Debunking the Rodent Myth

Written by Andrew Morrison

I know, I know…For most of you this is old information, BUT if there are any folks out there that still have a worry in their minds (and it’s OK if you do!) about straw bale houses and rodent invasions, this latest “Straw Bale Minute” is a must watch. Trust me, rodents would much prefer to set up residence in your neighbor’s conventionally built house with lovely pink insulation than live in straw bale walls. You can hear why in this “Minute” below:

 

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19 Responses

  1. Our strawbale house only had mice issues in the conventional constructed areas where they came down through the roof into the utility area and also into chase areas under tall windows where they construction a boxed in area. Any place of regular straw bale construction & practices had no mice issues at all. This was a big lesson learned & what can drive you crazy trying to secure conventional built sub-areas. We learned what we will do differently on the next build.

  2. Liked the mice rodent info. Here is my question. We have land in Cibolla National Forest near Magdalena, New Mexico and it is populated with several different rates/mice. You have answered part of my question but the other is the storage of bales at the site, and while they are stored they acquire livein rodents. Also say we are working on site and our bales are sitting around open on one side to the elements (not coated yet) and the desperate critters get in then? Would you say at this point the answer is the fact that the bales are so dense it would be nearly impossible for them to enter?

  3. In a loose stack of bales, you will get some rodents, i.e. when your bales are waiting on site to be used. They will make little nests in the space between the bales and may even scratch and chew out a little depression in the top of a bale as a nest. They won’t, however, cause serious damage to the bales. Be sure to stack the bottom bales on edge so that the twine is not on the bottom of the stack. Rodents have a knack for chewing those strings (where they meet the pallets) and ruining those bales. If the bales are on edge, that problem will be eliminated. This is old school farmer info! Some folks will recommend that you throw lime powder on the bale stack as you build it (when storing the bales) as a means to deter the rodents. I have seen this done and have seen mice still making nests in the stack. The only difference is that now you have bales that blow lime powder all over the place whenever you touch them or move them. Not a good situation and not worth the (poor) results you will get from the action.

    Once the bales are in the walls, the density comes into play. Even if they were to get in, they would come out as soon as the plaster starts to be applies because they would see that they would be trapped. This happened in Australia on a build I did. The area had a MASSIVE mouse infestation (the whole shire due to the killing off of the foxes). The walls would fill with mice each night after we built. On the final night of the workshop, a guy sleeping inside the freshly plastered walls kept hearing a weird sound. He discovered that the mice were scratching their way OUT of the walls and running to freedom. After three days of this (yes, three days of mouse exodus…maybe five mice/day) it stopped. The owner has never had a problem since then. Keep in mind, this is in a shire with a major mouse infestation. The ground would literally shift like a blanket of mice when a flashlight was shone on it.

  4. Hi Andrew just wondering how to secure the straw bales when putting them on top of one and other while building the wall ? Also do they have to B compressed and held down in some manner while building the wall up. ?
    Don’t know if this is two questions or one in the same ?
    Thank U Churchie
    Also I enjoy receiving your e mails and the subjects talked about 🙂

  5. The bales should be stacked tightly against and around the frame. This will hold them in place during installation. If you plan to take more than 2-3 days to bale an area, then you will want to add squash blocks (horizontal pieces of 2×4 between posts) on top of bale courses to tighten them up. This is not necessary in most cases. It is usually required where the stack of bales is not in running bond, i.e. it is a stack of 7 bales piled on top of each other with nothing on either side.

    Once the bales are up, they will be held tightly in place by the frame itself. I recommend that people build their top bale stop (the flat framing that the bales are pressed tightly against at the top of the wall) to be 2-3″ lower than the bales are tall. Put another way:

    Height of the bales X number of courses + height of toe ups – 2 to 3 inches for compression. The answer to this equation is where you place the bottom of your bale stop to compress the wall during the construction.

    Thanks for your kind words!

  6. Aloha Andrew,

    My partner and I are building a load-bearing structure here in New Brunswick, Canada.

    We weren’t able to get any plaster on the walls this season so we’ve just wrapped the house in tyvek to close everything up as best as we could. Well, I’ve had to undo a bit of that house-wrap after having discovered a non-load-bearing wall of ours got pummelled by 80kmph winds and actually bowed most the wall inward. Inside I discovered some broken twine halfway up a balewall in a corner of our house. It’s troubling to me because that corner of ours has already been weakened by a previous mishap (foolishly failed to use corner guides + strong wind actually MOVED the entire roof over a few inches). What the hell should I do? Do the vermin matter much? Feel free to chime in on our other problems….

    Thanks for reading. And thanks muchly for your work. People have shared heaps of information with us during this, our stressful build.

    Aeron

  7. Hi Aeron. Sorry for your challenges. That makes a stressful job (building) even more stressful. The roof issue can be handled by installing some type of connection point between the roof and the foundation. That can be strapping material, threaded rod, or cables. The key is that it needs to have a direct connection to the foundation and cannot simply sit atop the bales, even if anchored to the bales. I prefer to use Cordstrap and then once fully compressed, welded wire mesh on both sides of the wall. Be sure that the roof is in a plumb line from the foundation before you make your connections.

    For the wall bowing in, the welded wire mesh will help a LOT with that, especially once tied through with baling twine on 18″ centers both directions. Also, the compression of the wall with the threaded rod, cables, or strapping will tighten everything up. If you need to leave it for an even longer period of time without those supports, you may need to provide temporary bracing in the form of framing lumber and plywood. Hopefully you’ve been able to get past this stage of waiting and have secured the walls accordingly.

  8. As I’m building the rodents are cutting the baling twine. Do I need to take the wall down and start again or is it ok to leave the bales that are tight without twine and hope the plaster keeps them together?

  9. Hi Ronan. That seems like a pretty significant rodent issue. The most important thing will be to make sure that they don’t get in once the house is plastered. You should not be losing baling twine in the wall to rodents. It’s possible that the walls will be fine with the lost twine as the mesh and plaster will hold things together; however, that’s impossible for me to say with full confidence without seeing your project and the tightness of the bales. There are those who cut all the strings on the bales once the walls are built (I don’t agree with that approach, but some people still do it) and their walls don’t fall down. You will end up with a wall made up of loose straw straw though, so that makes repairs and remodeling harder, especially if you have water damage that requires the removal of a bale.

  10. Is a cement foundation the only option for straw bale builds in rural areas to avoid rodents entering from underneath?

  11. There are other options available; however, concrete is the best option when it comes to structural support for the house. Further, if code approval is required then you will likely have to use concrete in some form.

  12. That is a straight up lie. Rats and mice love straw and other insects love to live in straw. Anyone with half a brain can figure that out go get a rat put some straw down there and find out what a nice house he likes to make with it.

  13. Hi Lisa. You are clearly energized by this post; however, I don’t appreciate you calling me a liar. I think there is a different way to have this conversation and I’ll do my part with my response. To be clear, I don’t disagree with you that rodents do indeed like straw, but that is not the point of this discussion. A loose pile of straw is very different from a tightly packed wall, wrapped in welded wire mesh and other stucco backing, and coated in 1-1/2″ of lime plaster. A well constructed straw bale wall has been shown to be impenetrable to rodents, and even if they could get in, there would be nowhere for them to go because the bales are packed so tightly together. There are literally thousands of straw bale houses around the world that stand as testimony to this statement and blog post. There are lots of loose piles of straw that house rodents. There is a difference.

  14. Our straw bale cabin is infested with mice right now. I am not sure exactly how they are getting in but once into the bales, they have chewed through the inner mud surface in four places. Obviously tunnels in the tightly packed bales. If I close up one hole jamming in steel wool, then remudding, new holes appear just beside. I tried every trick I know and it is very frustrating.
    I’m here to say that Yes, mice do like to live in straw bale walls and they are adept at tunneling through bales.

  15. I am trying to decide between earthbag building and strawbale in our very humid and hot (south Georgia) climate. It seems like mice cause problems if your plaster is off or your caulking job is insecure? I would appreciate any info/opinions on the two, and which one would suit my situation. Also: not related to strawbale, but can you actually buid a two story earthbag house?? And would it overheat in the summer? Thanks!!

  16. Forgive me if this has already been addressed elsewhere. I use hardware cloth to protect chestnut seeds from various vermits (and they are all wiley!) while they are stratifying over winter. It is the same stuff that stucco is adhered to on houses. Perhaps a layer of this stuff would prevent unwanted house guests? I’m not sure if it would be required on both the outside and inside. I would think that would be the best defense. Would love to hear if anyone else has already tried this. I am on the brink of building a small straw bale structure myself and am interested in other’s experiences.

  17. Hi Nell, There are a lot of variables when deciding which construction method will best suit your needs. You’ll have to prioritize your needs and educate yourself about the pros and cons of the building systems you are interested in using. I can’t tell if straw bale will suit your needs better than earthbag construction or vise visa. I can tell you there is a lot of helpful information on our website to inform you about straw bale construction. This article HERE is about a straw bale home built in Thailand in a hot and humid climate like southern Georgia. Read the article and the following comments to learn from others’ experiences in this type of climate. Perhaps there is a nugget in there that helps you in your decision process.

  18. Hi Sandy, Diamond mesh and 1/2″x 1/2″ hardware cloth are often used to support plaster/stucco and help prevent cracking. Their application is often used to bridge dissimilar materials and cover expanses of material that can not support plaster on their own (i.e., wood, foam, or metal). This type of mesh can theoretically be used to cover an entire wall but tends to be less cost-effective. The small size of the mesh has the potential to help keep rodents out of the wall; however, if your bale wall is detailed and plastered as recommended, there should not be access into the wall.

    2″x2″ welded wire mesh is the typical material used to cover the entire wall and provide plaster support and lateral shear strength. Here are a few links to blog posts addressing what type of mesh to use.
    What Type of Mesh to Use in a Straw Bale Build
    Firmly Attach Mesh to Protect Your Plaster
    https://strawbale.com/plastering-without-mesh/

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