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No. 62, Winter 2014

A Strawbale Residential Building Code for the United States

By Martin HammerDecember 13, 2013May 11th, 2022One Comment
Mark, Martin, David and  Laura with ICC sign

Mark, Martin, David and Laura with ICC sign

October 14, 2013 marked an historic day in the history of strawbale construction and natural building.  A proposed appendix on Strawbale Construction, and a separate appendix on Light Straw-Clay Construction, were approved at the International Code Council (ICC) Final Action Hearings in Atlantic City, New Jersey.  Both appendices will be included in the 2015 International Residential Code (IRC) for one- and two-family dwellings.  (See sidebar regarding the Light Straw-Clay appendix.)
This has far reaching implications, because the IRC is the basis for the Residential Building Code in virtually every jurisdiction in the United States.  In addition to making permitting easier, obtaining financing and insurance through conventional channels is expected to become much easier, because concerns about structural capacity, fire resistance, moisture issues, etc. are clearly addressed in the code
Understanding the IRC and the Strawbale Appendix
One caveat regarding code adoption, is that appendices are not integral to the body of the IRC, and must be explicitly adopted by jurisdictions that adopt the IRC.  But the vast majority are expected to include the Strawbale Construction appendix because it fills a great need.  Also, even if a particular jurisdiction does not adopt the appendix, one could cite it in the national model code. This would carry enormous weight, and the appendix would likely be used as the de facto code for a particular project or jurisdiction.
It is also important to understand the content of the Strawbale Construction appendix. The first two sentences of the appendix set an important frame:
“This appendix provides prescriptive and performance-based requirements for the use of baled straw as a building material. Other methods of strawbale construction shall be subject to approval in accordance with Section 104.11 of the International Residential Code.”
Section 104.11 is the “Alternative materials, design and methods” section of the IRC.  It allows for materials, designs and methods “not specifically prescribed” by the code, where the building official finds they comply “with the intent of the provisions” of the code.  This is the window through which most strawbale buildings in the U.S. have been permitted to date.  This window remains open for variations not clearly covered in the new strawbale appendix, but with the advantage that there is basis and general acceptance of strawbale construction as a system of building by virtue of its presence in the IRC.
David Eisenberg RB473 Testimony

David Eisenberg RB473 Testimony

Limitations . . . and Moving Forward
The appendix does not cover every variation of strawbale construction, although it attempts to be general enough to allow for the many variations of strawbale construction that exist, and even ones that have not yet been attempted.  But like all building codes it contains limitations.  For example it limits strawbale buildings to one-story in height.  It contains prescriptive structural requirements for load-bearing walls, and for seismic and wind design, which fit into the established prescriptive requirements of the IRC.  It does not directly address post and beam systems, which is a common method of strawbale construction.  For a post and beam structure, one would follow wood-frame structural requirements in the body of the IRC, and combine it with strawbale infill per the general requirements in the strawbale appendix.
Most of the restrictions are easily seen as appropriate for the proper use of strawbale construction, whereas others may be viewed as conservative.  Conservative restrictions (for example, one-story) were determined necessary as a means of gaining acceptance in ICC’s approval process.   However, as with all building codes, the appendix is a living document.  It will evolve over time through ICC’s review process every three years.  This includes the primary authors’ intention to propose revisions at the beginning of each 3-year cycle, as well as the ICC’s public process that allows any individual or entity to submit a “code change proposal” for any of its “I-codes”.  (See for the code cycle schedule.)
In a continuing effort to increase acceptance of strawbale construction more broadly, an appendix is expected to be proposed for the International Building Code (IBC). The IBC as a model code governs all structures except one- and two-family dwellings, which are covered by the IRC.  This would create a path to permits for all non-residential structures, and residential structures not covered by the IRC.  A peer review is under way regarding a FEMA P-695 analysis of the seismic performance of plastered straw bale wall systems. This analysis and review is required for new structural systems in the IBC.  This effort is being led by civil engineering professor Mark Aschheim, with support from Santa Clara University, the California Straw Building Association (CASBA) and the Colorado Straw Bale Association (COSBA).
Martin Hammer

Martin Hammer

The lead author of the appendix is California architect Martin Hammer.  Martin, with help from many others, has been working on strawbale codes since 2001, including for the State of California, the International Green Construction Code, and the International Building Code.  Although those efforts did not yield a place in those codes, they were important in the evolution and ultimate success in the IRC.
Invaluable contributions from many strawbale practitioners and experts made the IRC appendix possible.  This includes Kevin Donahue SE, Mark Aschheim PE, Dan Smith, Architect, John Swearingen of Skillful-Means, David Eisenberg of the Development Center for Appropriate Technology (DCAT), and Jane Andersen PE.  Members of the Global Straw Building Network (GSBN) also contributed, including Laura Bartels, Andy Mueller, Bill Steen, Derek Roff, Graeme North, and Jacob Racusin.  Ongoing support from Maurice and Joy Bennett, former directors of CASBA, as well as current director David Arkin, were also vital to the effort.
Of course the fruit of any labor can be traced to its many roots and branches.  Martin Hammer wishes to acknowledge the pioneers of modern straw bale building, especially Matts Myhrman and Judy Knox, and Bill and Athena Steen  He also acknowledges Matts Myhrman and David Eisenberg as authors of the first-ever straw bale code (Tucson – Pima County, Arizona, 1995), the many people involved in testing and research of straw bale building over the last 20 years, and the entire inspiring strawbale building community worldwide.  And with great reverence and gratitude to the original straw bale building pioneers over 130 years ago in the Sand Hills of Nebraska.
The full text of the appendix as it will appear in the 2015 IRC can be downloaded at:
Additional text and illustrations are planned to be included in the “2015 IRC Code and Commentary”
Martin Hammer is an architect in Berkeley, CA, USA.
He can be reached at

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