I published my preferred earthbag foundation method in my new book Earthbag Building Guide. It still seems to be the strongest method because it locks 1-1/2 courses of earthbags below grade. With this method, the site is raised prior to building the foundation with stable fill material such as road base, and compacted by driving a vehicle back and forth on top in different directions. It’s the best method I know, especially for large projects.
But it’s always good to consider alternative methods. In the drawings above you can see a second way to build earthbag foundations. The main difference is the foundation starts at existing grade and the fill material is added later. The process is divided into two main steps.
Step 1: Make a rubble trench foundation at existing grade. Dig a trench slightly wider than your earthbags, add a French drain if necessary and fill with gravel and/or rubble.
Step 2: Place at least two courses of gravel bags (double-bagged for strength) with barbed wire between courses. Add sand/gravel fill material on the inside to prevent wicking of moisture, and tamp until stable. Add and compact stable fill material on the outside so water flows away from the building. Pour a concrete threshold or build a stone threshold at finished floor height for each door. This creates a strong, level base to support the door bucks. Let the concrete dry a few days and then you can set the door bucks and continue placing earthbags.
9 thoughts on “Another Earthbag Foundation Method”
I live in Nigeria . Please what best of earthbag foundation can I use as underground water sips through the side walls and floor to flood my pen as the rains are here again. It’s a mud type soil
I’m seriously considering an earthbag home, but have a lot of hurdles to overcome since I have a half acre in a neighborhood. Due to code/permitting issues in my part of Texas I know I would be forced to use a regular concrete foundation…if they’ll agree to sign off on the earthbag construction at all. (Frost heave is not an issue.)
I’d like to be prepared if I can go forward, but I haven’t found any resources online for using a full slab since most folks are building off grid, or at least out in unincorporated locations, and can use the gravel trench method for a simple footer.
Can you point me in the right direction (links or books) for anyone who has successfully built an earthbag home on a slab? Thanks for any info.
An engineer can design a monolithic slab foundation with thickened edges to support the earthbags. There’s no specific book or resource that I know of.
Thanks so much. I’ll look into that.
Dear Owen, after buy and spending time studying your great book I’m finally starting building my first earthbag house in Indonesia.
Considering I’m building on a slope land, and in Indonesia there’s 4 months rainy season and earthquake risk, with my building contractor we decide to make à rubble tranch foundation and on the top a level concrete slab with horizontal steels inside.
My questions are:
1) how do I link the first earthbag course with the concrete slab? Without any connection the whole earthbag house will just lay on concrete slab by his weight. Is it enough?
2) is it necessary to place 2 courses of earthbags down treashold level or can I use the concrete slab as treashold?
I’d really appreciate your suggestions and help.
Thanks for your great job
Anchor the earthbags above the slab with embedded eye bolts etc. for connecting tie downs. 1/4″ poly rope tie downs are good about every 30″. You can do the threshold lots of ways.
Thanks a lot Owen for your quick reply
Yes I live in Kentucky where the winter months can be very cold wet and freezing down to 36″-38″ what is the best foundation for this climate and should I still keep the foundation at 36″s??
If there are no codes then I’d use a normal gravel bag foundation with rigid foam insulation on the outside.