Do earthbags really become hard as rock or is this exaggeration? I did a little experiment on the roundhouse we’re currently building to find out.

The answer depends primarily on the choice of fill material and the degree of compaction. The moisture content and curing process also play a role. We used road base – the material used under roads in many parts of the world – moistened slightly and tamped solid. The video shows the result after about one or two weeks of drying.

Note the ringing ‘ching-ching’ sound when I tap the earthbags with a putty knife. It almost sounds like I’m hitting stone. I tap a compressed earth block (CEB) for comparison. CEBs contain about 6% cement and are rammed in a press at high pressure, so you expect them to be harder. But in reality they’re fairly similar as you can hear for yourself. In both examples, densely compacting correct soil mixtures create very strong building materials. They begin to approach the strength of stone at a fraction of the cost and labor.


Comments

Earthbags Can Be Almost Hard as Rock — 4 Comments

  1. Thats’ what I figured, but the reason I ask is that I have 2 sons, 7 and 8 years old, who could fill sacks now and if I could store them for a later use, that would be great. Can you think of any way that I could go work around your concerns? I had in mind filling the bags, stacking on pallets and cover until needed.

    Thanks.

    Jonathan

    • No. You’d be wasting your time. You have to fill the bags with damp soil and tamp soon thereafter to achieve solid walls. Your method would produce weak bags of dirt that will not tamp solid.

  2. Is it feasible to fill and store bags to be used later? Will they be too hard to use at a later date, even if covered and protected from water?

    Thanks.

    Jonathan

    • There are two major problems with this:
      1. Wasted time and labor moving bags around (it’s easier to fill bags on the wall).
      2. You need a certain amount of moisture in the soil for maximum compaction. You’ll want to mix water with the soil before filling the bags.

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