Straw Bale Homes Protect Against Fire Where Conventional Homes Fail

Written by Andrew Morrison

house on fireWe have all seen images of the massive fires in southern California. I would first like to send out my sympathy to anyone affected by the flames. I would also like to send out my respect and gratitude for the firefighters who risk their lives and give their all to defend the homes and lives of others. I have considered how to write about this topic over the last few days and I want to be clear that my intention is to support home owners in the affected areas, not judge them or tell them they have “done something wrong.” I want them to know that straw bale homes protect against fire where conventional homes fail. I have included a video at the end of this post which speaks to the fire wall testing data for straw bale walls.

Protecting against fires has long been important to code officials, builders, and home owners alike. None of us want to see our homes go up in flames. None of us want to experience the loss and the grief associated with that loss. Building codes exist to protect homeowners from fires: both minor and catastrophic. Even with those codes in place, we have seen that a well built house can burn to the ground in a matter of minutes. To me, the reason for this is obvious.

A conventional stick framed home is nothing more than a series of chimneys behind a thin layer of fire protection. What many homeowners don’t know is that the majority of the fire protection required by code in a conventional home is in the form of drywall. That’s it! 1/2″ of gypsum board is all that is required to protect you from fire. Once that drywall barrier has been compromised, there is nothing to stop the fire from attacking the structural wood and/or steel framing in your home.
burned down house
Straw bale homes are different. Straw bale houses are known for and have been tested to resist fire by up to three times that of conventional homes. Three times the protection may be the difference between a total loss and a miracle. The photo below shows how a home built of the right materials can survive even amongst completely destroyed homes built to conventional standards. I want to be clear that this photo is not of a straw bale home as I do not have a photo in my possession that shows what I am talking about; however, the data is the same.

A house built with bales has up to three times the fire resistance of a conventionally framed house. The house in the following photo does have one thing in common with straw bale homes: it is plastered. This is the first line of defense for straw bale homes. The 1- 1/4″ of plaster provides far superior resistance to flame than most sidings. Imagine trying to burn your way through that much plaster.
fire resistant house
The second, and often most surprising element of straw bales that increases the fire resistance is the bales themselves. When most people think about straw and how it performs in fire, they think about barn fires, spontaneous combustion, and other fire stories. The fact of the matter is that barn fires are caused by hay that was baled too early with high levels of moisture still in the crop. The fires start when that moisture creates heat by decomposing the hay and then the hay flares from the heat of the decomposition inside the bale. Straw is baled when the crop is dead and dry, usually around 8% moisture content by volume, so no interior decomposition occurs.

Moreover, the bales are so tight, that most of the oxygen has been squeezed out of them. Fire cannot exist without oxygen, so once again the bales have created a form of protection against flame spread. Consider that a bale is like a phone book. If you rip out the pages one by one and light them on fire, they will burn: so will loose straw (although not very well due to the high silica content).

If you hold a lighter under the entire phone book, however, you will likely run out of fuel in the lighter before the book catches fire because there is no oxygen in between the pages to support the flame. The same is true for the baled straw. Now put the two systems together: thick plaster on both sides of the wall and dense, oxygen deprived bales inside. This combination makes for a very resistant wall and one which has a much better chance of survival in fire situations.

Protecting your home from fire in other ways is still important. Be sure to clear brush from around your house, clean out your gutters and under your decks, and so on. There are several sites which offer guidance on how to protect yourself from wildfires. If you live in a fire prone area, I strongly recommend that you complete the steps outlined on those sites.

The above video talks about some relatively recent fire testing on straw bale walls. The results of the testing were very positive and support everything that I have said about straw bale walls and their fire resistance. My want is for people who live in fire prone areas to start getting serious about protecting themselves from fire. Thousands of homes and buildings have been destroyed in the last two weeks by the wild fires in Southern California.

Most of the people who lost their homes will rebuild. I invite them to build with bales instead of building another conventional home. The benefits go beyond fire protection and reach into the world of green construction and healthy homes. But for this conversation, consider the difference between a total loss and a miracle the next time the fires comes blowing through…which they will!

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One area that is not covered by this post is how to protect the extensive often wooden overhangs that are also a feature of most straw bale construction. Yes, this is nitpicking but it is not meant in any way to negate this fine and constructive post. This is a particular concern I have not personally found any good way to address in my own straw bale construction projects in a potential forest fire zone.

For those looking for the actual testing data, the engineers report and the video of the fire testing referred to here, please go to: http://www.ecobuildnetwork.org/strawbale.htm and help support Ecobuildnetwork. They have done more to provide technical support for bale building than anyone around.

All best,
Tony Novelli
Assistant Director
Development Center for Appropriate Technology

I’m very glad you posted this topic because I was about to write you on another matter. How well do you think straw bale houses can stand up to coastal living,as on the South Fork of Long Island (home of “the Hamptons”) with fog, humidity, sea breezes and winds and the occasional hurricane? Here, we are “famous” for shingle houses and McMansions, with little available real estate available to the average person unless the land is 1/2 or 1/4-acre. My town really put the squeeze on locals when it up zoned to 5 acres minimum, two years ago. Do these… Read more »

Mr. Morrison, I am a straw bale contractor living in New Mexico; I have specialized in straw bale houses and walls for approximately 16 years and own a company called Paja Construction, Inc. I’ve built scores of straw bale houses and hundreds of straw bale privacy walls. I just read your article about straw bale houses and fire. Based on my unfortunate experiences with the same, I must say that in my opinion you are somewhat inaccurate about the burnability of straw bale houses. Yes, it is true that lab tests and some field situations conclusively prove the inherent safety… Read more »

Andrew,

The house in your picture which survived the SF fires is made of AAC (Autoclaved Aerated Concrete). We actually looked into using it as an alternative, but were told (in earthquake land) “You couldn’t afford the structural engineering”.

Also, it doesn’t really matter much when the city is forcing us to put in $8,000 worth of fire sprinklers in the house. It won’t burn, but it will probably be ruined by water….

I am building a straw bale house in Carmel Valley, California and have covered a few areas of the bales with OSB plywood by the doors and windows to create a smooth surface. There are studs on either side of the wall. The rest of the bales will be covered with wire and plaster. Do I have to do anything to the bales that are simply covered with OSB , which will then be covered with stucco wire and plaster but thinner coat than the 1.5″ over the bales. I wanted to ask if it is necessary to cover the… Read more »

One other aspect that seems to have been missed is the roofing material itself. I recently moved from B.C. where in 2003 we also had a large number of houses burned in forest fires. Cedar shingle roofs proved to be the Achilles heel for a number of homes. I’m not sure how many of the houses in California were built that way. The advancing firestorm sends out swarms of large embers that land on the roof and begin to catch the roofing material on fire. I don’t know how susceptible to fire asphalt shingles are, but I suspect it’s probably… Read more »

Dear Mr. Morrison: I was thinking the exact same idea about the fire resistance! I am a sixty year old widow, my only daughter got married on December , 2006 with a Navy young man despite his age (25) he already went twice to Iraq! and now he is studying to be a Chaplain; she is pregnant with TWIN BOYS! My life is full of surprises! Anyways…I got a dream, for many years (about 15) since I took a look in a picture of a Straw Bale house…I see so many good things and even I did not get inside… Read more »

I just moved back to Florida. I think we made a mistake and are going back to Tucson, AZ where I first saw a straw bale house and love it so much. Do you know of any one in the Tucson area that makes them and can you get me a number. I hate the damp, humidity here and I have pain Ii didn’t have as bad in Arizona. I believe a straw bale wouldn’t be too damp, or can you build here in Florida? I hate to leave kids and grand babies but health is important, thank you Whitedove

You state the the info will be released in July 2006. Did you mean 2008 or is this an old video?

Hi Andrew, I bought your dvd’s and have been very interested in straw bale construction for many years now. We live on a ranch outside of Ensenada B.C Mex. and on oct 26th 2003 our house and bakery burned down to the ground (Santa Ana winds). We just barely made it out alive (8 of us) except for my grandma, she died in the car while we were escaping (smoke inhalation). Since then we have been slowly rebuilding and just the other day got another scare. I WILL NOT lose everything again. I’m seriously considering finishing my house with straw… Read more »

Dear Andrew Morrison, A Canadian builder, Louis Gagné, got the Canadian Mortgage and Housing Corporation (CMHC) to do fire testing on straw bale houses some years ago. Unfortunately I do not have the exact reference to give you, but I do remember that the test included applied heat of about 1800 degrees F (about 1100C), and that in some 3 hours’ of application, the bales did not burn, and the inner temperature changed only some 60C (or so – sorry I can’t be more precise). If I find the reference, I’ll send it you ( a search didn’t turn it… Read more »

Hi Andrew
Have a look here http://www.compaillons.fr/celles_sur_belle1.html
This “ARCANNE” is involved in safety, buildingcodes, insurance and more in the JURA in France and did the firetest on bales in lab conditions for roof and walls. Temperatures of 900°C on the outside for more than one hour and only after more than 40 minutes there was a slow smoldering inside the bales started!
Only bricks or cement do better

Piet
Netherlands

Great information! I am designing several homes for a project here in Southern California. I am using cargo containers for the structure, with strawbales and a new foam material for the insulation. I want the homes to be as fire safe as one can get. Using the containers for structure gives me a house that is termite, fire, earthquake and windstorm safe. I would like to have others who have tried this to comment. Thanks, Dr. Rich

Andrew, and others, My wife and I recently (April, 2007) completed our straw bale home south of Hot Springs, S.D. We live in Wyoming, so it was really just a get away place for us, and several of our friends. On July 7th there was a lightening strike in the canyon to the southwest of our property. The local firefighters were unable to fight the original fire because of its location, and opted to wait until it came up out of the canyon and try to contain it. When the fire erupted out of the canyon several hours later it… Read more »

Leroy, Sorry to hear about your house burning down. It’s surprising that it did. One thing I wondered is if you had aluminum or steel roll shutters to protect your windows and doors? These are becoming more and more common on houses as anti-theft devices (businesses too) and I wonder if that might have helped to protect your house further. If the fire spontaneously combusted the materials inside your home, perhaps that might have been enough protection to help stop it? I’m not sure, but it’s an idea. When I eventually build my house, I’d like to install them anyway.… Read more »

Leroy,

I just purchased some land near Evanston, Wyoming. Since you indicated you are building a stawbale in Wyoming, I would be interested in learning more about any code issues you have encountered and whether you are building the house yourself or having it contracted. Thanks!

I bring up this point when people have disasters too. I live in Washington and we had so many fires and then we had a horrible wind storm this fall which left GIANT trees landing in homes and cracking right through them. It’s sad, buy I think “well what I they had a cob house!?” 🙁 I want to build a cob house, but I will consider straw bale too. Straw bale will most likely go up faster in construction… But do you think cob is an even more industrious and fire resistant material than straw bale? Thanks!

In 2006 I had to travel to Miami and then wanted to drive to see New Orleans after Katrina. I then planned a drive back to Maryland. I saw 3 listed straw bale structures on this odyssey.* One was in the Florida panhandle about 5 to 10 miles from the coast. Several foot plus diameter trees had been blown down nearby, neighboring houses still had “blue roofs” a year after the hurricane. This house had experienced absolutely NO DAMAGE. With volunteer labor this one bedroom home had been built in the 1980s for less than $20,000. The roof was made… Read more »

For as long as I could remember, I wanted to live in a log home. Then I discovered Straw Bale Homes and saw how much they reminded me of Adobe ones (like Sutter’s Fort the historical one in Sacramento CA). I always was delighted entering the stable or building and without any AC, it would be delightfully cool. I have heard that Straw Bales can have the same effect both in keeping things cool in summer and warm in winter. With the Paradise fire so devastating and the last, I heard in the last few hours only 65% contained, my… Read more »

we need more of them in this world!