Hay Houses Are NOT Straw Bale Houses: Why it Matters So Much

Written By Andrew Morrison
October 29, 2007

tall stack of straw balesHere is a quick primer on the subject sparked by the following email I recently received. Thanks Josh for the question. This may be obvious to some, but I am no longer surprised by how many people have this very same question. I often hear people use the wrong name for this technology. I hear them talk about hay bale construction or strawbail. The misspelling I can deal with, but the inclusion of hay in the idea of home construction is a problem. It’s straw bale houses, not hay bale homes.

In fact, I even heard a builder, claiming to be a straw bale builder, describe his model “hay bale house” when I spoke to him at his booth at the Green Building Expo in San Francisco last year! YIKES!!! I hope that the builders out there know the difference and understand the importance of working with straw. For those many others who have the same question, here’s the breakdown. Actually, here’s the original email question first, then the breakdown.

Josh wrote:
I’m sorry to ask such a simple question but I would really appreciate it if you would explain (on your blog or in a reply email to me) why exactly you cannot use hay to build with. I have ready access to a LOT of hay that is the same price or cheaper then straw in my area. I would like to use some to build a few small structures but I cannot seem to find much information at all about hay. I have read the available information and thus have had some very simple answers but I’m curious if you would provide a relatively thorough answer to the hay vs straw debate. I need it cleared up so I can share the information myself! Thank you very much! btw – I’m subscribed to your blog and love it!

Here’s my response:
Hay bales are a food source. That is the first and perhaps most important difference. Hay is actually a plant that is cut when it is alive and full of grain. The purpose of the hay is to feed animals. Straw, on the other hand, is simply the stalks of standing plants that contain no grain. The grain is harvested from the plants by a machine that cuts it off of the stalk.

The grain is then removed from the field and the stalks are left to die, standing. Once they are totally dead and mostly devoid of moisture, they are cut, raked, and baled. The baled straw has multiple uses. It can be used as animal bedding, erosion control, home building, and more. One thing it is not used for is food. So, the first question to consider is: do you want to build your house out of a food source or something that will not be eaten? I prefer the latter myself.

The next point to be considered is the moisture content of the bales. Pretend that the whole food source thing didn’t matter, just for now. When hay is cut, it is a live plant. That means it has moisture in the entire plant. It is left to dry on the field for a short time and then raked and baled. In that time, some of the moisture leaves the hay, allowing it to be baled without decomposing. We have all heard of bales spontaneously combusting, right?

Well, this is due to bales having too much moisture in them. They start to decompose on the inside and that creates heat. That heat increases as the decomposition process increases (cyclically at this point) and then the bales burst into flames from excessive heat. This is a situation where there is obviously too much moisture, yes, but it proves the point I am making in a dramatic fashion. Straw bales have very little moisture content in them when they are baled.

This is another difference in material. The lower the moisture content, the less chance of damage to the bales once in the house by either mold or fire from decomposition. In fact, decomposition and mold growth cannot happen in the straw as long as the moisture content is kept below 20%. That is quite high by the way. Most of the bales I use register around 8-9% moisture content to give you an idea.

Finally, the inclusion of the moisture and the seeds can cause something else within the structure that is neither fire nor food: growth! I have seen cob walls where the straw used in the mix had a lot of seed material wrapped up in it. Two days after the plaster was applied, the entire wall started to grow grass!

The owners thought it funny, which it was at least to look at; however, this was indicative of a big problem: they had seeds in their walls. This can attract all kinds of pests from mice to cows. In the cob, it was less of a problem but in a bale wall, it could be a disaster.

So, no food, low moisture content, no growth is what makes straw the ideal product. As a great bumper sticker I bought from CASBA (the California Straw Building Association) a few years ago reads: “Hay is for Horses. Straw is for Houses.” I couldn’t say it better myself!

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.

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67 Responses

  1. Thank you so much! I am now very well informed about the difference in choice. I do of course have quite a bit of hay for our horses and that is precisely where it will continue to go. To the horses. A sod roof would be pretty cool but I’m not so sure the wife wants grass coming out of the walls!

    Thanks again for clearing this up for me. Have a beer/lager/coffee on me!

  2. I know well the difference between hay and straw, but what I don’t know is the preferable TYPE of straw! Someone told me tha Oat Straw is the best choice and I see you like the organic Oat Mkeal Stout, but what about wheat steaw or barley straw? Can these types of straw be used also? Does one have better insulating properties than the others? I assume the bigger the airspace within the stalk would be the deciding factor but have never seen or read about this variable. Thanks for all the great information, Yours in the Green Zone, Tommani R Sandoz

  3. Tommani,
    I believe that the best bales are those that are locally available to you, as long as they are dense, dry, and uniform in shape. Wheat, barley, oat, rice, hemp, cardboard…anything that can meet the requirements for density, moisture, and shape will work fine.

  4. Andrew,
    We are putting some great straw in our walls now but every once in awhile we run into a bale with what appears to be some dried grass in it. Those bales appear green in color here and there, within the obvious straw. Is this an issue? Should we avoid those bales and remove the ones that got put in the wall before we plaster?

  5. If you can easily remove the bales with the obvious grass, I would. I would also not use any with green grass in them moving forward. It will likely not be a problem, but why take the risk? Good catch!

  6. Andrew, we have access to hay that is clean, but to old to be used for feed. I can get it for much less than straw. Local straw dealers charge more than for hay. The hay I am describing comes from costal bermuda, which is a very course grass that produces no seed, as it is sterile. Not moldy and very dry from many years in the cover of a closed barn. Why would it not be usable?

  7. I am looking into building a Strawbale house in North Texas and am concerned about ants, fire ants especially. Will they be a problem?

  8. Hello, I was very happy to discover your website today and would like a bit of advice if possible. I am going to have a wooden house built on my land in France. The builder suggested using loose straw as wall and floor insulation. I’ve read some comments from someone on another website who did that it turned into somewhat of a problem both in terms of time and money spent. Also he said that plasterboard had to be used to meet fire regulations (in the UK) and the straw had to be boxed. Any ideas or suggestions?

    Many thanks,
    Jane

  9. Hi Jane. I would recommend against using loose straw in the walls and floor as it is not the best insulation per cm available and therefore would likely end up being a waste of effort and money. I would suggest cotton insulation if you are trying to stay green. Loose straw is a fire risk and has a relatively low R-value per cm.

  10. Hello Andrew,

    Thanks for your helpful and speedy response. I am a real novice in this field. Could you give me an idea of the cost of cotton insulation and in what application form it comes? Is it appropriate for roof, floor amd wall insulation? I’ve never heard of it being used here in France but of course that doesn’t mean it isn’t.

  11. This is actually so interesting!
    I have a college assignment on ‘hay bale construction’ and couldn’t understand why i could only find info on straw bale… hmmm… seems colleges also make mistakes – and that is scary!

  12. You see the “square” and the hugh “round” thingys in the fields after harvest. Is one more for straw than for hay? Thanks

    1. It depends on what’s harvested. The large round bales can be either hay or straw. It’s best to ask the farmer directly. Either way, you want smaller bales, so start by finding a good local source of 2 string or 3 string bales. You can ask your farmer supply store for leads or go straight to the source by watching fields as they bale and speaking with the farmer directly. I prefer the second, more direct option.

  13. Do you know of any architects or engineers in the Upstate South Carolina/Western North Carolina region who may have experience working with straw bales? I cannot get a building permit without one, and so far I haven’t been able to find one.

    1. I don’t of hand. I’d suggest you contact the folks on the links below as they have completed homes in South and North Carolina and could have some information that will help you. Short of that, you can contact Chris Keefe ([email protected]) and see if he can help you as a designer. He has engineering connections and lots of SB design experience.

      South Carolina: http://sbregistry.greenbuilder.com/search.straw?lcou=United%20States&lsta=SC

      North Carolina: http://sbregistry.greenbuilder.com/search.straw?lcou=United%20States&lsta=NC

  14. 1) Wonderful to hear your site on Straw Bale homes.

    2) VERY IMPORTANT, PLEASE INCLUDE THIS TO EVERYONE YOU TALK TO ABOUT STRAW BALE HOMES.
    (KISSING BUG DISEASE )( Triatominae) (CHAGAS DISEASE )(American trypanosomiasis) ( Caused by the flagellate protozoan Trypanosoma cruzi. )

    This is a bug that has been only in Mexico and South America. It has spread into southern 1/2 Texas, New Mexico, Arizona to California and I do now know how far toward Florida.

    THE KISSING BUG IS A BUG THAT LIVES IN MUD AND STRAW OF HOMES BUILT ( MUD & EARTH IS THE PROBLEM, NOT STUCCO OR PLASTER) . THE KISSING BUG LOVES CARBON DIOXIDE. IT COMES OUT AT NIGHT AND GOES TO AROUND THE MOUTH OF CHLIDREN AND ADULTS. IT BITES AND SUCKS BLOOD. ( The person never feels the bite or the crawling ) THEN SADLY JUST AFTER THAT IT’S INTESTINES MOVE AND IT HAS A BOWEL MOVEMENT. IN THE INTESTINES OF THE BUG IS A BACTERIA THAT MEANS DEATH TO HUMANS. IT GETS IN BLOOD STREAM FROM THE BITE SITE. IT SLOWLY OVER YEARS DESTROYS THE HEART/ INTESTINES OF THE PERSON AND CAN DESTROY OTHER AREAS. THEY CAN SLOWLY SHOW SIGNS OF ILLNESS AFTER SEVERAL YEARS OR DROP DEAD SUDDENLY. ( The parasite in the blood can be killed by antibiotics and the person does not have to die. The problem is knowledge you have it. After to many years it is to late and even with antibiotics to kill off the parasite the person will die, but they can live longer if treated to kill parasite in blood stream. THE KEY IS PREVENTION.. WALL CONSTRUCTION NOT USING MUD OR EARTH) ( PLEASE Google: 36 y/o man drops dead riding lawn mower on California golf course. No symptoms of illness )
    WHY I TELL YOU THIS IS BECAUSE THE STRAW HOMES MUST NOT USE MUD OR EARTH OF ANY KIND. ONLY STUCCO ETC. THE BUGS LIVE IN MUD PART OF STRAW MUD HOME.) NOTE MANY MIGRANT WORKERS COME FROM MEXICO ETC, AND DO NOT KNOW THEY CARRY IT. THE BUGS ARE SPREADING. THEY DO NOT JUST STAY IN HOT/ WARM ENVIRONMENTS.

    ( THINK ABOUT THIS! IF SEEDS CAN SPROUT THROUGH DRIED EARTH COVERED WITH PAINT, THE KISSING BUG CAN CRAWL THROUGH ALSO. IF ONLY STUCCO ETC IS USED, NO ENVIRONMENT FOR THEM TO LIVE AND MOVE IN.)

    I FIRST HEARD ABOUT THE KISSING BUG DISEASE THROUGH WORLD VISION ,THAT WAS GOING INTO CENTRAL AMERICA AND HELPING TO REPLACE MUD STRAW HOMES WITH MATERIAL THAT WOULD NOT ALLOW GROWTH OF THE KISSING BUGS.

    THANK YOU FOR YOUR HELP.
    PLEASE LOOK UP EVERYTHING ABOUT IT. ALSO CONTACT YOUR STATE CENTER FOR INFECTIOUS DISEASES CONTROL AND ASK QUESTIONS FOR FREE. ( THE MAIN CENTER INFECTIOUS DISEASES Is IN ALABAMA, I BELIEVE. THEY DEAL WITH THE WHOLE USA ) PLEASE ASK EVERYTHING THAT COULD BE DONE TO PREVENT PROBLEM WITH STRAW HOMES.

    I THINK STRAW HOMES THEY ARE A WONDERFUL IDEA. IT WOULD ALSO BE A WONDERFUL THING TO BUILD YOURSELF A STRAW HOME CABIN FOR RETREAT AREA OR CAMPING.

    1. Thanks for the warning and insight. From the research I have done, it seems that these bugs are most common in unkempt homes. Yes, they like the idea of mud plaster, but my sense is that they are more common in houses that are messy, or in fact DIRTY (walls included). It sounds like it is typical in Central and South America where living standards are lower. Not to say all of Central and South America has lower standards. What I mean is: in the areas where the standard is lower, there is more infestation. I think the best thing is to keep the house clean and be watchful for these little bugs. In many cases, they will not be an issue, but it only takes one carrying the disease to infect you. Be careful, but don’t panic. :p

  15. Clarification: Straw is a food source for farm animals… just not in the same way, or extent that hay is.
    Think of it as a supplementary source, sort of like pasta, in a meal–it is there primarily as filler, whereas the fruits and vegetables are the primary nutrient source in a good meal. You won’t live well or long on pasta only, but you will live long and well on a fruit and vegetable diet. That’s straw vs. hay.

    That said, when harvesting a grain crop, most farmers “chop” the straw and spread it over their fields (that’s what is coming out the back end of a combine). While it would be generous to say they do this to add value back into their land–indeed, land that is constantly baled does lose tilth and nutrient balance over time and is more subject to erosion–the real reason is that it is easier to seed into that field the next crop year if there isn’t a bunch of “trash” standing on it. Hay is ALWAYS baled for feed. Straw is baled mostly for bedding, but is also fed to livestock; but it is primarily just a way of dealing with an annoyance!

    Insulation value:
    When I break a piece of straw in two, I find a hollow tube. Cutting a piece of hay in two I find a more solid structure. Since dead air is the actual insulator, it stands to reason that for a given quantity, straw will be a better insulator than hay–if you don’t crush the life out of it.

  16. I have a straw bale house and noticed that there are some little bugs that almost look like fleas but are not. Are they attracted to the walls somehow and how do I get rid of them? Any help or suggestions please.

    1. Check out the post about psochids here at SB.com. That’s what they most likely are and they are telling you that there is moisture in your wall. Could be from plastering if the house is new or a leak. BEST of luck discovering the cause. Once the walls dry out, they will be gone.

  17. GREAT!
    BEYOND GREAT!
    QUESTION
    1. ARE YOU EVER INVITED TO A LOCATION, TO STAY ON SUPERVISOR
    OR GENERAL CONTRACTOR? IF SO, BESIDES THE HOTEL & MEALS
    WHAT IS YOUR CHARGE PER DAY? IF NOT, ‘ BOO-HOO’ WHICH BRINGS
    ON . . .

    QUESTION
    2. CAN YOU ADVISE OF SOMEONE WHO HAS MULTIPLE STRAW HOMES
    BUILT UNDER THEIR SUPERVISION?

    I remain in absolute AWE for certain

    Thanks so much

    The Pastor

    1. I do a lot of consulting for people and the cost varies from an hourly rate to an overall project rate. I don’t stay on site for more than a week at a time as I have family and other business commitments to attend to. My hourly rate is $50/hour and my weekly rate is $3000/week (if I stay on site) plus travel expenses. I usually use the week long time to train a small crew to continue the work while I am gone. I also offer year long consulting and other packages ranging from $5000 and up depending on what’s involved.

      I can do a lot from a consultant’s point of view and usually for a relatively inexpensive cost if you can provide the builders/labor force. I can train them, they can do the work. It’s the best of both worlds.

  18. Do Not build with Hay. Because of the moisture content and energy inside of a hay bale, heat is given off. Barn fires used to be a common occurrence in improperly ventilated hay barns. Encasing Hay with any kind of moisture or food energy into a wall could be potentially dangerous. I used to build hay fort structures in our barns for fun. We fed the hay out of course. The point is: Hay has too much energy and is for food. Straw is dry, essentially inedible, and can even be mixed with cement to strengthen it.. I have seen this done and am very happy with the results.

    1. Correct Richard except don’t use cement as plaster. It causes way too many problems with moisture issues and rot. Stick to lime or earthen plasters. Natural hydraulic lime is my favorite.

  19. I’m so happy to have found your webpage!
    I am wanting to lasagna compost my front lawn (drought in Ca!) for the summer. I am a city girl and cannot tell if the bales in my back yard, used to stop my daughter’s arrows, are hay or straw. They are three years old and have decayed but was hoping to use them (4 bales) for the composting project…is there a way to tell the difference?

    1. Chances are they are straw because straw is less expensive and typically used for things like archery targets. That said, you can look for obvious seed heads and investigate whether those heads (if present) have seeds in them or are stripped away. If they are stripped away or absent, then you have straw. If they are full of seeds, you have hay.

  20. I just got three bails of hay for our three backyard chickens from a local halloween pumpkin patch and read on this site about the dangers of building with mud and straw- ” kissing bugs”! are we in any danger if the bales ( straw, I think) are under our back porch with by the coop? the bales are still tied to the top of my car and I’m considering taking them back!

  21. Let me dispose of a myth you have. Decomposition CANNOT lead to spontaneous combustion. The reason is simple. All microbes (at least those that don’t live near sulfur vents in the ocean) die at 160 degree F. Remember the book F 451? That is the minimum temp necessary for paper and all other straw like things to combust. Most likely that myth came because some kids were smoking behind the barn and the dried bails caught fire. Rather than get a wooping, they told their parents them there fancy words “spontaneous combustion” they learned in school. There is also a secondary reason, and that is moisture is necessary for decomposition and there is enough of that so you can’t even easily light a steaming compost pile.

  22. Hello. What a lot to learn about the difference between hay and straw…who knew?!

    I’m interested in straw bale gardening; I received a book on the subject, and that’s where I began my tutorial on the difference between straw and hay. Now my question is “where do I find straw”? It seems that there are many websites that list hay as their commodity when it was straw I was asking for.

    How do I know if I’m getting true straw? Do you have any suggestions? I would think that living near Fort Worth, Texas would provide plenty of sources.

    Thank you for any information / assistance you can provide.

  23. Dear Andrew,

    I am hoping to build a house with straw bale as insulation here in Australia. I would like to clad the house with corrugated iron (it’s called Colorbond here in Oz and has a color baked on) on the outside and drywall (gyprock here) on the inside.

    I note that most of the discussion of straw bale houses discusses rendering. Do straw bale houses need to be rendered? Would the straw bales need some form of barrier between the bales and the corrugated iron? Or would a careful construction of the corrugated iron wall sufficiently protect the bales?

    Thanks for your help,

    John

    1. Hi John. I think you will find that if you plan for a color bond exterior with drywall interior that you will be better off not building with bales. The construction process for SB is very labor intensive and if all of the value of that labor will be hidden behind drywall and siding, you may as well use standard insulation materials that are easier to install. I say this because you will need to add elements to the bale house that would otherwise not be necessary so that you can attach the siding and the drywall. That is extra framing, and/or framing that is placed in such a manner as to provide the backing where the bales are set to fit the span in between those members (which allows for thermal bridging).

      So the short answer is yes, it can be done. The longer answer is that it is more labor and material intensive.

  24. Regarding spontaneous combustion, the commenter may be right that a bale cannot burst into flame but I can tell you from years of experience feeding horses that you can open a bale of hay and find heat and mold and nastiness in the center. I was told it was from the hay being baled too wet, and it was especially common in alfalfa bales – higher protein content than grass hay, and finer stalk. I’ve also seen straw bales that were very dirty and moldy inside. If I was building a house of straw bales, I’d want to see the field before baling to check out how ‘clean’ the field is, i.e. how many weeds, how dry, etc.). Here in western Oregon, bales of straw and hay can be hit with rain during the baling/drying process and you also need to check and see where it is stored after baling. Most are left outside and can gain a lot of moisture from the ground and from rain, especially the outer bales.

  25. I’ve read that if you feed sprouted fodder to your animals you still need to feed them hay for roughage but that it can be “bad” hay. I take that to mean hay that has been stored a long time and is dry or the final cutting of the year or hay with weeds in it.

    Do you think straw could be used instead since they are getting the nutrition from the fodder?

    1. Hi Steve. I have no idea, sorry. I use straw to build houses with and I do not know what is best for animals. That said, I have seen locals farmers giving straw to their cattle, but I don’t know if that is a good idea or not.

  26. I was going to use leftover hay for mulch from a hayride to put under my durantas so it could retain the water more. in way South Texas its around a 100 all summer.Should I foresee any problems, like root rot. Thanks

  27. Hi. Im planning to build a staw house for me and my wife here in Mexico, there is little information about using sorghum straw bales wich is very abundant in location would you recomend usin sorghum for construction? Thank you!!

    1. Hola Juan. Creo que sorghum es bien. Nunca lo he utilizado, pero parece que funcionaría. Hope it is okay to practice my Spanish. I’m learning. 🙂 In case I didn’t say it well…

      I think Sorghum is good. I have never used it but is seems like it would work. The thicker the stalks, the harder it will be to use because of resizing bales. Good luck.

  28. I have an elephant made with straw and roped together. I would like to put this in my yard but, I cannot find anything that will tell me how to protect this from the elements.
    Will this withstand the elements in Florida with no preparation?

    1. I would not put it in the weather without a roof to protect it, personally. Straw is weather resistant to some extent, but prolonged exposure to sun, oxygen and water will cause it to rot, as is true of any organic material.

  29. Hi Andrew,
    I’m wondering if you know whether straw bale can cause an allergic reaction if used in a cabin. My son is highly allergic to wheat,oats and barley and also has asthma induced by environmental allergies. He is going to a camp field trip and I just read that the cabins are built from straw bale. Does straw bale still contain the good proteins from the grains used?
    Thanks,

    1. Hi Martha. It is different for everyone as each person’s allergy is different than the next. That said, I have not heard of people having issues with SB homes in terms of allergies. The bales are sealed behind a thick layer of plaster, and as such, do not have direct contact with the habitable space. I would not suggest your son be on site until the plaster is complete as the loose straw is irritating to almost anyone who breathes it.

  30. Hi Martha,

    I am considering using straw bales for walls for a shed I am building. The walls are 4m high and in total including the 3 sides 44m long. One side is left open. The roof and structure is sound, and so all I need is a way to block up the sides.

    I like the idea of straw. May I please pick your brain and ask a few questions.

    1. With what do you plaster the straw?
    2. Any ideas on an affordable method to secure the bales from falling?

    If I can get this to work it will be a very very exciting day. Imagine the possibilities.

    I hope you can help.

    Kind regards
    Matthew van Lingen.

    1. Hi Matthew. I think this message is intended for me and not Martha so I’m going to jump in. I plaster my walls with Natural Hydraulic Lime Plaster. In regards to your second question, there are a lot of construction details that need to be considered, so it’s not as simple as me saying “do this” and you’ll be fine. I am a firm believer in using 2″ x 2″ welded wire mesh to keep my walls tight and secure. Again, there is a lot to that answer that isn’t covered here. You can find the details on the site, in our DVDs, and at our hands-on classes. Good luck with your project.

  31. Andrew I am thinking of using straw bales to put as a wall for my fifth wheel to keep the wind out since I live in my fifth wheel. But I live in an RV park and cannot make Miss do the E straw bales can they come wrapped and will it mold during the winter

    1. Hi Ana. I hear you. You can do one of two things:
      1. Place the bales temporarily in position and replace them each year. They will start to rot a little, but not so much that it causes problems.
      2. Create a permanent installation where the bales are placed on a raised “foundation” (could be pressure treated wood framing) and then plastered. This will provide adequate protection for many years. You could even wrap them in tyvek and then wire mesh to provide extra water resistance.

  32. hello I just want to know the different uses of hay bales could you please assist me to find out the different uses of hay bales

  33. Just one point, we do feed straw in Norther Ireland ,it is mixed with silage and or grain to make a mixed forage to feed cattle with in Winter.

  34. Hi Andrew,

    I am considering using straw bales, enclosed in leather or canvas covers as modular sofa sectionals indoors. Is there a risk of mold or pests if the bales have been properly dried and inspected.

    Thanks and great content!

  35. Good day Andrew.
    I’ll get straight to the point. Can I use sudan bales for building my shed walls. Long story but i can’t find any more straw bales and I need to get enough to finish. Will sudan bales work ok?
    Anthony

    1. Hi Anthony. I would not recommend that as Sudan Bales are a live crop, grass. That means that they have food value and as such could invite problems with rodents and other critters. If you are only in need of a few bales to finish your project, I would recommend going to a farm supply store and buying bales through them. They will be expensive, but the result will be less expensive than adding a food source bale to your home. Good luck.

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