How-to Earthbag Construction
Check out our How-To Foundation Video
Earthbag construction is a great way to add mass to your Earthbench while experimenting with another method of natural building. Again, there are other ways to create mass for your bench height (stacking rocks or urbanite, using cob and bottle bricks) but Earthbag construction is a simple and fun method. To read more about Earthbag construction, check out the Wikipedia site.
The basic concept of Earthbag construction is making a moist mix of clay and sand, adding this mix to polyurethane plastic sand bags, sealing off the sand bags, and then tamping them down on top of your rock foundation. These are the main steps:
1) Mix clay and sand together using a tarp or a wheelbarrow. Ratios will vary depending on how sticky your clay is. Typically you want more sand to clay - you only need enough clay to bind the sand together. A typical Earthbag ratio is 1.5 or 2 parts sand to 1 part clay. If your clay is very sticky, more sand will be needed. If it is not very sticky at all, a 1 to 1 ratio may be fine. If your soil is very sandy to begin with, you can just use straight soil.
2) As you mix the clay and sand together add a minimal amount of water. If you add too much water, the mixture will become too sloppy for proper Earthbag construction. You just want enough water to activate the clay and help bind the mixture together. You should be able to form a "ball" with the mixture but - when you throw it up - it should crumble. You will know you have too much water if - while tamping down the bags - they "bleed" out a lot of extra water.
3) Once you have the right Earthbag mix, add the mixture to polyurethane plastic sand bags (you can find these at flood control centers or home improvement stores). The larger bags are typically better. Fill up the bag almost to the top, but leave enough room so that you can fold over the top of the bag two times over and use two nails to "sew" the bag shut. Stick the nail through one side of the fold-over, and then stick it back through the other side. Two "sewed-in" nails on either side of the fold should be adequate (check out pictures below if you are confused).
4) Add the Earthbag to your rock foundation and use a tamper to tamp it down. You can buy a plumbers tamper at a home improvement store or you can be creative and make your own tamper! (see photo above). If you don't have access to a tamper you can use a large flat stone (like a large piece of urbanite) to tamp it down. Make sure to leave at least an inch of the top of the perimeter rock exposed as foundation by which you can add cob. (don't let the Earthbags flop over the perimeter rocks)
5) Repeat this method until you have enough mass for your bench. You may need to do two layers or more of Earthbags to gain the right height. In traditional Earthbag construction you use barbwire between Earthbag layers to prevent movement. But for two or three layers of Earthbags this may not be necessary. Ideally you should let the Earthbags dry for a day or two before you cob. They should dry nice and hard.
Earthbag construction is a great way to add mass to your Earthbench while experimenting with another method of natural building. Again, there are other ways to create mass for your bench height (stacking rocks or urbanite, using cob and bottle bricks) but Earthbag construction is a simple and fun method. To read more about Earthbag construction, check out the Wikipedia site.
The basic concept of Earthbag construction is making a moist mix of clay and sand, adding this mix to polyurethane plastic sand bags, sealing off the sand bags, and then tamping them down on top of your rock foundation. These are the main steps:
1) Mix clay and sand together using a tarp or a wheelbarrow. Ratios will vary depending on how sticky your clay is. Typically you want more sand to clay - you only need enough clay to bind the sand together. A typical Earthbag ratio is 1.5 or 2 parts sand to 1 part clay. If your clay is very sticky, more sand will be needed. If it is not very sticky at all, a 1 to 1 ratio may be fine. If your soil is very sandy to begin with, you can just use straight soil.
2) As you mix the clay and sand together add a minimal amount of water. If you add too much water, the mixture will become too sloppy for proper Earthbag construction. You just want enough water to activate the clay and help bind the mixture together. You should be able to form a "ball" with the mixture but - when you throw it up - it should crumble. You will know you have too much water if - while tamping down the bags - they "bleed" out a lot of extra water.
3) Once you have the right Earthbag mix, add the mixture to polyurethane plastic sand bags (you can find these at flood control centers or home improvement stores). The larger bags are typically better. Fill up the bag almost to the top, but leave enough room so that you can fold over the top of the bag two times over and use two nails to "sew" the bag shut. Stick the nail through one side of the fold-over, and then stick it back through the other side. Two "sewed-in" nails on either side of the fold should be adequate (check out pictures below if you are confused).
4) Add the Earthbag to your rock foundation and use a tamper to tamp it down. You can buy a plumbers tamper at a home improvement store or you can be creative and make your own tamper! (see photo above). If you don't have access to a tamper you can use a large flat stone (like a large piece of urbanite) to tamp it down. Make sure to leave at least an inch of the top of the perimeter rock exposed as foundation by which you can add cob. (don't let the Earthbags flop over the perimeter rocks)
5) Repeat this method until you have enough mass for your bench. You may need to do two layers or more of Earthbags to gain the right height. In traditional Earthbag construction you use barbwire between Earthbag layers to prevent movement. But for two or three layers of Earthbags this may not be necessary. Ideally you should let the Earthbags dry for a day or two before you cob. They should dry nice and hard.
