Recently, we built our bathroom addition using adobe bricks.The mixture you use is similar to that which you would use to make cob walls. Unlike cob walls, however — which are constructed using a wet material — adobe bricks are molded wet, then sun-dried to use when they are hardened. For this reason, adobe bricks are much more commonplace in areas which experience hot and dry periods during the year,
Mediterranean regions are one example of where adobe can work well as well as parts of Central America. With bricks, you can build as high as you want in one day, whereas with wet cob, you are limited by how quickly the wall starts to slump under its own wet weight. For this reason, I believe the hot, dry countries take advantage of the drying effect of the sun, and I encourage those living and building in these climates to consider using dry adobe bricks to build structures.
Make Your Own Adobe Bricks for DIY Construction Projects
Build a wooden mold. First, you will need to make a mold using any material available to you, or that you know how to work with. We make ours using wooden boards, but if you worked with metal or plastic, they would work just as well, and possibly be more durable too.You can make a mold to produce one, two, or even more bricks at a time. The limiting factor really is how many you can pick up at any one time in order to drop the bricks out of the bottom of the mold.
So first up, cut your wood to size. When fixing the wood together, you must make sure that each box is as close to square as possible. If they are off even a small amount, this will make it difficult for the bricks to slide out of the bottom of the mold when they are ready. Add a couple of handles on the ends to make it easy to lift when full of clay.
Mix earth material. Next up, collect your earth: A mix of 75% sand and 25% clay works well for us. Some people filter their materials first, but I have found that as long as there are no aggregates larger than a centimeter or so, then its never too much of an issue. You can add straw too, which will help reduce cracking and create a tensile strength within your bricks.
Mix your materials thoroughly! Then add water. The mix should be wet enough to easily mold in to a shape, but dry enough to hold its form on its own. Before you fill the mold, make sure the mold itself is wet to aid expulsion of the brick.
Fill the molds. Throw your mix in to the mold each time with some force, and push it into all the corners to make sure the mold is completely filled out. I prefer to use a slightly wet mix as I can throw it into the mold and it naturally fills all the gaps. But be aware than a very wet mix may slump after you have removed the mold so maybe do some experimenting here to get the feel of different saturations.
When the mold is full, lift it by the handles firmly to release the bricks. You may need to shake the mold slightly to set them free.
Dry the adobe bricks. Then let them dry in the sun, making sure to cover them if you expect rain or extreme heat — fast drying can cause cracks — and turn them every day or two to allow for even drying. You should leave your bricks about a week after drying before using them in order that they harden well.
Build! And when you have enough bricks you can start building. It is estimated that an expert brick maker can make about 300 bricks each day, including collecting and preparing the adobe. After about a week of brick making, we got to a pace where we could make 150 bricks per 10-hour day, including collecting sand from 50 meters away and clay from 80 meters away from our preparation site.
Good luck, have fun, and any questions please email them or leave them in the comments below.
Tom Keeling is based in Portugal and has traveled throughout Brazil and Eastern Europe learning about natural building and farming. He’s working on a two-story stone barn renovation using clay and wood, and including a shower and toilet block built using rammed earth and adobe bricks. Connect with Tom at Fazenda Tomati and on Facebook and Instagram. Read all of his MOTHER EARTH NEWS posts here.
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