Engineer-approved TJI/Earthbag System

Vertical TJIs on piers, combined with insulated earthbags, create a fast, superinsulated wall system. (click to enlarge)
Vertical TJIs on piers, combined with insulated earthbags, create a fast, superinsulated wall system. (click to enlarge)

I’ve been reading about the building boom going on in Wyoming and the Dakotas from all the oil and gas exploration. There’s currently a severe shortage of affordable housing in the area. But the climate is very harsh and so conventional earthbag building is not so practical. We’re always searching for faster, easier, lower cost, better ways of building. This opportunity got me thinking about how to optimize code-approved earthbag building in extremely cold climates with short building seasons.

Precision Structural Engineering, Inc. is willing to approve an innovative building system that uses vertical TJIs (engineered joists) on piers and scoria-filled earthbags on rubble trench between piers. This is similar to the EcoBeam system, where earthbags are used as fill between posts. Differences include: scoria-filled bags create an insulated foundation; tubes are recommended instead of bags to speed construction; earthbag upper walls (area above where moisture can cause problems) could be filled with perlite, vermiculite or other material for higher R-value. Plans must be adapted for each area to meet wind and seismic loads.

– This building method would include the first code-approved insulated earthbag foundation.
– Piers cost less and use less concrete than typical foundations.
– Walls could be thinner than typical earthbag walls to conserve space. (12” is suggested. Perlite = R-3 x 12” = R-36, which is double or triple most wood framed walls.)
– Siding could be added to speed construction.
– Insulated TJI or wood box bond beam speeds construction.

Contact Precision Structural Engineering, Inc. for details

[Between Bill Taha and sub-consultants, they carry licenses in 48 states nationwide. They have also completed projects in 14 countries internationally and counting. PSE, Inc. developed the first engineer-approved earthbag system that can be widely adapted to most any design. See]

9 thoughts on “Engineer-approved TJI/Earthbag System”

  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:


Leave a Comment

This site uses Akismet to reduce spam. Learn how your comment data is processed.