Our sister site, Earthbag Structures.com, has lots of good information about building with earthbags in disaster prone areas. Click on the link to read the full article. This blog post is just a summary.
Earthbag is very strong in compression (carrying loads) but can benefit from additional reinforcing in key locations, including corners and next to openings, to resist lateral movement. Rebar and mesh can help earthbag walls resist wind loads and earthquake forces. With a thick plaster coating this can become a reinforced shell.
Rebar: When walls reach 1.5 m (60”) height, hammer a 1.5m (5′) long piece of rebar through the corner bags.
Bag: Always alternate bags at corners and stagger joints for strength. As high as possible on the finished wall, hammer a second rebar of the same length in. It will overlap the first. This is the simplest way to strengthen corners of earthbag buildings. [Ideally this rebar is tied into the concrete bond beam.]
Materials: Extra bags and barbed wire
Buttresses strengthen corners without rebar, and stiffen straight walls. Straight walls need a buttress or pier, intersecting interior wall, or a minor corner every 3- 3.5 m (10′- 11′). They also make it easier to add on earthbags to extend houses in the future.
Buttresses can be straight vertical, sloping, curved or stepped. Benches or wider wall bases will also strengthen straight walls if the bags are well woven (interlocked) into the wall. A vertical-edged buttress must stick out from the wall at least 60 cm (24”), and a sloping or stepped buttress 75 cm (30”).
Note: We have lots of articles on reinforcing earthbag structures against earthquakes and hurricanes. I plan to recap some of the most important reinforcing methods in the coming days and weeks, but in the meantime search our sites for complete information. Every website has a built-in search engine.
We plan on building a round earthbag house… With three rooms all being 15′ interior and interlocking… Then covering it with soil on a rubble trench foundation…we r going to build the left and right side to 5′ and raise it as we get to the middle, should be 9′ at the center of the center circle to create our rounded earth roof…then lay on our 2×12 beams for our roof… What if any buttress do u recommend?
Round earthbag structures often do not need buttressing, because the rounded shape is inherently stable.
This is interesting, how can I construct a house useing the long bags. Where will I get them in Cameroon.
If you go to http://earthbagbuilding.com/resources.htm#supplies and scroll down to where there is a list of suppliers for Bags & Tubes you will find some places.
There is much info on the earthbagstructures website, but it has not been updated in several years. I drew the buttress detail, but would not recommend that barbed wire now. Weaving the barbed wire is so much stronger.
Strength comes from a combination of size standards AND construction techniques.
Please check out the just completed Earthbag Options for Nepal online at http://buildsimple.org/resources/EB%20Options%20for%20Nepal.pdf
And see BSI’s simple visual building guides like Building EB Walls Better- we will be updating them soon, but can be found at http://www.buildsimple.org/earthbag.php- follow the link on upper left.
Thanks Patti. I’ll turn this into a blog post tomorrow.
Hey,
kindly mail me a video of an earth bag buttress wall details if you can for we at school in the village/Kenya can understand and implement.
Thanking you in advance,
Rashid.
This is the best drawing that I have. They only have to be 24″ long: https://earthbagbuilding.files.wordpress.com/2012/01/buttress-adding-on2.jpg
Buttresses are very simple. They are short earthbag walls which are perpendicular to long, straight walls. Some people call them piers. They act like a column to brace the long earthbag wall.
Building process: Polypropylene tubes are easier and faster to work with than bags. The key step is to alternate courses of bags on the buttress and long wall to integrate the. Pound 1/2″ rebar down through the buttress for added strength. Remember to use barbed wire between courses of bags.
Here’s another drawing that shows buttresses on a corner: https://naturalbuildingblog.siterubix.com/earthbag-wall-bracing-overview/
It’s good to have buttresses on long straight walls and at corners, although I don’t think many projects in Nepal used corner buttresses.