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NEWSFLASH: STRAWBALE MEETS U.S. BUILDING CODES
this article was published in the June 2006 issue of The Last Straw Journal

context
be informed
my experience
related articles

CONTEXT

The bottom line is that yes, using strawbales for non-loadbearing infill walls meets existing building codes for both residential and commercial structures throughout the United States.  Why is this true?  Because building codes are not written to exclude new or alternative construction materials and methods.  Rather, each building code begins with an inclusive statement such as the following from the CABO 95 Preface:

“…there are construction materials and practices other than listed in this code which are adequate for the purposes intended.  These other methods represent either seldom-used systems or performance-type systems which require individual consideration by the professional architect or engineer based on either test data or engineering analysis and are therefore not included herein.”

The intent of building codes to ensure that materials are used safely and suitable, not to limit the use of appropriate materials.  The burden of proof is to demonstrate that an alternative construction method meets the intent of the building code for durability, effectiveness, and safety (including fire resistance).  This means showing how strawbale infill wall systems meet the requirements of the building code for insulation value, flame spread, smoke development rating, and fire rating.  Demonstrating compliance with the building codes is possible thanks to many pioneers that have dedicated time & money to sponsor third-party ASTM (American Society for Testing and Materials) tests.  The results of these tests show that strawbale wall systems not only meet the building code, but in most cases surpass the intent of the code compared to standard stud-and-drywall construction.

BE INFORMED

Several States and Counties throughout the U.S. have adopted building code amendments that specifically address strawbale construction, though most regions do not yet include such provisions.  Obtaining a building permit for strawbale infill in regions without a specific building code is not impossible, but rather entails a non-standard process.  The question is not whether you can get a building permit for infill strawbale, but rather, how to best communicate with local building officials that strawbale is a viable method of construction that meets the existing building code.

David Eisenberg has written extensively and with great eloquence on how to communicate effectively with building officials, and I encourage anyone wanting more detailed information to review his writings on the topic.  I have used the following strategy with success:

1)   Schedule a pre-submittal meeting with the permitting official to communicate your intentions to build with strawbale.  If they are not already familiar with strawbale construction, provide printed information and additional resources.  (Don’t overload with information unless it is requested; like all busy people, building officials are less likely to review a daunting pile.)  Bring to the pre-submittal meeting:

  • drawings of the proposed building

  • an overview of strawbale construction (I use “House of Straw – Strawbale Construction Comes of Age” by the US Dept. of Energy, available at www.eere.energy.gov)

  • copies of ASTM testing data (fire-related ASTM tests are at www.dcat.net)

For the final permit submittal, my experience is that stamped structural drawings greatly facilitate the speed and ease of the permitting process.

2)   Remember that your building official is your ally not your adversary, and has the same goal as you: to ensure that what gets built is safe.  Acknowledge your common interest for occupant wellbeing and safety.  You will create connection instead of confrontation and open a dialog on how to achieve your common goal.

3)  Be informed or hire an advocate that has experience in strawbale construction, including how to build appropriately in your climate.  The building official will generally have more confidence in your project when they know someone on your team fully understands this non-standard construction technique.  At a minimum, be prepared for the following common questions:

  • How does your wall system handle liquid water and vapor?

  • What is the fire rating & smoke development rating of the wall system?

  • Will the strawbale attract pests, such as termites and rodents?

  • What is the insulating value of strawbale?

  • How is electrical and plumbing installed?

MY EXPERIENCE

I have to date not experienced any delays during the permitting process using this method of interaction with building officials.  Increasingly, I find that building officials already possess some level of knowledge about strawbale construction, which was not the case in this region of the country even 5 years ago.

Finally, I would like to address the issue of adopting existing codes and details in different climates.  I design structures in a wet, humid climate with hot summers and cold winters.  However, many of the now-standard strawbale details have mostly developed in arid and temperate climates that are not necessarily durable in this mixed climate.  For example, I do not recommend using rebar inside a strawbale wall in a humid climate, since the cold metal creates an artificial dew point inside the straw wall.  The result is elevated moisture around the rebar, which can lead to rotting the straw over time.  Instead, I recommend external pinning or using materials that are “warm”, such as bamboo.  Similarly, pea gravel at the base creates an artificial dew point, as well as creating a thermal break along the entire base of the wall.  My point is not that the originally developed details are inadequate, but rather that they are specific to an arid climate.  So when adopting codes and details in different regions with different climatic concerns, ensure that what you propose will perform durably in your climate.

RELATED ARTICLES

Overview of Strawbale Construction

Keeping Strawbale
Walls Dry

Down to Earth Design
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