People build entire homes with earthbags. Why not consider them for building an outdoor shed then? There are little to no downsides, and many advantages. Let's see:
- It's affordable, even frugal. Building with earthbags is a DIY project without high skill requirements. So you save from paying to professional builders first. Then the materials are rather affordable. If you can use earth from your property you'll only need to buy the bags and probably some wood for framing. Read more on this below when we talk about materials.
- There's no building permit required at least in most cases.
- It's easy. Almost everyone can build a shed with earthbags and there are no expensive tools or special equipment required.
- Decent insulation and great thermal mass. This is one of the reasons why people build earthbag homes. The thick walls filled with soil, sand and gravel can keep the inside air from the harsh outside temperatures. More on this in the materials section below.
- Water resistant. Because you'll use polypropylene bags the water resistance of earthbag buildings is much better than this of straw buildings for example (not that many people build sheds from straw anyway).
Building your shed from earthbags is definitely worth considering if you are looking for fun and low-cost DIY way. I am not aware of any companies who offer this as service. But surely you can find someone for hire to help you if you don't want or can't build it all yourself.
Let's talk a bit more about the materials:
Materials and Costs:
OK, affordable. How much? As usual, it depends. At the end of this article I'm giving some links, and you'll see folks build earthbag domes for $300 or less. But it all depends on the materials you choose. Here's what you'll need and what you can choose from:
- The bags. You need to use plastic, non-degradable bags. Polypropylene bags are few cents each, up to a dollar. You can save a lot if you can find used bags from a farmer around you, or misprinted bags from some warehouse.
- The filling. This is really variable. Soil from your property is free if you can dig it yourself. Gravel costs few bucks per ton. You surely have to use some gravel at least for the bottom bags. Sand is few bucks per bag. You can mix sand with soil and gravel too. If you decide your shed need to be well insulated - for example because you want to store food or plants inside - you may consider filling the bags with insulation instead. Then the bags will be lighter too.
- Cement. If you want to do the masonry work with cement you'll have to buy some. But you don't have to use cement. Mud and clay works well too, and can be free.
- Wood material for frames, doors, windows etc. Varies and depends on what you'll have on the shed.
- Some gravel for foundation and something to cover the floor and make it smooth. Maybe water-resist plywood or OSB. Costs $5 - $20 per square meter.
- Roof tiles unless you build with a dome roof. This is possible with earthbags and then even no framing will be required.
Options for materials are plenty so you just need to choose.
How To Build Such a Shed
Like with other sheds you have to start with digging and filling the foundations. But earthbag sheds don't need anything special to support the walls. A typical deck-pier based foundation isn't good for earthbag sheds because it won't handle the weight. More typical solution is to simply dig a ditch so the first row of bags goes slightly in the ground. To avoid sinking in soft soil you can add some gravel in the ditch.
The first 3-4 rows of bags should be filled with gravel to fix your walls well. After that you can fill the rest with sand, adobe, clay, mud, dirt etc. The rest is just arranging the bags to form walls in the shape you want. (See the sources at the end where I'm giving links to detailed building guides.)
Earthbag sheds can be built entirely on the ground like other sheds or they can be partly or fully below the ground level. The latter is often done when you want to build a root cellar.
The roof of your shed can be built from the same earthbags provided they are stacked in dome shape. In the case of square sheds you may decide to build the roof with tiles, or straw, or maybe a green roof. Green roof is hard to make but quite well looking. Check a list of the different shed roofs so you can decide.
The walls should be finished inside and outside. Should you leave the walls naked from outside the sun will destroy the polyethylene bags in less than an year and your walls may start breaking apart. So use mud or cement, or a typical coat and make the walls smooth and protected. It's good to do the same from inside too.
If you want to hang things on the walls you may have to add horizontal wood braces at the time of building the walls so you can spike you nails in them instead of trying to do it in the earthbags. You should do something similar to these guys here who have added supports for an outdoor bench. If you don't do this you may need to attach vertical beams in the ground to support your shed shelves.
To make door or windows you have to add temporary forms from wood so you can stack the earthbags over them. If stacking is done properly in domed shape the support can be removed after that. For rectangular sheds you will need to keep it. And then your door can be made just a regular shed door.
Earthbag sheds require little maintenance as long as you have taken care to protect the plastic bags from the sun. You will need to take care mostly for the wooden parts and the roof.
Are There Downsides?
One major downside was already said - it's hard to hang things on the walls. You can't just spike a nail in the earthbag wall. Perhaps using large treenails works but everything will be secure and stable only if you have embedded wooden beams for this purpose. Otherwise your shelves and all will need to be built on the ground.
Another problem is these sheds can't be easily moved. If you want to move such a shed you'll most probably have to disassemble it.
What Else You Can Build With Earthbags?
It's not just sheds of course. This building technique can be applied to several other types of projects:
- Root cellar. Earthbags are good material because they are thermal mass and protect the crops you store inside from quick temperature changes.
- Chicken coop. For the same reason as above building a chicken coop with earthbags is good.
- Basement. If you have built a house like ours, without a basement, you can build an earthbag basement fully or partly under the ground. Again, the bags being thermal mass is a good thing here.
- Why stop here? People build entire houses with earthbags and it's cost-efficient and eco-friendly way of building.
Sources and More Info
Got you interested on the topic? OK, here are few places to look for more:
- Low-Cost Multipurpose Minibuilding Made With Earthbags - truly awesome stuff by MotherEarthNews. Too bad it's mostly textual description and no many pics.
- Step-by-Step Earthbag Building - and here is one with pictures and very easy to follow. Great instructable! Read the comments as well.
- EarthBag Homes - you're standing on the building materials... is an inspiring collection of projects from all over the world. And they have photos too.
- Plans that employ Earthbags - a big number of mostly large earthbag building plans.
- Earthbag House Plans - that's a whole blog with good earthbag plans and descriptions.