Natural Building State Code Adoption Project

Exciting progress is underway in making natural building systems more accessible across the U.S.! 

Recent updates to the International Residential Code now include Cob, Light Straw-Clay, Hemp-Lime (Hempcrete), and (not as recent) Strawbale construction. However, these advancements need your support to be adopted locally. We're launching a coordinated effort to guide stakeholders through the adoption process and advocate for these sustainable practices. 

Join us in this crucial mission to make natural building more widely accessible. 

Why is this important?  

1. High resistance to fire, now a concern through much of the US due to seasonal wildfires. Cob walls earned a 2-hour fire-resistance rating with ASTM E119 tests. Light straw-clay and hemp-lime walls are inherently fire resistant by virtue of their required plaster finishes.
2. Climate beneficial, with low embodied carbon and/or high carbon sequestration of the constituent materials of straw, clay, earth, hemp and lime.
3. Seismic safety, by using established testing protocol such as reverse cyclic in-plane testing and out-of-plane testing in university settings (for cob construction) or by making adjustments to the IRC's lateral force- resisting system requirements by compensating for additional system weight (for light straw-clay and hemp-lime). Prescriptive structural use in Seismic Design Categories A, B, and C, and with an approved engineered design required in SDC D. All non-structural provisions apply when an engineered design is employed. All three appendices were reviewed by and received input from multiple California civil and structural engineers and representatives of FEMA.
4. Ensure safe and proper use of these (and other) building systems through plan check and inspections, especially for citizens who have been known to otherwise build without permits when faced with permitting obstacles.
5. Use of low-cost, locally sourced, rapidly renewable, bio-degradable materials.
6. Hemp-lime (hempcrete) is a burgeoning industry, gaining popularity and use since the cultivation of hemp was legalized in the U.S. in 2018.
7. Removes impediments to greater use of these building systems.

Seismic testing at Quail Springs with CalPoly

Cob blocks ready to be shipped for compressive strength tests 

One of the two walls build in fire testing facility in Texas- Walls received a 2 hour ASTM E119 Fire rating.  

We hope you will join us in this important work! If you are interested in learning more or getting involved, please contact Sasha Rabin at sashasrabin@gmail.com

The appendixes we are advocating for: 

IRC Appendix BJ - Strawbale Construction [formerly Appendix AS] and Appendix BI - Light Straw-Clay Construction [formerly Appendix AR] were first included in the 2015 IRC. That was followed by Appendix BK - Cob Construction (Monolithic Adobe) [formerly Appendix AU],  in the 2021 IRC, and most recently Appendix BL - Hemp-Lime (Hempcrete) Construction  in the 2024 IRC. 

The Nitty Gritty: 

The progress so far is the result of the determined work of a core group of individuals, with contributions from over 100 design and building professionals, academics and researchers experienced in natural building across the U.S. While inclusion of these appendices in the IRC is a huge accomplishment, they do not become enforceable building code until they are adopted by a state or local jurisdiction. 

One key difference between an appendix and the chapters of the IRC is that while the chapters are automatically adopted (often with modification and sometimes exclusions), the appendices must be explicitly adopted and often they are not, unless they receive particular support and advocacy.  

Another challenge is that each state or adopting jurisdiction has a different process, timeline, and entity that oversees code adoption. And while most states adopt state-wide codes, in some states codes are instead adopted by each local jurisdiction (counties, municipalities). 

This endeavor is currently a collaboration between The Cob Research Institute (CRI), Quail Springs, and Earthen Shelter. Our team consists of Anthony Dente, PE, principal at Verdant Structural Engineers in Berkeley, CA, Martin Hammer, architect and lead code author/developer, code consultant David Eisenberg of the Development Center for Appropriate Technology (DCAT), and Sasha Rabin, Natural Building Advocacy Director at Quail Springs. 

Our goal is to create guidelines and written templates, as well as coordinate a team of local stakeholders, and assist them in the process of encouraging their states or local jurisdictions, or those in their region, to adopt these appendices.  Approaching state or local agencies or other governmental bodies without the right information or approach can be detrimental to the adoption of the appendices, and our goal is to support people to know the process and speak the ‘language’ better.