Straw Bale House in the City, Part 1: Designing to Code

Recently, a developer contacted me to build a straw bale “spec” house in the city limits. She had contacted me, because the company I lead had built her family’s high-performance home and she knew my reputation. She also knew that I had drawn a straw bale house before.

The developer asked me what I had learned after dealing with the building officials on the first straw bale house that I had drawn for another client.

Referencing Building Codes for Straw Bale Building

When I drew the first straw bale house, I had spent a considerable amount of time researching straw bale construction and also the building code book’s section on straw bale construction. Michigan’s building code book has an entire chapter dedicated to straw bale construction and is very specific as to what the code allows.

I drew the first straw bale house following the guidelines listed in the code book. The structure that I designed was very similar to a pole barn with 6-by-6-foot treated posts and headers that sat on top of the treated posts. Straw bales would be stacked in between the posts and brick stacked up to the roof line with “pins” every 24 inches.

I made a big mistake on that set of drawings, a mistake that wasn’t a structural mistake; rather, I made one of the walls too tall and that caused the building inspector to require special engineered drawings to ensure that the tall straw bale wall would not blow down. This one wall basically made the project stall out, because there was no one that could speak to the strength of a straw bale wall.

The building official was not refusing to give us a building permit, he just required us to have a long list of items verified and I firmly believe that if I had drawn the house without the tall wall, that we wouldn’t have created a situation that caught the inspectors eye and caused him to raise major concern at what we planned to do.

Revising Straw Bale House Design to City Code

Photo by Adam Bearup

Armed with this knowledge, I went into drawing the straw bale house for the city with the mindset that I had to make sure that every aspect of the drawing coincided with not only the building code, but also with the information that was readily available online. The building officials for the straw bale in the city were not the same group that I dealt with before, and I didn’t know any of the inspectors.

I wasn’t sure how the building inspector would respond after he saw the prints that I handed in with the building permit application. I anxiously awaited his response.

Roof. The house that I designed has a shed roof with a 2/12 pitch. Because of the shallow pitch, I drew a metal roof.

Cost. This project is supposed to cost $100,000 to build, not including the lot, so a metal roof eats up a decent amount of the low budget.

Walls. If the front wall of the house was built entirely of straw bales, that wall would be too tall to meet code, so I reached out to the lumber company to see what they could make for a roof truss to make up the height difference from the front of the house to the back of the house, a difference of over 5 1/2 feet. The trusses were designed so that we could build 8-feet-high walls with the straw bales and that meets the building code without causing any need for concern.

I called out the exact section of the code on Straw bale construction about the lime-based coatings that go on the inside and outside of the bales. I drew this house with 6-by-6 posts with headers and straw bales brick stacked in between the posts. I was certain that this permit was going to get issued!

Discussing Straw Bale with a Buildings Inspector

Several days after I submitted the building permit application, I called the building inspector’s office to see if they had an answer for me yet. The inspector that was assigned to our project was out of the office inspecting, so I left my number and waited for a call back. Later that day, the building inspector called me back and we discussed the straw bale project in great detail.

The building inspector’s first question to me was, “Have you ever built anything like this before?” To which I replied, “No, but I have built just about everything else including earth shelters underground.”

We had lengthy discussions about the building process and I could tell that he had researched like he said he had. He spent hours studying the code book and online resources about straw bale construction and noticed that the prints that I drew and sent to him were spot on with what he had researched. My plan to create a set of plans that were detailed and to the building code had paid off and I could sense that our building permit was just a few questions away.

I was getting excited. I really wanted to build the straw bale house in the city and the conversation was heading in a positive direction. After a few more questions, the building inspector said, “Well, get me a receipt showing that the connection fee for the city water and sewer is paid for and then I will issue you this permit.”

I couldn’t believe it, and before I could say thank you, he added, “I will want inspections of every part of the straw bale construction, moisture testing, pin placement, everything. The liability is just too high for us and for you, I mean, what if the walls rot?”

“No problem”, I said, “What is your lead time for inspections? I want to make sure that you don’t miss anything.” His reply floored me, because I hadn’t even considered this. “No, the inspections would have to be done by a third party.”

My response was, “Do you have anyone that you could recommend?” The building inspector replied, “I don’t know who would even do that sort of inspection, maybe an engineering firm that tests soils and structures.”

I thanked the building inspector for taking the time to research this type of construction so thoroughly and hung up. I sighed and went back to work.

In Part 2, the author determines building a proof of concept is the best path forward and sets out building a test straw bale wall. In Part 3, readers learn the density and moisture considerations that can plague straw-bale construction without proper planning while also covering costs of this project.

Adam D. Bearup is a designer, green builder and farmer, who learned about biodynamic and regenerative farming for a project he built in Northern Michigan, The Earth Shelter Project Michigan. Adam has degrees in marketing and management and a Masters of Science in Green Building.

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