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Note: If you’re new to earthbag building, first read the introductory Step-by-Step Earthbag Building and How to Build an Earthbag Roundhouse .

This Instructable includes complete step-by-step instructions on how to make an insulated earthbag foundation. You can use the same process to make insulated foundations for any type of structure – straw bale, earthbag, cordwood, etc.

Yurts or gers are very efficient and practical in harsh, cold climates, as evidenced by centuries of use in Mongolia. Benefits of yurts include affordability, rapid construction, ease of construction, wind resistance, great looks and portability (ability to take your home with you if you ever move). You may even save on taxes since some jurisdictions do not consider yurts permanent homes.

Many people build their yurts on a raised wooden platform to reduce moisture problems. But wood is expensive and building a platform/deck requires a fair amount of tools and carpentry know-how. Wood is vulnerable to fires and prone to rot and insect damage. It also requires regular painting or sealing. And if the wind and snow can blow underneath like most designs, then you’ll lose a lot of heat.

In addition to the many other uses for earthbags (retaining walls, domes, rootcellars, houses, etc.), you can build insulated foundations by filling the bags with insulation such as scoria. The benefits of the insulated earthbag foundation system described here include:
- Very low cost, especially if you can locate recycled grain bags from farmers
- Very simple construction using just a few tools most people already have
- Save energy and enjoy a more comfortable home because the floor and foundation are superinsulated (with no wind blowing under the floor to suck heat away)
- No deep footings/excavation required (see Frost-protected Shallow Foundations design guide mentioned below)
- The finished floor can be raised above grade as high as necessary. Deep snow? Flooding? No problem.
- Building a rocket stove into the foundation for heating.

For those who live in Canada or similar climates, you might want to follow the Earth-Sheltered Solar Canadian blog , who’s planning to build an insulated earthbag foundation that’s suitable for extremely cold climates.

Building in extremely cold climates uses the same process as outlined in this Instructable, but you will need a deeper trench with additional insulated earthbags below grade to create a Frost-protected Shallow Foundation (FPSF) . Combine these two ideas – FPSF and insulated earthbag foundations as shown in this Instructable – and you’ll have everything you need to know for free.

The following instructions assume you have cleared and leveled the site, removed topsoil, and positioned scoria around the building site to minimize work.

3D AutoCAD drawings show each step of construction.

Step 1: Foundation Trench


Dig a foundation trench slightly wider than your earthbags. Use string or twine attached to a center stake to define the radius of the foundation. Install a French drain to remove moisture if needed, and then add 6”-12” of gravel or rubble, depending on climate. The depth of the trench will also vary according to climate. Consult the FPSF guide mentioned above for more details. For instance, the drawing shows how earthbags can be started at ground level (‘on-grade’) in mild climates. But for cold climates you have to use additional courses of earthbags that start below grade.

Tip: Throw the soil from the trench to the outside. This saves moving the soil later when you berm earth against the sides of the foundation.


Step 2: Insulated Earthbag Foundation


Build the insulated earthbag foundation using bags or tubes filled with scoria or pumice. Other fill materials could be used, but they’re still considered experimental. Scoria (lava rock) works perfectly for making insulated earthbag foundations, because it’s insulating, rot proof, fireproof, and doesn’t attract insects or pests. Scoria is also lightweight and easy to work with. It’s almost like handling bags of popcorn. Buy screened ½” scoria for best results. Place the bags or tubes directly on the gravel-filled trench. Check the radius to each bag so the foundation comes out perfectly round.

Use standard earthbag techniques: barbed wire between courses, tamp and level each course (only light tamping required for scoria), angle bag ends toward center and so on.


Step 3: Fill the Interior Area With Insulation


Once the earthbags are stacked, fill the interior area with insulating fill material such as scoria or pumice. It’s a good idea to use 6 mil plastic sheeting underneath to prevent wicking of moisture.

Step 4: Pour Concrete Slab


Pour a concrete slab on top. Adding another layer of 6 mil plastic will prevent concrete from flowing into the insulation. Note: the slab doesn’t have to be a full 3-1/2” thick like typical slabs, since it will bear less weight. 2-1/2” to 3” thick slabs should work fine in most cases if you use a proper mix, and pour and work it correctly. Get help with this step if needed and/or research how to pour concrete. Plan ahead and raise the floor 5” above any surrounding decks.

Use half inch plywood or, for tighter radiuses, two layers of ¼” plywood to make the concrete forms. Level the top of forms and tie to the stakes with wire.

You could build the yurt directly on the raised slab after sufficient time for curing. This is a good option for radiant floor heating and/or where building with wood is not practical.

The first drawing shows the formwork and the second drawings shows the completed concrete slab.


Step 5: Optional Deck


Optional deck. Use the same building method to create decks around the yurt, although they don’t need to be insulated. Instead of scoria in the bags and under the floor, you can use gravel. Decks can be any size or shape you want. You’re not limited to round shapes, although there are limitations to building high, straight earthbag walls – at some point they’ll require additional bracing. But this is not a concern if you build low earthbag foundations of just a few courses and berm the sides with tamped earth.

It’s best to integrate the deck foundation and main foundation by overlapping bags where walls join. The overlapping bags should be filled with scoria to prevent thermal bridging.


Step 6: Build an Optional Wood Floor


The standard floor method for yurts is to build a circular wood platform that is the same size as the yurt and at least 5" above any surrounding decking. This allows the yurt's side cover to hang down and attach to the circular platform. This method provides a weather tight seal around the edges, added space for floor insulation, plumbing and electrical, and makes it easy to install wood flooring.

The drawing shows floor joists set 24” on center and covered with plywood. Construction adhesive and/or deck screws will help prevent squeaks. You can cover the edges of the wood floor with the concrete forms.

Step 7: Finishing Details


There are two main ways of finishing the sides of the foundation. The quick, easy way is to install 6 mil plastic sheeting around the sides to divert water away. Then berm and tamp earth around the sides and landscape as desired. You could place the plastic sheeting so it goes under the concrete form and slab. The plastic will last for many years if it’s not exposed to sunlight. The longer lasting option is to plaster the sides of the foundation, then add plastic sheeting, earth berm and landscaping. Note how no stairs are required in most cases if you a) design the foundation correctly, b) use decks (multiple levels if necessary) and c) berm the sides.

Now you can set up the yurt and enjoy the benefits of an insulated foundation for years to come.

Here's an interesting application of this insulated foundation that combines an earthbag roundhouse and yurt: Roundhouse with Yurt


I'm curious if you have any suggestions for building on a slope. Is leveling necessary or could you did into the hill and build up with earth bags? Thanks!
We have a massive amount of free info on our websites. This topic is covered on our Natural Building Blog:<br>http://www.naturalbuildingblog.com/stepped-earthbag-foundations/<br><br>You could level the site with heavy equipment of course, but that tends to cost more money and damage the building site more. <br><br>And yes, you can do earth berming against the gravel bags if you add 2-3 layers of thick plastic sheeting to prevent water from seeping into the walls.
<p>Owen, I've been reading over your articles and the are great. My girlfriend and I are thinking about getting a yurt this year and using this foundation with a variation then next year building a second story roundhouse with it. We don't want to pour concrete and are interested in using a pallet floor instead.. I am just not sure exactly how to go about this. Would you place the pallets so that the tops are flush with the highest level of earth bag then build the yurt sub floor on that. or would you fill with scoria flush to the level of the earthbags and install the pallet floor on top? In that case would the pallet floor with floorboards become the yurt sub floor as well? And what about insulation in the pallet floor, more scoria or foam or other? If another type of insulation in between the pallets would you need to use scoria beneath them? Thanks</p>
<p>The main thing is to keep the top of the pallets flush and level as possible. You can put plywood or wood on top for the finished floor. There are lots of ways to insulate the pallets such as scoria, wool, foam packing peanuts, etc.</p>
<p>The main thing is to keep the top of the pallets flush and level as possible. You can put plywood or wood on top for the finished floor. There are lots of ways to insulate the pallets such as scoria, wool, foam packing peanuts, etc.</p>
<p>Hello. Love the very helpful tips. I'm thinking of getting a large yurt and raising it for 2 reasons - possibly as a bear deterrent and also with the idea of keeping some barn animals beneath. Could I use earth bags for a 6 foot height? would I need some central supports? How about an open space (or steel barred gate) for entry/exit and ventilation? Or is this unreasonable?</p>
Of course. You can build 8'-9' high earthbag walls even in earthquake zones. Please read my earthbag Instructables, Earthbag Building.com and search for relevant articles on our Natural Building Blog. Or buy my earthbag ebook to get right to the most concise facts. Short answer: you can do everything you mention if you use the proper building techniques.
I am planning to build a strawbale house. Would this type of floor be suitable? Would it support the weight of the bales or would a different material be better for filling the earthbags for support?
<p>This would work. Earthbag foundations are very popular among natural builders.</p>
Hi Owen, <br>Great post as usual, thanks for that! <br> <br>Could wood pallets somehow be integrated into this design, to avoid using (and paying for) concrete? <br>
<p>Sure. We have lots of articles on building with pallets on our Natural Building Blog. One article is on pallet floors, another one is on pallet flooring.</p>
Is it possible to build a yurt with an earthen floor? I really like the idea of the earthen floors instead of concrete. <br> <br>I know using road base as your fill material the bags or floor would tamp very well and become hard almost like concrete. Will the scoria do the same? <br> <br>I guess what I'm trying to figure out is if I can build an insulated foundation for a roundhouse instead of a yurt.
You can do whatever you want:<br>- insulated foundation for a yurt<br>- insulated floor<br>- tamped earth floor<br>- earthbag roundhouse instead of a yurt<br><br>Scoria is totally different than tamped soil or tamped road base. Scoria is light and airy and will remain loose.
Would cob be an acceptable replacement for the concrete and then just build the berm up around the earthbags???? Would it be destroyed in a wetter area? Theoretically all the water would be diverted UNDER the slab, yes? And then into a french drain if one wanted? I have no engineering/architectural skill, and can't really envision the finished product... so speak slowly and in as few syllables as possible.
Sure. See comment above. Add plastic sheeting under the floor to prevent wicking of moisture. You don't have to use cob (which dries very slowly in humid climates). See this list of 11 earthen floor methods: http://naturalbuildingblog.com/ten-earth-floor-methods/
Owen, you're knowledge and willingness to share with your fellow humans is to be commended. I appreciate all the information you've put out there in respect to earth building. Thank you. <br>
I live in Minnesota, my soil is mostly clay. Volcanic glass/rock etc. aren't found here, what can be bought is expensive and comes in small bags. What else can be used for insulation both in the foundation and in the walls? <br> <br>Thanks!
Sometimes it's easiest to add a layer of insulation on the outside of the finished walls. That's what they do with adobe houses in New Mexico, etc. Then plaster over the insulation or add wood siding.
Is this design primarily for colder climates? Is this design necessary for warmer areas...I'm in TX. Also...do.u put rebar in the concrete?
Yes, insulated floors are for cold climates. If your primary concern is keeping cool, then you're in a hot climate and the insulated foundation would actually be counterproductive. See my recent blog post about earth coupled floors that help keep your home cool without air conditioning.<br>http://earthbagbuilding.wordpress.com/2012/04/06/earth-coupled-floors/<br><br>Use gravel for hot climates.<br><br>No need for rebar or remesh in the concrete since there are no heavy loads.<br>
This is interesting, but it is also permanent and requires permits. I am in Maine, USA. So, here is what I am planning to do. I have a slight sloping area, where I want to put a 16 foot(4.87m) Yurt. I will dig a trench, just deep enough to create a level space for cement blocks and to direct any drainage issues away from the yurt. The holes in the blocks will be filled with sand and the interior of the yurt can also have a sand floor. I am also thinking of building and interior wooden floor. The support structure will be landscape pressure treated wood 3&quot;x5&quot;x8', Probably will use untreated 2&quot;x6&quot;'s for the flooring, so I can minimize the number of support beams. The khana or walls will sit on top of the cement blocks, this should minimize the moisture problems with the frequent rains that we get. Since everything will be portable, no permits will be needed. The town has told me that a platform would require a permit. The interior floor would be constructed in sections, so that would also be portable and not require a permit.
Here's an idea for a very simple design that might get around the codes. Stack one course of earthbags in a circle and then fill the interior with sand or an insulating material such as scoria. Spike the bags in place with saplings to prevent slippage. Berm earth against the earthbags to protect from UV rays.<br><br>Optional: Tamp a 2&quot; layer of subsoil on top to create a temporary tamped earth floor.<br><br>I know it's rather crude, but it's also super low cost, quick and easy. No concrete or lumber required, and it should bypass the codes. Please leave a comment if the code officials say this is okay for a temporary platform.
Hello Owen, I would like to thank you for making these wonderful instructables! I am currently an architectural student, and I am very interested in green/sustainable building. Ever since I've stumbled upon your instructables I haven't been able to stop thinking about earthbag construction! I've even shared the idea with my professor and classmates, thanks for sharing this seemingly perfect building solution!
Thank you very much. You should enjoy my new earthbag book. It's getting very good reviews so far by those who work in the earthbag field. I'll post an announcement on our blog in about 3 weeks when it's available.
I hope these instructions are clear. Someone just emailed me and said they thought the center area was a 'hole.' But as you can see in the drawing above, the center is filled with lava rock (scoria). The earthbags insulate the sides, and lava rock in the center insulates the floor. So the foundation and floor are both insulated.
One small suggestion: If you build this foundation higher -- say 4' or so -- then you might want to fill the lower portion in the center with gravel to reduce costs. There's no need for 4' of lava rock. So again, use gravel in the lower part and put lava rock on the top 1'-2'.

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Bio: Owen Geiger is the former director of Builders Without Borders, a Mother Earth News Green Home Adviser, The Last Straw Journal Correspondent and the director ... More »
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