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.

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