Please Support the Proposed Straw Bale Building Code

Written by Andrew Morrison

straw bale building code IRCI recently received a call for support from my friends at CASBA, the California Straw Building Association, for the proposed straw bale building code which is being submitted for consideration to the International Residential Code (IRC). I am a big supporter of straw bale codes, and of building codes in general.

Many people think that unusual as they consider codes to be simply the government’s way of extorting money from home builders and home owners. I disagree, for the most part. I’m sure there are codes that step well beyond the bounds of necessity; however, most are in place to protect the people living in the homes they build.

I have seen MANY owner/builders create incredibly unsafe homes because they simply did not understand the risks involved in building and the huge weights and forces that are involved in the construction of a home. I believe that codes do a good job of protecting people whom would otherwise not even know what to look out for.

On another note, more specific to straw bale construction, codes are a huge ally for those of us wanting to build with bales. Inclusion in the IRC  would make getting building approval so much easier anywhere that those codes are enforced. After all, if it is in the code book and your project design meets those code requirements, there is nothing to stop you from getting an approval. It won’t matter if your local building inspector has never heard of straw bale construction or if they think it’s stupid. It won’t be up to them anymore!

I’ve included a PDF version of the draft code for you to review and a call to action to help support the effort to get this code included in the IRC. I’ve also included some details from CASBA entitled “Why is it important to have a straw bale code in the IRC?” I hope you will take the time to get involved and help move straw bale construction forward.



Proposed Straw Bale Code for IRC (revised 2.27.13)


Why is it important to have a straw bale building code in the IRC and IBC? (The current Straw Bale Construction proposal is for the IRC, which applies to one- and two-family dwellings only.  A future proposal for the IBC, which applies to all occupancies, is in development.)

A: A straw bale construction section in the International Building Code (IBC) and the International Residential Code (IRC) would greatly benefit designers, builders, building officials, owners and inhabitants! How?

Streamlined Permit and Inspection Process. Virtually all jurisdictions (States, Counties, and Cities) in the United States use the IBC and IRC as the basis for their building codes, and most have no straw bale code. Permitting and inspecting a straw bale project in these jurisdictions can be an ordeal, especially for the first straw bale project in that jurisdiction, or if previous projects had problems. Including uniform, well-­‐developed, and comprehensive straw bale construction provisions in the IBC and IRC would put straw bale wall systems on a national stage and greatly reduce these barriers and delays.

Introduce Current Best Practices. All existing straw bale codes (3 states, 7 cities and counties) are based on the first two such codes, developed in 1995; Tucson-­‐Pima County, Arizona and the State of New Mexico. While groundbreaking at the time, the existing codes are now seen as too restrictive or not restrictive enough, and in some cases don’t address important issues. For example, New Mexico’s straw bale code does not allow load-­‐bearing systems, California’s code allows straw bale shear walls but provides almost no detail (creating potentially unsafe buildings), and none of the existing codes address numerous important structural and moisture-­‐ related issues.

Seventeen years have passed; testing, research, and the design and construction of many hundreds of straw bale buildings has significantly advanced our knowledge and understanding, raising the minimum standards bar. The new proposed code reflects this.

Ensure Regional Variation and Periodic Revisions to Reflect New Best Practices. Code adoption would properly regulate straw bale construction, with a set of standards that assure safe and durable buildings while allowing flexibility for the variations of straw bale construction. Once in place, the straw bale provisions would undergo the same public code change proposal process that each model code undergoes every 3 years, allowing further development and revision that improve minimum standards.

Legitimacy and Wider Acceptance. A straw bale construction section in the IBC and the IRC would legitimize straw bale construction in every realm that relates to buildings: architecture and engineering communities, planning and building departments, the insurance industry, and the financial loan industry. Companies from the latter two have often been known to deny coverage or service after learning that a home has been constructed with straw bales, sometimes citing that “it is not in the building codes.”

Increase Exposure for Natural Building. Inclusion in the IBC and IRC would not only make it easier to build with straw bales, it would also pave the way for other natural building materials and systems that deserve a place in the building codes, such as straw-­‐clay, cob, rammed earth, and bamboo.

Want to learn more about straw bale houses and how to build one? Want to do so for FREE? Sign up for our totally free 16 Day Straw Bale eCourse! Find out more HERE.

31 Responses

  1. Thank you for always being an advocate for straw bale building and getting the word out to others!

    I hope you don’t mind me sharing more information, but “the final proposal will be posted at on March 11, 2013″ according to the following website, which also has the draft proposal with the supporting documentation/research posted:

    And this website mentions information about either attending or tuning in by webcast in April/May for the Fire Resistance hearings, if you are interested in seeing how this whole process works getting a code change to happen:

    So happy to know that there is a possibility of wider acceptance for straw bale by 2015!

  2. I believe you would have to have a copy of the code to reference the parts not directly listed within this section. Those are sold as both hard and on line copies, but are not available for free anywhere that I know of. I imagine a Google search will get you to the spot where you can buy a copy. If you plan to build, it’s good to have and get comfortable with the code in advance of your build anyway.

  3. Next week, I will present the proposed codes to the agency and department heads that are directly responsible for all fire, electrical, and building codes falling within the jurisdiction of the State of Wyoming.

  4. Congratulations!

    I am curious about the role of the UBC in these proposals. Specifically, will the UBC “accept”, amend, reject or ignore the IRC and IBC proposals? And, most importantly, how are the states going to support and implement these proposals?

    Thank you and saludos,

  5. This is outstanding news and a major development.
    So many municipal building departments generally put the binders on alternative construction. A definite step in the right direction. Congratulations! And looking forward to learning more as available. Thanks!!

  6. To begin, let me acknowledge that I have not yet read the current straw bale construction code proposal (I have read what I expect is a much earlier version of this proposal back in 2006), but wanted to get an initial reply out quickly.
    I think it is important to know that all model building codes (those that serve as models for adoption by jurisdictions throughout the nation) have always had a section allowing for the consideration of alternative materials and construction systems. Having said this, as an architect, I am intensely and particularly interested in and excited about the straw bale code section development effort.
    Essential to the development of this straw bale code section, I do have one important underlying observation.
    Code sections are typically conceived as one of two types – performance or prescriptive.
    Performance language will tell the reader the technical expectations and standards the type of construction system must meet, typified by quantifications of calculable strength, fire resistance, R-values, etc.. This allows the code user to design – or invent – with whatever arrangement and use of whatever materials works within the constraints of these standards, to achieve a safe result. Prescriptive language will tell (prescribe to) the reader exactly what parts and pieces to use and how to put them together within the context of preconceived (prescribed) building construction systems of selected well-known materials, handling issues like strength with limited use devices such as safe span tables whenever appropriate and possible.
    At the very least, the code section must be performance based, so that prescriptive standards ued for constructing safely in a technically challenging location are not needlessly – and expensively – imposed on a jurisdiction with far less demanding conditions, a risk that runs rampant in prescriptive-only codes.
    The best code addressing straw bale construction will include both types of sections – performance and prescriptive. As a code official once told me:
    “I don’t have the technical background of an architect or engineer.” (this is true of most code officials – they do not typically have the technical understanding to do the kind of creative problem solving with it’s technical analysis and calculations that a performance section invites) “If I tell someone to do something as prescribed in the code, it will, with a fair degree of frequency, be a more over-built and expensive solution, for me to feel assured that issues of safety are fully addressed. With her/his technical analytical skills, an architect or engineer can most often provide a more focused and cost-effective solution to many code issues.”
    A performance code allows for a much more targeted and affordable solution, my constant and optimum goal.
    This is not an advertising ploy on my part, but a simple statement of fact concerning skill sets. When I review the building code – an often complicated and confusing document – I do not hesitate to counsel with my building official, because he often knows his way around this document better than I … I need his understanding of the code to more knowledgeably proceed.
    The same is true of assessing construction in the field, especially less familiar approaches as presented by straw bale construction. I consult with contractors all the time, because they are the ones who will deal with the practical issues presented by whatever I design.

  7. This is great Andrew, thanks for keeping us informed!

    My only question on it is about vapor retarders on the interior of exterior exposed bale walls in zone 5 and below. Have you found them to be necessary in projects in those zones? I’m in 6A so I can squeak past (assuming this recommendation is accepted) but I’m curious as I know a number of folks in zone 5 that would love to build a straw bale home.

    Lastly do you know if there are any vapor retarders that are made of natural materials which could be applied there?

    Thanks again!

  8. As a professional straw bale home builder I disagree with this codes required 1 inch of plaster. For a sloppy owner builder with wavy walls, 1 inch might be good but for a professional that can make a plumb flat wall, 1 inch is too much plaster and added expense. Make it thinner. I have never used a moisture meter & don’t own one and also would like to remove that requirement.

  9. All good questions Rolando. Here is what I have learned.

    The UBC (Uniform Building Code) no longer exists. It and the two other regional model building codes in the U.S. were replaced by the International Building Code (IBC) in 2000. The IBC and IRC (International Residential Code) are the two model building codes used as the basis for the building codes in virtually every jurisdiction in the United States (states, cities, and counties). The Strawbale Construction proposal for the IRC is as an appendix. Appendices do not automatically accompany the body of the IRC when a jurisdiction adopts the IRC as its residential code. An appendix must be explicitly included. However, it is likely that many jurisdictions would adopt the proposed Strawbale Construction appendix, if the appendix is approved by the IRC Committee during public hearings in April. There is a real hunger for a strawbale building code in many jurisdiction across the US. There are only a handful of stawbale building codes in place in the U.S., and most are derived from the first such code created in Arizona in 1995, and so they are relatively undeveloped and in some ways obsolete.

  10. I would disagree with both points here Check. I have been building with bales for almost twenty years and have found a moisture meter to be a very important tool. There have been times when bales in the wall have been questionable after a freak rain shower and being able to ensure they are dry before moving forward with the rest of the job was very important. I also use the meter to randomly test bales as they come onto the job site to make sure that moisture levels are acceptable. Considering that a good one cost only a couple hundred dollars, as a professional, it is a minor cost and as a homeowner, it is great for peace of mind.

    In terms of the plaster, I think a minimum of 1″ is very important. I have seen bale homes with much thinner plaster have trouble over time with minor impacts (basketballs, lacrosse balls, etc.) that would not have been an issue with thicker plaster. Keep in mind that natural plasters like lime and clay also require slightly more thickness to gain the strength they need and that cement based plasters are not a good idea for bale structures on MANY levels. Furthermore, the plaster (if earthen or clay) acts as part of the moisture control system for the home through its hygroscopic properties. Thinner plaster does not provide the same values. Finally, the plaster skins are part of the structural system in many straw bale homes. The use of mesh and/or thin shear strapping is allowed precisely because the plaster adds strength to the wall system. A thin coat of plaster will not provide the same ratings for the wall. This would mean more expense in structural systems which could end up a wash in terms of cost savings, especially when added to the other areas of concern (moisture prevention and long term durability).

  11. I too am not a fan of the vapor retarder on bale structures; however, I don’t mind them nearly as much on the interior face of a wall and can actually see how that would be helpful. I have typically made up the need for this with thicker plaster on the interior to slow vapor movement, but can see that a specific retarder may be even better in some situations. I imagine that there are natural materials that could be used. I wonder if linseed oil would be good enough for the proposed code, as an example.

  12. I would assume that a SB wall vapor retarder could be:

    1. a quality/characteristic(s) inherent within the particular plaster mixture/ingredients recipe
    2. an appropriately located and applied finish surface coating
    3. a vapor retarder film attached/positioned appropriately within the wall section

  13. I have been building with bales since 1996. As far as I know we built the first class 1 residential building in Australia, using a modified version of the Clifornian code, which local officials use still. Before the roof was on we had 128mm of rain on the first coated walls. Moisture levels in bales were over 28%. THe bales dried out, through the stucco, over about two months of meditteranean weather, and are still in perfect condition. DOn’t get too hung up on moisture levels!

  14. An important element is missing from the code: lime stuccos are vulnerable to streaming water. Eave specificiation should be part of the code, as should some specificiaton of the number of down pipes, to avoid wind blown water from overflowing gutters hitting the walls.
    We have lime-washed lime stucco walls facing wind driven rain (ave 1000mm a year) that are now 17 years old in perfect condition, once we tripled the number of down pipes..

  15. So Andrew, does any of this draft proposal go against what you have put forward in your recently published, “A modern look at strawbale construction”?

    Also wondering why bales on edge were defined as having R2/inch while bales laid flat are only R1.3/inch? Obviously this does not really affect the building code, but I don’t understand why there would be a R difference.

  16. If the climate is right to dry them out, they will dry; however, I have seen homes here in the US get wet and stay wet. I think having a moisture meter available to check bales is a great idea. I personally would not finish a house that had bales with moisture levels consistently over 20%. I would wait to see them dry out before progressing with the work. Not a good situation to be in for sure, but I would not want to take the risk. I hear what you are saying Warwick and yet if there is one area of concern to “get hung up on” in straw bale construction, I would suggest that moisture levels would be it. 🙂

  17. Ken, Not that I am aware of. In fact, I think this code is in support of what I have been teaching and building for many years. I am not in agreement with the R-values at all. If a bale wall is actually rated at R-1.3/inch, then I would suggest it is not worth the extra effort if you are looking for a super insulated home. Consider that this would place a typical 2-string bale wall at only R-23.4. I simply cannot sign off on that since the buildings I have built over the years are SO much more insulated than conventional construction and the conventional walls in my area are rated at R-21. There is just no way that my clients could be paying 75% less on their heating and cooling bills if the improvement in R-value was only by R-2.4. I just don’t believe it, personally. The reason that on edge gets a better rating than flat bales has to do with the orientation of the straw. I still prefer building with bales laid flat, by far.

  18. Here’s a suggested letter to your editor that Barbara, a straw bale enthusiast, has drafted and asked me to share. Please feel free to share it, edit it to meet your needs, and use it.

    Dear Editor,

    As a prospective Straw bale home builder I am excited to hear that the California Straw Building Association has assembled a Strawbale Code Task Force of experienced strawbale building practitioners who have written a proposed strawbale building code that if approved, would make getting building plans approved and permits issued a much easier process. Now that the proposed Appendix on Strawbale Construction for the International Residential Code (IRC) is complete, the next step is public hearings in front of the IRC Committee at the end of April, 2013 in Dallas, TX. Participation in those hearings will entail some expense on the part of CASBA and that’s where you can help. We are not asking for a large financial commitment on your part, we are simply asking if you could spare two Latte’s a week for a month or $20.00. Each $20.00 they receive will help the SB Code Task Force have the financial means to appear and testify on behalf of the proposal at IRC hearings. Your financial help will also help ensure that these codes become an industry standard that all builders must follow so that all straw bale buildings are safe, durable, and energy efficient to live in. You may make your contribution either by snail mail to:

    P.O. Box 1293
    Angels Camp, CA 95222-1293

    Be sure to make a note on the bottom of the check that this is for the campaign to get uniform Straw bale Building Codes or you may go on their website at and make a contribution to this project via Pay Pal.

    Sincerely Yours,

  19. I agree that #3 is an option to avoid. Conceptually, it can work, but mandates too many details to be cost effective.

    One possible solution to #3, which I would endeavor to avoid, is to include as part of the overall wall section, in addition to the SB wall element plastered on each face, a wall frame with vapor retarder immediately behind the interior drywall room wall finish. I had a client insist on this once. I don’t like it; too complicated, overbuilt/wasteful, and not accepting of the technical capabilities and natural attractiveness of direct exposed SB construction … but it is a solution, just not a desirable one.

  20. Sorry – accidentally brushed against/bumped my keyboard.

    Your citation of plaster finish thickness as a vapor retarder design variable is important. Thanks for the reminder, Andrew.

    Your thoughtful, observant and careful approach to your work is greatly appreciated. That’s why I learn and use so much from your videos.

  21. We live in East Tennessee near Knoxville. We would like to build with straw bales, but I don’t think the codes allow it in our area, as of yet. Does anyone know if I am wrong about this?

  22. I would ask if they have a provision for alternative dwellings, including straw bale. If they don’t, ask if they would approve a SB building if it is stamped by a licensed engineer.

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