Earthbag Dome Materials Calculator

There is a fun and free online tool for calculating the materials needed for building earthbag domes. I think that it errors on the conservative side, but this is probably a good thing. If you go to you can interact with the calculator.


First you enter the bag size that you plan to use and then the radius of the base. If it considers the size of the bag inadequate for that size of dome, it will warn you about this.

You have the choice of entering how the bag gets filled and tamped to create fat or thin bag heights.

You can control whether the dome has a stem wall, an extra buttress around the base, or how many bags will be placed below grade.

You can also control the ratio of stone, sand, earth  and cement for your fill mix.

And finally, you can enter factors that  will affect the cost of the project.

As you change the various parameters of the dome, the diagram of the dome, similar to that pictured above, will update automatically. This can be a really useful learning tool.

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The Canelo Project

This weekend I had a chance to attend a presentation entitled “Conversations in Clay” by Bill and Athena Steen of the Canelo Project. This happened in Silver City, New Mexico, and was part of a larger Clay Arts Festival.

I have followed the work of the Steens for nearly two decades, as they have promoted natural, sustainable building practices in many ways. The Canelo Project is a non-profit organization that they founded in 1989 with the theme of “connecting people, culture and nature.” The focal point of their work is handcrafting simple, small-scale and comfortable shelter that is built primarily with local and natural materials. They have evolved a unique straw bale and clay wall system that is finished with beautiful clay and lime plasters, sculptural wall carvings, earthen floors and clay ovens.

Many of the projects they have done were in Mexico, where they invited a whole village to participate in the construction. They pioneered the use of light straw-clay blocks for buildings that have more insulation than with traditional adobe blocks. These have the advantage of being much lighter and easier to carry and place on the wall; even children can do this.

You can read more about the wonderful work of the Steens at their website:

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Lowest Cost Earthbag Building Methods

This blog post describes super low cost earthbag building methods that do not have to meet code. These dirt cheap building methods are primarily for those in mild climates (minimal freezing) and low or non-code areas.

Here are some of my favorite low cost earthbag building methods:
– use busted concrete (urbanite) for the rubble trench
– a shallow rubble trench of around 12” deep should be sufficient unless you have expansive soils (in that case consult a local engineer)
– you can skip the rubble trench entirely if you have rocky/gravelly soil or build on bedrock if there’s no freezing
– you can skip the French drain if you’re on high ground that slopes away from the building in all directions and have wide roof overhangs
– use soil from the building site or have sandy/clayey subsoil delivered from excavation companies. There may be some nearby excavation work and find out it’s cheaper to unload at your place than elsewhere.
– use what’s locally available and low cost. For instance, you might want to experiment with rice hull bags if you’re doing a small structure and live near a rice mill.
– buy knitted raschel mesh tubing from Bag Supplies Canada for the best price. Contact Maurice at The last I heard the price was $460.00/ 14-16” loose x 3,000’ (1,000 meters) long. The mesh stretches width wise. This is the size you need to match standard 18” wide poly bags on the gravel bag foundation.
– do as much of the work yourself as feasible. Throw workshop parties with free lunches to help speed the work.
– no barbed wire needed between raschel mesh courses if you build small, simple structures with vertical walls in areas with no hurricanes, tornadoes or earthquakes
– build floors on grade using local natural materials – adobe, sand, stone, etc. with a moisture barrier underneath. Example: see Eleven Earth Floor Methods
– use local poles and wood from the forest or local saw mills
– use earth plaster when practical (wide roof overhangs of around 4’ are recommended to protect the walls)
– trade, barter, scavenge, buy recycled, buy used materials through Craig’s List or local newspaper ads as much as possible.

For many more ideas check out How to Build Dirt Cheap Houses.

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Low Cost Saw Dust Insulation

Guest post from Bob Cromer, one of our readers.
“Here is my idea on low cost insulation.

1) Take a 55 Gallon 6 mil garbage bag.
2) Fill the bag with sawdust, so that it is ~6″ thick when laying flat.
3) Use a thermal PVC welder and close the bag off, leaving roughly 3″ not sealed.
4) Make up a plastic pipe “T” that will accept a shop vac hose with a valve to stop the flow, a 6″-12″ straight piece of plastic pipe with a ladies stocking piece over the end, and a small diameter threaded hose running to a welding Argon tank.
5) Insert the stocking end into the almost sealed bag and evacuate the air from the bag, similar to a vacuum storage bag.
6) Re-populate the Argon back into the bag.
7) Remove the “T” and finish sealing the bag.

My estimate is that bag will have R40 across its thickness. The argon basically increases standard sawdust from R2.5 per inch to over R6 per inch. The cost for this bag will be less than $0.50 each, closer to a quarter.

There will be a lot of uses for this insulation. Sawdust is inexpensive but somewhat heavy.”

Bob Cromer

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The $100 House

Owner-built homes made with locally available materials can be constructed very inexpensively.

Owner-built homes made with locally available materials can be constructed very inexpensively.

A few years ago my girlfriend called me into the living room to see an adobe house on TV. “Quick”, she said, “it only cost $100”. I thought there must be some mistake, but I rushed over to see the house out of curiosity. To my surprise it was quite nice.

The rectangular adobe house I saw on TV looked to be about 13’ x 27’ (351 sq. ft.). It was a simple rectangular home, similar to the photo, with thatch roof. The family had built 99% of everything themselves using local materials. They had even made their own thatch roof panels like these. The $100 budget probably went to things such as hardware.

The main point is you can build very inexpensively if you use locally available natural materials and do the work yourself. This is the main topic on our blog due to the world’s housing crisis. This is how humans provided shelter all through history up until recently. The materials will vary from place to place, so you’ll have to research what works best in your area. Of course, this assumes you’ve chosen an area with few or no building codes. Otherwise that $100 house could very well cost $100,000. But the sad fact is the $100 house might outlive the expensive house and not have all the toxic crap in it.

Image source:
I caught plenty of flak in the $300 house contest for my design entries. Even though my designs were smaller than the one profiled in this blog post, people kept saying it couldn’t be built for that price, yada yada, yada. Of course it can’t if you buy all new materials. But go to developing countries and you’ll see millions of houses built in that price range because poor people have no other choice.

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Underground PAHS House: Stone Wing V6

Underground PAHS house concept: Stone Wing V6

Underground PAHS house concept: Stone Wing V6

“Design on the stone wing concept is being revived after a brief hiatus. My underground home project is growing to include a sunroom / atrium entryway that will give more exposure for PAHS efficiency, and the overall layout has changed drastically to accommodate a larger common area. Check out the attached rough sketch – more to come!”

More drawings at the source: Underground Home Directory

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Modified Arc House

Modification of the earthbag Arc House

Modification of the earthbag Arc House

“An eco-self-build in Australia – there are bound to be hoops to jump through!

“The inspiration for our current plans are largely based on a design by Owen Geiger at the Natural Building Blog. I don’t know if anyone has ever built this house design (whilst plans are available from the site, it’s not clear how many people have purchased each one let alone built it). (more…)

Cast In-situ Adobe T-Bricks

Cast in-situ adobe T-bricks by Vela

Cast in-situ adobe T-bricks by Vela

The blog post the other day about cast in-situ adobe was quite popular and so let’s explore a variation of this method developed by Abe at Vela I consider Abe’s Tblocks a major contribution to the natural building movement – even good enough for a major magazine article. Keep reading to learn the details.

Close up view of cast in-situ adobe T-brick form.

Close up view of cast in-situ adobe T-brick form.

Advantages include no need to buy forms with his method. He made the forms with scrap wood. The interlocking feature creates a strong wall, even though it’s just made with mud. One option for those in wetter climates is to add soil stabilizer to the mix for greater moisture resistance. (Search our blog for keyword ‘stabilizer’ to find previous blog posts.) Now, let’s hear Abe explain how he’s been building with a cast in place adobe method he calls Tbricks.

“We built our first home with cast in-situ adobe using homemade forms that bolt together. Two people can set them up in a few minutes and pop them off just as quickly. We made the form come apart from the sides, so we could use remesh to reinforce the wall.
We eventually migrated to a more refined version, called the T brick. Info on this page:

With regular adobe construction, you mix it, make the blocks, and then cure the blocks for 28 days. Then you make the house. With Tbricks, you pour right on the wall and they cure in place. So you save at least 28 days. You also don’t have to lift the material multiple times, so you save a bit of your back, too. The mixing and pouring will be similar time for both methods.

The Tbricks are faster than bigger forms, like the FORMBLOCK system, because they just slip off after a few minutes after the pour. This also allows you to have fewer forms, because you don’t need enough to make a whole level, just a few bricks.

We liked the method and tried different sizes. It’s deceivingly simple, so you don’t realize the potential until you play with it a bit.

The best form for our adobe was an 8″ thick course, using 1X8 lumber for the form. This makes a 2″ gap between bricks, which you can still fit a hand into to pack the material down. This was the tallest brick that enabled the form to be lifted off a few minutes after pouring without the mud slumping.

Width is dependent on climate, usually 12″ is sufficient. For length, the best way to use this is to make the Tbricks (plus gap) a standard size so that each course is a full set of forms. 1ft or whatever is easiest, 18 inches was the max before we saw the form boards bow a bit. You need to pack the material well in the form.
I never made corner forms, but it could be done. We just used a few scraps to do a quick corner, again, just holding the mud for a few minutes, until it could hold its own weight. Sometimes, we would just stand there holding the corner boards ourselves for a few minutes as we’re taking a break.

It needs to cure for a month or more, that’s really the only drawback. [Note: this time frame could be shortened if you use a stabilizer.]

The T brick molds start out upside down for the first layer. For the next layer, shift 1/2 a brick so that the form is centered over the gap. Pour the brick, wait a few minutes (max 5, I think), then slip the form off. If you figure out your working rate, then you make enough forms that when you pour the last, the first is ready to slip off. Just a guess, this is probably 6 forms or so. The forms move like a caterpillar over the whole course. The forms self-level somewhat, because the side flaps keep it going straight up.

We never did more than 1 course a day, but it could be done, depending on your mix. 2 courses is probably the max per day. We would stick our fingers in the top of the brick to make it really textured to “grip” the next course above.

No cracking, it’s simple to do, and you only need a few forms to get started.

I like it just about as good as anything else. For people that have adobe at or near the building site, it would be easy to knock out a decent room in a week or so. We always did a draining gravel trench foundation with a rock stem wall for adobe, but it’s pretty flexible to fit whatever foundation/site prep you do.

I think the little building in those photos, which became our battery/power house on that place, cost way less than $100. In fact, just about everything on it was scavenged from surplus or junk sources in our area. I bet we had less than $20 in that.
Here’s more photos of it: Flickr

I still have those Tbrick forms, but I haven’t ever used it again, because we don’t have an adobe source here. Those forms are now some 13 years old, and could be used to build a house tomorrow, if needed.

In-situ adobe is the perfect material for someone who has no money, but a little time and effort with adobe nearby. It’s a forgiving material that goes up faster than cob (because the drying/setup times) or regular adobe (which has several months and lots more lifting/moving bricks).

Also, we put up more photos of the Tbricks and also the other styles, which is similar to the formblocks system. These came apart from the sides, but needed a bit longer to set up, but it allowed us to reinforce the wall easily (probably not needed).”


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