Anchor Bolts for Toe Ups in Straw Bale Construction

Written by Andrew Morrison

anchor bolt assortmentThere are so many options for anchor bolts for toe ups these days that it is hard to know what to use. I believe I have found the best option for most straw bale projects. Keep in mind that with both interior and exterior toe ups, there are a LOT of anchor bolts in a bale house. Because of this, expense has to be considered; however, it should not be the main factor.

j bolt
The standard J-Bolt, shown above, is used in most sill/toe up to concrete foundation application. The problem with the j bolt is that it has to be set in place before the concrete is poured. This means that the finishing of the concrete is harder to accomplish in a flat, even surface. Having to trowel around each of the many bolts is a pain, especially those located for the interior toe ups. Secondly, the interior toe ups are not usually installed until later in the building process and so the anchor bolts, sticking out of the foundation, become a major tripping hazard.
pin style anchor bolt
I have moved toward using the above pin style anchors by Simpson Strong Ties® instead of the J-Bolts where permitted by code and or design (be sure to check with your engineer or code official). These bolts are easy to install after the concrete has set up and right before you actually need them. Much safer all the way around in terms of tripping, etc.. Be sure you don’t have any radiant floor heating tubes in the area as hitting one of those when installing a bolt will ruin your day.

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19 Responses

  1. There is another alternative that you might consider which provides a very, very solid anchor, though its application can be some what obnoxious. You can use sulfur to set anchors.

    Sulfur can be purchased inexpensively from agricultural stores which provide bulk animal medications. Powdered sulfur is occasionally used for sheep medication and is less expensive than the more pure powdered sulfur obtained from chemical companies or science stores.

    Use a hammer drill that will provide a hole slightly larger than the size of the head of the bolt you are using. Carriage bolts work best. Insert the bolt, head down and then use a lead ladle or some similar device and a propane or acetylene torch to melt a quantity of sulfur sufficient to fill the remaining space in the hole. Use a particulate respirator when doing this job for melting sulfur is the brimstone of “fire and brimstone” notoriety and has the awful smell of rotten ages. It also can start on fire if you are not careful and produces an invisible flame, like alcohol; So be very, very careful in the process. Though the sulfur starts out yellow, it turns to purple when melted and remains that color after cooling. Once cooled around the inserted bolt it is nearly impossible to remove. I know this sounds like a significant hassle, but if you have allot of bolts to do it can be less expensive than the fix described above.

  2. Folks: That should be “awful smell of rotten eggs” and not “ages”. I was not making a negative remark about those among us who are chronologically more challenged than others…after all I am one of those folks! Just one of those absent minded professor things I guess.

  3. Thanks Andrew and thanks Dr. Miller; I have beeing gathering info. for some time now on Straw Bale Building and can’t wait to start my own project. Andrew’s site is by far the best I have ever consulted. I will be asking some questions for sure in the future.
    Until then,
    Jorge Benet

  4. Bales can be placed on edge, but I don’t recommend doing it. There is a blog post on the site that discusses this further if you are interested in my reasoning. The toe ups do not have any twine involved in their construction. They are wood frame and bolted to the foundation. The bales are not attached to them with twine at all. I use 20d nails to grab the bottom of the bales.

  5. Here in Chile when pouring the foundation, the builders use pieces of rebar aprox. 70 centimeters long, doubled in a U shape on the portion that is pushed into the foundation. It is then doubled over a 2×4 which is used as the bottom plate. They finish it off with some recycled nails from the disassembled foundation forms, doubling the nails over the rebar. It makes for a strong and easy connection to the foundation, and is very inexpensive as it requires little prefab materiales.

  6. Regarding the ‘toe up’; I have seen designs with pea gravel and also with rigid foam insulation to separate the bales from the concrete. Two very different materials; if you are looking to insure moisture escape as well as isolation for the bales, how does the rigid foam work? And what about degradation?

  7. Regarding “toe-up” foam vs. gravel, which is better and why?

    can you notify me by email of follow up comments; I missed that option.

  8. I agree with you. I only ever use rigid foam for half of the toe up, the exterior half, to allow for drainage. Without exposure to light, the foam will last a long time.

  9. I prefer gravel for its ability to drain. A half section of foam is a good idea for added insulation (the exterior half of the toe up). Foam is good on a second floor where massive water leaks will not likely stay on the floor anyway and build up. The foam is lighter and helps with the engineering requirements of the floor system.

  10. Regarding laying bales on edge verses flat. In my own home construction there was a necessity in doing this, at least on a portion of the exterior wall. A portion of my home is recycled, that is it was an existing two story structure which i disassembled from the roof down to the platform of the second story. The first story was concrete block. In creating an insulating envelope from bales I began with a rubble foundation at the base of the concrete block wall and then laid bales vertically until i got to the second story. With the second story I took salvaged 2 x 4s glued and screwed together to make 4 x 4s and constructed a post and beam structure to support the new roof. Bales covering the second story were laid flat (horizontal) so that they could be notched around the 4 x 4 posts. By doing this I created a flat interior wall and a flat exterior wall which aligned vertically with the edge laid bales of the first story. Understand of course, that “flat” is a relative term in straw bale construction.

  11. Hi Andrew. I am like Jorge Benet. Never stop gathering info, The more you learn the better you do. Knowledge is power. Thanks Dr miller, I will use your advise. Andrew is there a spesific reason why you use wood for the toe ups or can I use brick instead. I understand the wood been for the nails. I will use a plastic sheet dampstop before putting the gravel in order to prevent damp getting threw the bricks. Although you dont strap the bales to the concrete floor, dont you think it gives more stability and strengh to the bales by pulling them down. I listen. Greetings

  12. Hi Barnie,
    The biggest problem I see with using brick is that it makes it hard to anchor the bales as you suggest. I use nails out of the top of the toe ups to grab the bales and the I use the toe ups to attach the framing and mesh in a post and beam structure or to attach the strapping in a load bearing structure. The toe ups are attached to the foundation via the anchor bolts and that ties the entire system to the foundation through transfer of load. In other words, the toe ups are attached to the foundation, the bales and/or frame are attached to the toe ups, the roof is attached to the frame or toe ups (via strapping), and so the whole assembly is attached to the foundation. This is important for uplift and general structural stability. Hope that makes sense. I think the brick would not attach to the foundation well in terms of uplift. Even if mortared in place, they would be at risk of uplift forces since mortar is not very strong in tensile strength. It works mainly in compression.

  13. Hi Andrew. Thanks it make sense. In other words the bricks it self is not the problem, it is to get the entire system anchored to the foundation and in order to do that the toe ups (using 4×4 wood) will be the easiest way. My project is floor hight and I will start shortly with the bales provided I get a solution with the NHL.

  14. I am looking for information on actual sales of straw bale homes to help with the appraisal phase of my construction loan for a SB home. I am building in NH but the appraiser will take info from anywhere. Most website list FOR SALE but I need some actual sales for comps. I am so close to getting started but I just have to wrap of the sticky little detail of financing! Thanks for any help.

  15. Looking into strawbale homes the thing that has fascinated me is that ability to shape the walls (curved specifically) So I’m currently working on a design that has curved walls. I would like to use IFC for the same reason ( design flexibility) I found a company that makes radius forms but they are only 6″ thick wanted to know if that is enough? My question is how thick are the foundation walls typically?

  16. Foundation walls can be standard thickness as long as the floor supporting the bales can handle the extra weight. For slabs, this is no problem, but for framed floors or earthen floors, you have to confirm the loads can be carried.

  17. Hi Rebecca. This is tough because an earthbag foundation doesn’t offer any tensile strength or resistance to uplift. As such, attaching toe ups won’t ever be as strong as on a concrete foundation. You can use strapping that wraps under the foundation and up/over the toe ups. Again, it won’t be a high quality attachment, but it’s the best you can do. Good luck.

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