughly similar in costs to standard construction. It is also only the wall system (usually 5-15 percent of the cost of a home), and any building still requires a foundation, plumbing, electrical, roofing, interior walls, flooring, cabinets, landscaping, etc.

Another cost associated with this building method is the type of stucco and its application. A mud plaster taken from site soil, applied by the owner/builder, and maintained by the owner is quite inexpensive, but may take a long time to apply and will require yearly maintenance. Cement stucco applied by a contractor is accomplished quickly and lasts a very long time without any maintenance, but also has significant costs. As with any style of construction, the more labor input by the owner and the less by the contractor, the less costly it will be.

Basic Wall System Types

Two basic styles of straw bale construction have been used: post-and-beam construction with straw bale infill, and structural straw bale construction or "Nebraska" style (the weight of the roof is supported by the bales) .

A post-and-beam style uses the bales as infill within a timber or steel frame structure. The frame adds to the expense in materials and in labor for working around the frame. However, this approach may be desirable as it offers a roof under which to work during construction and it will be more readily accepted by building officials.

A load bearing or "Nebraska" style uses the bales as the structural wall system and usually uses a wood plate (or concrete bond beam) placed on top of the wall to carry the trusses or roof framing. If the bales are firm, there will be very little settling (typically less than 1 inch). Threaded rods through the bales or an exterior wire tie-down system (connecting the foundation and the top plate) firm up the wall and compress it to compensate for any settling concerns. This system may be the easiest and least costly to use but will still require some good planning and probably the assistance of experienced people for consultation

Stacking Bales

Dry bales should be used. Moisture levels in use and in storage should be below 14%. The bales should also be kept dry after construction. Bales are typically stacked in a running bond (similar to bricks) set on a typical slab or on the wood floor of a pier-and-beam foundation. Usually the first course of bales is raised above the floor 1"-4" by sitting on a raised concrete stem wall or on runners (sleepers) of dimensional lumber in order to keep the bales dry in case of flooding. The first course is also usually impaled onto rebar, which is set into the foundation. The bales are then pinned with wood stakes (1x2x36) or bamboo stakes or rebar (#3 or #4) that penetrate at least two bales. Another less popular method uses mortar between bales. A new method uses 4" wide circular columns of concrete bored through the entire height of the wall to hold the bales together as well as provide structural support for the top plate. Even newer systems may eliminate stakes and instead, use bamboo splints on the interior and exterior, which are attached to the bottom and top plate and then tied through the bales to each other.

Bales can be used flat or on edge, but they are best used flat for structural purposes. Bales should be firm and strung tightly with either baling wire or twine. Half bales and whole bales are needed so the bales are staggered when stacked. Bales in Texas usually come with two-wires holding them together, weigh about 50 pounds and are usually 14 inches high, 18 inches wide, and 35-40 inches long (Three-wire bales are 16-17 inches high, 23-24 inches wide, and 42-47 inches long and are typically seen in western states).

Windows

Wood window and door frames are installed during the bale raising and are typically accentuated towards the interior or exterior of the opening, creating a deep well. Care is needed to avoid water entering or collecting in these areas.

Utilities

Utilities can be laid in the walls as they are built, or run in moldings, interior walls, under floors, in the foundation, or in the attic. Professional straw builders tend to stray away from putting plumbing in straw walls due to possible leaks and the ensuing damage. If this is done, make sure to put the plumbing in an additional pipe sleeve that can safely drain any future leak. Electrical wire (Romex) is typically held against the bales by wire pins pushed into the bales (Robert pins). Electrical boxes are typically screwed onto 10"-14" wooden stakes or wedges and then hammered into the bale walls.

Poultry netting is then mounted on both sides of the walls to hold the stucco or plaster. Stucco lath or mesh (diamond lath) is used around windows, doors, and corners for added strength. The wire netting and lath are also typically held against the bales by Robert pins. Two or three coats of stucco (or natural plaster) on the interior and exterior walls finishes the system.

Center for Maximum Potential Building Systems
8604 FM 969
Austin, TX 78724
(512) 928-4786
www.cmpbs.org
Design and consulting

DAWN SouthWest
1039 E. Linden St.
Tuscon, AZ 85719
(520) 624-1673
www.greenbuilder.com/dawn
Resources

Development Center for Appropriate Technology
David Eisenberg
P.O. Box 27513
Tucson, AZ 85726-7513
(520) 624-6628
www.azstarnet.com/~dcat
Consulting, codes, regulation, advocacy

Sustainable Building Coalition
PO Box 49381
Austin, TX 78767-9381
(512) 490-8797
www.greenbuilder.com/sbc
Bi-monthly meetings, lectures, resources

Sustainable Systems Support
P. O. Box 318
Bisbee, AZ 85603
(520) 432-4292
www.bisbeenet.com
Consulting, workshops, videos

Contractors:

Bach Brothers Construction
Craig Bach
16609 Flintrock Rd.
Austin, TX 78738-1608
(512) 261-4777
Construction

Bowerbird Construction
Keith Miller, Owner
P.O. Box 698
Dripping Springs, TX 78620
(512) 858-5395
(512) 858-2061 (fax)
bowerbird@texas.net
Construction, consulting, and workshops

Benjamin C. Obregon, Architect
13429 Overland Pass
Austin, TX 78736
(512) 263-0177
bobregon@austin.rr.com
www.sustainabledesigncenter.com
Design and consulting

Stewardship Inc.
Gayle Borst
2313 West 8th St.
Austin, TX 78703
(512) 478-9033
stewardship@io.com
Design and consulting

Thangmaker Construction
Frank Meyer
904 E. Monroe
Austin, TX 78704
(512) 916-8100
thangmaker@aol.com
www.hometown.aol.com/thangmaker
Construction, consulting, and workshops

Jade Mountain Inc.
P.O. Box 4616
Boulder, CO 80306
(800) 442-1972
www.jademountain.com
"Gringo-Grip" straw bale wall anchor, moisture testers, saws

Zeitgeist Environmental
515 Academy Dr.
Austin, TX 78704
(512) 441-2411
greenhaus@earthlink.net
"Robert pins" for attaching stucco lath to bales

Publications

Build It With Bales , 2 nd version
Steve MacDonald and Matts Myhrmann, 1997

Building of Earth and Straw: Structural Design for Rammed Earth and Straw Bale Architecture
Bruce King P.E.

Guidelines to Straw Bale Construction for the Owner/Builder

Steve Kemble
Sustainable Systems Support
(602) 432-4292

How to Build Straw Bale Landscape and Privacy Walls
Tim Farrant

How to Build Your Elegant Home with Straw Bales
Kemble and Escott
Book and 90 minute video

Plastered Straw Bale Construction
Brainbridge and Steen, 1994

Straw Bale Construction: A Manual for Maritime Regions
Mia Thompson

The Straw Bale House Book
Steen, Steen and Bainbridge, 1994
Chelsea Green Publishing
White River Junction, VT
ISBN 0-930031-71-7

A Straw Bale Portfolio
Bob Lanning

A Straw Bale Primer
Stephen and Orien MacDonald, 1991

Straw Bales as a Building Element
Center for Resourceful Building Technology
(406) 549-7678

Newsletters

"The Last Straw Journal"
HC 66, Box 119
Hillsboro, NM 88042
(505) 895-5400
www.strawhomes.com

Videos

Black Range Films
Star Route 2, Box 119
Kingston, NM 88042
(505) 895-5652
blkrnge@riolink.com
www.strawbalecentral.com