Engineer-approved TJI/Earthbag System — 9 Comments

  1. Wouldn’t adding siding regardless of whether it is hardboard, milled wood or t-111 raise the cost substantially? I know there would be some time savings over,plaster, but on a fair sized house would the cost justify the time savings?
    Not only do you have the cost of the siding itself, but the trim, nails and finish. If a vapor barrier is also needed there is the cost of it. Putting siding on supports at 3ft centers may not work (4ft sheets) or provide the structural integrity most siding requires (7/16 inch thickness).

    Another concern is how many DIYers have the skill and tools necessary to install siding correctly? Of course they could hire it out, but then again that adds to the cost.

    I like the idea of using bags as insulating infill, but I believe using scoria and plaster would be a much more affordable/doable DIY system. Using structural elements at specific span points to carry the roof load,and infilled with scoria earth bags would save money. You would save on concrete foundations, the labor and material for the tjis, the cost of siding and related materials. The doors and windows could be fastened into the earthbags as per your book. The DIY owner builder wouldn’t need to worry about a vapor barrier, or the skills necessary to install siding. In colder climates a second layer of bags filled with perlite could be added around the outside. Large roof overhangs would protect the lime stabilized plaster.

  2. I like this idea. Get the frame built and overhang on to protect the bags. What is the reasoning for the supports around the door and window? Couldn’t those be eliminated if the beam was sized to carry the roof load across the entire span?

    • TJIs next to doors and windows provide sturdy anchor points to attach window and door frames. Adding TJIs every 3′ or so makes it possible to use ‘flimsy’ tubes of perlite, etc. and add siding.

  3. This is definitely relevant to my interests. Looking forward to more developments in earthbag building suitable for South Dakota’s extremes. My hope is to one day build a chonburi (or something similar) there. Though I still like the idea of having plenty of thermal mass inside.

    • You’ll have plenty of thermal mass with thick plaster and mass floors (concrete, brick, etc.). They key is getting enough insulation.

      A major advantage of this design is being able to quickly get the walls and roof built and then do the earthbag insulation. You could even add siding, windows and doors and get it enclosed first. Do plumbing and electric before insulation. So the building process is greatly changed to your advantage, which is great if it’s below zero..

    • I’m really confused about this “scoria” which I learn is lava rock. How is it more energy efficient that it adds to superadobe earthbag building thermal mass? What exactly does it do? I was looking at building an earthbag or earth sheltered home, but I keep seeing scoria mentioned as a better choice for colder climates–Montana is mine.

      • My response just got accidentally deleted, so I’ll just recap it briefly. Scoria is used as insulation. It can be used in the bags or on the outside of walls. Search this site for the details using the built-in search engine. Scoria is probably available in Montana through landscape suppliers. You want to build a superinsulated home in cold climates like Montana and scoria would work perfectly. Start out by building something small like a tool shed or a casita:

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