Earth Block and Earthbag Testing

Full text of the video is available on my Naturalhouse’s YouTube channel. This blog post will focus on summarizing the test results. Please note that even though half the samples were earthen blocks, you can do these same tests on earthbags to help develop a good soil mix. A link to additional tests can be found at end of this blog post. Also note, although I say “clay” for brevity it’s actually clay soil not pure clay that’s used in all these tests.

Earth Block and Earthbag Testing Results (click to enlarge)

The strongest sample turned out to be the earthbag made with vetiver, clay soil and rice hulls. This sample not only passed every test, including zero damage in the drop test, it also had a distinctly different feel than the others. It made a ringing sound when it was dropped that reminded me of clay brick. The sample was lighter weight due to the hulls, and, of course, would have improved insulation value. It probably gained strength from compaction and the long vetiver fibers.

Adding rice hulls to adobe and other forms of earthen construction is an ancient process that begs further research. For instance, I just learned rice hull/clay was the traditional method for building houses in Taiwan, and now the high cost of energy for air conditioning in Taiwan is creating renewed interest in this ancient technique. (No air conditioning needed in a properly designed adobe or earthbag house.) Note the similarity with straw/clay that has proven a huge success in Europe for centuries.

For additional soil tests, please refer to Patti Stouter’s excellent soil testing guide Soil Tests for Earthbag.

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Cheap and Easy Brick Floors

Cheap and easy compressed earth block (CEB) floors

Here’s a great, low cost way to build floors with compressed earth blocks. This Instructable is by Velacreations. Visit their website for more great ideas.

When considering what material to use for a floor, few people look beyond a concrete slab, with something like tile or carpet as a finish. For us, however, there were several factors that made a stabilized compressed earth brick (SCEB) [or just CEB for short] floor far more appealing, including cost, skill, and time required.

Read the rest of the article for free at Cheap and Easy Brick Floors Instructable

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Vetiver and Rice Hull/Clay

If you’ve been watching our videos, you’ve seen us making various earthen blocks. This one here is the best one so far. It has clay and rice hulls. Another very good block was the clay with vetiver grass. So I had the idea to combine the best – the rice hulls and the vetiver. That’s what we’re testing today. This block back here is adobe, just the traditional adobe mix. We’re using this wood form that’s 10”x14”x6” high. That’s a typical size earthen block. You could put these same materials in earthbags, but it’s a lot of extra work. It would only be worthwhile probably if you wanted something special like a lightweight insulated earthbag.

We’re using the same basic ingredients – rice hulls, chopped vetiver for fiber to hold the block together, sifted sand and clay soil. This is not pure clay, this is clay soil. You have to experiment with your own soil and ingredients to get the right mix, but this is what we’ve been using approximately 2:1 — two parts clay soil to one part sand, one part rice hulls, one part vetiver, and enough water to make a stiff mix, but no extra water. Add the clay first – the clay soil actually – with a little bit of water and let it soak. This saves a lot of mixing. Add a little at a time. And again, it would be easier to make this in large quantities in a pit or on a large tarp. We’re just making one small sample here. Add the ingredients in layers to reduce mixing. Add the fiber at the end to make mixing easier.

I like the vetiver grass, because it adds termite resistance and tensile strength. We made a second small batch in order to fill this mold. I think this is going to be our best block so far. We’re combining everything we’ve learned to make a block that’s stronger, lighter, insulating and insect resistant. Another thing we’re doing this time is we’re pouring it in the mold in place. This adobe block we made elsewhere and it cracked as I was carrying it over here to dry. This time we’ll make it right here and we won’t move it around. We should have a stronger block. In about two weeks or so we’re going to test all these blocks that we’ve made and see which ones are the strongest and the best. So stay tuned for our next video.

Naturalhouse’s YouTube channel now with 84 natural building videos.

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