Understanding CA Building Codes in Relation to Building with Natural Materials
There are literarily 100’s of people that have put massive amounts of time into this work, but I want to appreciate a few individuals who have done a massive amount of the heavy lifting; Martin Hammer, who is the lead author of most of the natural building codes, and Anthony Dente, who is the engineer for most of these codes. They have both traveled across the county many times testifying at hearings to make this all a reality. I also want to thank Art Ludwig, who has been such a important teacher for me in shedding light on the importance of engaging with these systems, and his the very outside the box way of thinking about solutions.
What are my options for rebuilding with natural building methods?
This is the question my inbox is flooded with right now. I am also hearing a lot of people saying that rebuilding with Natural Building methods is illegal in LA. This is not true! Is it easy or accessible? Unfortunately not (YET).
I am also seeing big broad statements about how there is a code now, so it is totally legal and anyone can build with cob. Also, unfortunately, not totally true.
I am going to try to give a breakdown of the current state of the codes and how one would go about rebuilding in LA with natural materials. I don’t claim to be an expert on this, but don’t see anyone else compiling this information, so I’ll give it a try and do my best. Please reach out if you find errors or have anything to add, and I will update it.
What can I build right now in LA?
Below is a whole lot of information diving into codes and permits, but wanted to start with what you can build right now:
If you live in LA county and are interested in starting to build something with these materials right away, here are a few options that dont require building permits:
Example of a 120 sqf cob shed with a cob garden wall in front
-Sheds- Building a shed to store materials or tools with the square footage being under 120 sqf, overhand less than 2 feet and roof under 12 feet high is legal to build without a permit. This is a great way to learn about these materials, as well as create some infrastructure on properties that have just burned to be able to store tools safely. Although you don’t need a building permit, you may been permission from the Department of Regional Planning, or may not. Details here on building sheds.
-Walls- Building fences or walls around ones property has been shown to help limit fire spreading. Even if the wall is short, it can block the spread of flames, as well as the benefit of building a fence out of something non-flamable instead of wood will reduce the combustable materials you are adding to your site. The details of what you are able to build vary from area to area within LA county, but generally you are able to build fences that are 6 feet high without a permit. You may have to get permission from the planning department depending on your specific locations.
The planning department oversees the use of your property, so may have regulations on where you put a structure. For example your property might have setbacks, meaning you need to have a certain amount of space along your property line where you are not supposed to build, or how high a fence can be in a particular locations, but it does not regulate what you build that fence out of. Since these projects I have mentioned do not involve the Building Department (even though they might involve the Planning Department) they are both great ways of working with different earthen building techniques, including cob, adobe, and superadobe, since there is no regulation on the building method or materials.
Are there building codes for Natural Building? YES!
House built by Sasha Rabin at Quail Springs
Technically they are called appendixes, which is often the precursor to them becoming actual codes. Recent (and not so recent) updates to the International Residential Code (IRC) now include:
In the 2015 IRC:
Appendix BJ - Strawbale Construction [formerly Appendix AS]
Appendix BI - Light Straw-Clay Construction [formerly Appendix AR]
In the 2021 IRC:
Appendix BK - Cob Construction (Monolithic Adobe) [formerly Appendix AU]
In the 2024 IRC:
Appendix BL - Hemp-Lime (Hempcrete) Construction in the 2024 IRC.
(the reason for including the previous lettering system is that in some context that is what is still used- just adding to the confusion!)
One thing to note is that these appendixes are just the wall systems. The residential code will dictate the foundations, roofs, etc…
The next step is encouraging individual states to adopt these appendixes, which is proving to be a harder task than we anticipated. 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. Last year myself and a small group of dedicated individuals (all listed at the bottom of this article) launched a coordinated effort to guide stakeholders through the adoption process and advocate for these sustainable practices in their individual states and counties. (More on that here) While the building codes are said to be a process that the public can partake in, the process and language that is needed to participate is often so complex that it is not accessible to an average person.
What is the difference between a code and an appendix?
Appendices to the IRC are expressly optional. Unlike the main body of the code, each appendix must be specifically adopted by a jurisdiction to become a part of its building regulations. The public can influence this process by expressing the need for such a code to their local building department or overseeing state agency. Other natural building systems, including strawbale and light straw-clay, have undergone the same process, first becoming appendices to the IRC, and then being adopted into state or local building codes.
Seismic activity in regards to earthen materials:
When building in CA we can’t underestimate the importance of building safely with our seismic activity in mind. Over the last 100 years or so, our building codes have done a very good job of creating rules and guidelines that have led to a great reduction in building collapse from seismic activity. Unfortunately our codes have not had the foresight, nor do they change quick enough, to address the now much greater risk of urban firestorms. Our systems in place are not agile enough (or forward thinking enough) to adapt to changes as fast as things are changing.
When building with earthen materials, one needs to respect the incredible weight of these walls. Cob weighs about 100 pounds/ cubic foot. Any small piece falling is very very dangerous, and as the walls start to move in the event of an earthquake, the force due to that movement is massive. That being said, these systems can be built in ways that are safe and will withstand seismic activity very well.
The cob code does not require steel reinforcement in what the IRC calls Seismic Design Categories A and B, which encompass about 80% of the U.S.. Steel reinforcing is required for cob walls in Seismic Design Categories C, D and E, and an engineered design is required in Categories D and E. Those categories are found mostly in western states but also around St. Louis and in eastern Tennessee and coastal South Carolina. More on structural elements of cob building can be found in the book Essential Cob Construction.
A quick look at different options: (also see past blog post What is Natural Building for more details about different techniques)
So many ideas and terms are being tossed around right now, and like I have shared in previous posts, yes to all of them! We will need all the different solutions to make any dent in the rebuild. Although all of these methods we talk about are similar in the fact that they are all different methods of building with the same basic natural, minimally processed materials: earth, aggregate and fiber, they differ greatly structurally.
We could put them into two main categories: high mass, generally load bearing earthen materials, and lighter, more insulative wall systems that are generally infill systems with a steel or metal structure supporting the roof. The earthen wall systems, including cob, adobe, super adobe to name a few, are going to be a lot harder to build in the seismic zones in LA. There are very few engineers who work with these materials, and a lot more testing is needed to make this widespread. The other options like strawbale, light clay straw and hempcrete are going to be a lot more accessible options for the seismic design category in LA. And these are great options! Just because a building has a wooden structure does not mean you can’t make it VERY fire resistant. (See below for a link to case studies on strawbale houses in fire events.)
What are my options with the existing codes in place?
(Again, I am focusing on California here, but much of this information is applicable elsewhere.)
The most common and accessible way to currently build with alternative materials is by submitting an Alternative Means and Methods Request (AMMR). (Section 104.11 of the IBC )
An alternative material, design or method of construction shall be approved where the building official finds that the proposed design is satisfactory.
Prior to the adoption of the various natural building appendices, this process has proven to be fairly arduous, and even though the specific appendixes have not been approved in local jurisdictions, they can still be used and pointed to when applying for an AMMR. This is likely the route one would take to rebuild a home lost in the LA fires with any of these methods. There is precedent for almost all of these building methods I have mentioned.
In other counties in CA, mostly in northern CA (but Ventura as well) there are special codes that allow a lot more flexibility if you are an owner builder, and mostly in more rural places. The most common one is in Mendocino called Class K, in Ventura county it is called the Limited Density Rural Dwelling Code.
More on Cob:
Cob wall in process, hands working the material into the cob below
Cob walls with straw-only reinforcing are possible with Appendix U in regions of low seismic risk. In what the IRC calls Seismic Design Categories A and B, which encompass about 80% of the contiguous U.S.. Steel reinforcing is required for cob walls in Seismic Design Categories C, D and E, and an engineered design is required in Categories D and E. LA is design categories D, E and F. For seismic design category F more testing is needed.
Unfortunately cob is going to be a challenging building method to rebuild with at this time, but perhaps this energy, excitement and attention can garner some funding for some of the testing that is needed.
Where to start?
I always encourage people to try their best to understand the building codes in their location. READ THE CODES! It might not make any sense at first, but try to understand it. Call the local building department and ask questions. Be creative, maybe there are some other ways of interpreting the codes then what is generally thought. Go to your local building department and ask questions. If the LA building department starts to get lots of questions about these methods of building, they will start to pay attention.
Make friends with the folks working there. I cant stress this enough. So often we go about these things with an attitude that we are in it to combat the system, rather than just being kind and talking to other humans. Treat them as though they are there to help you. If they have never heard of these things, be patient, non-condescending, and share information. (list of resources at the bottom of this article) I have also included a list of talking points, so you can share accurate information.
Resources:
Helpful Talking Points:
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.
Climate beneficial, with low embodied carbon and/or high carbon sequestration of the constituent materials of straw, clay, earth, hemp and lime.
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.
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.
Use of low-cost, locally sourced, rapidly renewable, bio-degradable materials.
Hemp-lime (hempcrete) is a burgeoning industry, gaining popularity and use since the cultivation of hemp was legalized in the U.S. in 2018.
Removes impediments to greater use of these building systems.
Further reading:
Art Ludwigs website with so much information about fire:
https://oasisdesign.net/shelter/fire/
Article diving deeper into details of the cob code:
https://www.cobcode.org/docs/IRCAppendixU-CobConstruction_Approval&UseOverview_7.15.20.pdf
Article on case studies of Strawbale houses in fire:
State adoption team:
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.