Rice Hull/Clay Blocks and Earthbags

We’re experimenting with rice hulls and clay to make lightweight building blocks. We’re using 25% rice hulls on our first test block. This is our first test block with a rice hull/clay mixture. This is not the most efficient way to mix it, of course, but we’re just doing small samples. Normally you’d use a pit or a big tarp and mix it with your feet. On my first experiment with rice hull/clay about a year or two ago, I used too much moisture and too many rice hulls. Basically, it was almost all rice hulls with a clay slurry, and it molded. I opened up the bag a month later or so and it was all molded. So I’m using less moisture – just enough to hold it together – and fewer rice hulls. We’re working during the dry season to reduce risk of mold. And in case you’re wondering, humans have been working with fibers and clay, fibers and earth, since the beginning of history, but much of this knowledge has been lost so we’re trying to relearn it. Here’s our first rice hull/clay earthbag. Unfortunately, it’s too wet. I think we have to make another one tomorrow. I think that’s just the way it goes – you just have to keep testing until you find something that works. We just put too much moisture. I made a second earthbag with this rice hull/clay mixture, and you can see it looks a lot drier [note error in video]. This looks pretty good to me. Here are the finished earthbags and block made with rice hull/clay mix. This is to make lightweight walls that also add some insulation.

4 thoughts on “Rice Hull/Clay Blocks and Earthbags”

  1. I am planning to gradually build an eco-resort near Lake Victoria. There are abundant local supplies of rice husk, rice husk and sugar cane bagasse ash, quarry fines and heavy clay. I am therefore very interested in your tests. I have found this link on the web concerning Malawi, to our south. It mentions the use of liquid glass made from hull ash and also the use of it and molasses as stabilisers for adobe blocks and waterproofing plaster and treating thatch roofs. It sound like a dream material. I can find no other references to it on the web. Do you have any experience with liquid glass or molasses? Or can you point me in a direction to look for more info?

    Many thanks

    Tony Simpson

    • Research waterglass. That’s the most common name. I have no direct experience with it, but there’s plenty of information on the Internet. You’ll probably have to do lots of experimenting to create strong blocks. Try to tap into local expertise. See if some of these projects in Malawi are ongoing.

      Putting the mix in mesh tubes or bags though would greatly reduce the need for experiments. Our website has extensive information on building with mesh earthbags. Or use recycled grain bags.

  2. Hey there,

    still thinking how to get a building permit here (Philippines) but first I have a question about the filling material. In our site we have a yellow clay. Its kinda soaking the water when its rainy and gets superdry (with cracklings) during the dry season.
    I think its 100% clay – no black earth or other kind of soil in there…
    Could I still use this for the earthbags without adding anything else to it (like sand, ricehulls etc)?

    Our site is hillside – have you ever heard of an earthbagbuilding which was build into the hill? I was thinking about flattening the area first then start to build the earthbaghouse. After plastering and a finishing layer of cement I wanted to add a waterresistant paint to the wall at hillside then fill the part between wall and hill again. That way the building would be partly IN the hill…

    Im visiting your site/blog and yt-channel regulary – it gave me the idea of creating something like that on my own :)

    Best regards


    • You need to make 1-2 test earthbags. Cut off the bags after they dry and see how they turn out. Are they solid or all cracked? You may want to add sand if they’re badly cracked.

      Read up on building into hillsides. You can do it, but the challenge is preventing moisture problems and slippage.


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