Earthbag building is probably one of the least technically taxing construction techniques you can choose. You can get away with having no experience whatsoever and still build yourself a strong, sound home. That said, I have seen a few examples of things going wrong, and it’s always the same mistake, so I thought I’d shine a spotlight on it.
Everyone worries about the wrong thing, and I was exactly the same. Most questions come to me concerning foundations, climatic impact on earthbags, and bag fillings. This is probably because folk are at the outset of their build and still planning. Once the construction begins, the questions tend to evaporate in the excitement.
Things not to lose sleep over:
The bag filling is not nearly as crucial as you think it is. As long as you’re using dirt, and that dirt is basically sticking together when wet, you’re going to be fine, (see my article on bag fillings). I did recently spot some birdbrained article by someone who had clearly never laid a finger on an earthbag, claiming you put straw in the bags. Obviously that would be a bad idea. Earthbags are for clayey earth.
Now I’m not saying you don’t need to think about foundations. You do. But we’re all somewhat brainwashed by mainstream building techniques, and convinced the foundations are the linchpin preventing the house from falling down. We’re also certain that that there has to be a concrete slab somewhere, because that’s strong, right?
In fact, a whole bunch of things contribute to the structural integrity of a house. With earthbag building, the foundation is as important for drainage as it is for structural strength. Forget the concrete slab. Forget concrete full stop. It really isn’t what you want or need. Make yourself a nice simple rubble trench with a couple of earthbag rows below grade, and you’ll be fine. It’s simple, effective, and hard to screw up.
The most common mistake is for a wall to collapse.
The most common earthbag issue by far is for a wall to topple. This notably only happens with square/rectangular structures or very large round structures (more than 10m diameter), or retaining walls. So if you’re new to the bagging game, you might want to consider a smaller round house first.
If you’re adamant you want straight walls, then you’ve got to pay good attention to a few things:
1. You need buttresses. And the buttresses must lock into the wall and be attached to the barbed wire of each layer. So you can’t just say, “Oops maybe I need a buttress here,” and add one at the end. It has to be incorporated into the build. This equally true for retaining walls. The higher the wall, the more buttresses you need. A rule of thumb is a maximum of 10 feet/3 metres between buttresses.
2.Your vertical straightness is crucial. With a small round house you can get away with an awful lot. With a square/rectangle, those walls need to be vertical.
3. You need a decent bond beam* to lock the top of the structure together, and on a square structure, that would mean long, straight planks of wood nailed into the top layer of bags.
The logic behind earthbag strength
Every building technique has its own logic, and its own way of supporting itself. With earthbags, the structural strength of the building is created by the ‘tying’ together of everything within the structure using barbed wire. Everything – every bag, every window frame, every door frame, every arch and buttress – must be attached to the rings of barbed wire so that the entire structure is interlocked. This is what really gives it the tensile strength when under pressure of impact or earthquakes, and what stops the walls from toppling over.
If you want to assess whether your walls are liable to collapse, climb on the top of them or give them a shove. If there’s any swaying, you’re in trouble.
Finally, at the end of the build, make sure you have two layers of earthbags going over the top of everything (lintels, arches etc.) Those final two layers create enough pressure and tension to hold the structure together. In most cases you will also add a bond beam* here too.
I know some people are using mesh bags, and I have to be honest, I don’t see how the structural integrity of the building is maintained, especially in seismic areas where the house sways. If someone has actual hard-won experience (rather than hearsay or armchair opinion) of using the mesh bags, please add your findings in the comments below.
*A bond beam is a horizontal reinforcement that runs along the top (or sometimes the middle) of a wall. It holds the wall together and stops it breaking open. In modern mainstream construction, concrete and rebar are used. In traditional building it has usually been thick wooden planks or beams. Don’t assume concrete is stronger. It is brittle, and in the case of an earthquake it can crack. The rebar is the only thing giving concrete any strength. In my opinion, for an earthbag structure, wood is a better option. It has more give, and can move with the house in the case of a quake.
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If you want to know more about the kinds of mistake you can make while building an earthbag house, you may be interested in my most popular book, Mud Ball. This is the story of how I built my own earthbag house, and the various agonies I and the victims I managed to lure into helping me, endured in the process. The ebook is on offer this week at $3.99 on all ebook retailers in all locations (including Kindle, Nook and ibook) so if you’d like to catch it at this lower price, now is your chance. It will go back up to $5.99 on 24th December 2017.
“Despite having very little money, almost no building experience, and endless naysayers who told her she would fail, Atulya K. Bingham completed her lovely earthbag home . . .Her personal, inspirational story shows how anyone can build their own sustainable home with earthbags." Dr. Owen Geiger, author of Earthbag Building Guide and the Natural Building Blog.
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21/12/2017 04:48:12 am
Lifelong dream, home made everything
21/12/2017 02:05:13 pm
It is a dream. And it can be a reality:)
21/12/2017 01:45:06 pm
always so right on= Atulya
21/12/2017 02:05:48 pm
You're such an excellent pioneer Jehane! I await your results eagerly:)
21/1/2019 05:41:02 pm
I completed a small 20ft diameter earthbag studio in the UK using the Hyperadobe (mesh tube) method. If anyone wants wants to ask questions, feel free to contact me through this thread or message me through my FB page.
21/1/2019 11:41:48 pm
I would love to write a post on your earthbag studio Cath. Do add a few photos in our FB group!
25/8/2019 04:22:09 pm
Hey, would love to hear from you!!! You experience is awesome!!!
29/11/2020 08:23:16 pm
I would love to see a foto of your studio if you have any available. I am in the process of completing my first home in Brasil using the hyperadobe (mesh bags) method and have enjoyed the glorious and heinous process of trial and error. My next build will certainly have a few changes.
18/9/2021 11:37:23 pm
It’s been a couple of years but I would love to know how your hyperadobe is doing! I’m considering using it. Thanks.
Hi Cath...hope you don't mind me asking, but how is your earthbag studio ? You live in London...did you need planning permision ?
14/8/2019 10:09:41 pm
Heck ya. we finished ours and had it enclosed by 10 Dec. here. Mid-USA. Temp outside hovering around freezing. The walls were mud plastered but we didn't have them covered in lime plaster. Maybe it was some straw that was in the mud or other contaminate but the mildew showed up almost immediately.
We completed an earthbag house about 7 years ago.
12/11/2022 01:29:13 pm
Ah thanks J. Rice! So sorry I didn't reply before. I sometimes miss the comments. Thanks for your detailed explanation on the mold.And yes you've mentioned something important re: Don't use bleach. It's not the correct solution as you point out. Lime really is the best, non-toxic, cheap and easy way to deal with mold. As well as dehumidifiers or even better wood burners (in cooler climates of course).
24/2/2021 01:27:56 pm
Can a buttress on a square building be considered as the interior wall that is tied to the exterior wall?
12/11/2022 01:29:41 pm
Yes it can.
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