The Most Bang for the Buck? Part 1

What’s the most efficient, cost-effective way to build with earthbags? How can you enclose the most space with the least time, effort and money? Well, it depends in part on climate, individual skills and preferences as far as styles/building types. (Other factors will be covered in a future post.)

In general, round shapes are the most efficient. They create the most amount of floor space for a given wall length. This is easily demonstrated by drawing a circle and a square using the same lineal distance of walls. For example, draw an 18’ diameter circle, which will have an area of 254 square feet and circumference of about 56.5’. Divide 56.5 by 4 (= 14.1’) to obtain a square with the same total wall length. A square with 14.1’ per side has an area of about 200 square feet. So in this example there’s a gain of 54 square feet of floor space. (Draw this with your kids. It’s a great learning experience.)

So why do builders churn out square/rectilinear structures? Because modern building materials are rectilinear – plywood, OSB, sheetrock, etc. But we know these materials are energy intensive, costly, lead to monotonous designs and have negative impacts on the environment. Earthbag building frees us from these constraints and enables the use of more efficient round shapes. In addition, round shapes are inherently more stable. “Round is sound” as they say.

Size is also important. Large houses require much more time, labor, skill and materials and can easily wear you down, even more so for owner-builders. It’s far better to build only what you need. You can always add on later. Build with cash one stage at a time.

Another factor to consider is fill material – what goes in the bags. Lightweight materials such as scoria are much faster and easier to use than soil. This one factor alone can cut the labor by severalfold, because scoria is lightweight, easy to work with and requires less tamping. Scoria is insulating and so it’s ideal for extreme climates. Plus, scoria doesn’t rot, burn, attract pests, etc. One limiting factor is it’s less stable in certain applications such as straight walls and tops of domes that curve in too quickly.

And the winner is? I’ll give it a tie between roundhouses and domes, depending on the variables listed above. Small to medium sized roundhouses with simple roof designs have an edge in many cases, especially rainy climates and for those with carpentry skills. In dry climates, domes may be more efficient. Organic shapes that approximate circles are a close runner-up, although this often complicates roof construction.

6 thoughts on “The Most Bang for the Buck? Part 1”

  1. We have a 62 acre property in Ash Fork AZ. It has a fairly dry climate and decent year round weather. We have 6 kids 7-20 years in age. Our plan is to put up a small village of emergency style dome shelters that each cost less than $1000 (In Yavapai county, yo can build an earth structure that costs less than $1000 without building permits). We would design with a lot of outdoor living in mind.

    When we had only four kids, we lived for an extended period of time in a 400 sq ft space in a rainy climate. We have also lived in remote back to the lander situations, so we feel ready for the challenge. as for our property, we imagine creating an outdoor living space, courtyard style, with 5-6 small (10-12′) sleeping pods and then a 26′ diameter tipi for some additional indoor space.

    If you can think briefly about our general idea and game plan and potentially make any recommendations for plans (free or paid) that we can purchase from you, books that you think would be helpful, etc., tat would be wonderful. Also, do you recommend getting our sandbags from cal-Earth?

    I didn’t know about your site until today, so I will dig deeper to see if any of the information I am asking is hidden in one of your info gems. Thank you for your time and energy! We are in the planning stages now ad hope to leave June 1st for a road trip to our property. Once concern for our timing is the monsoon season. any thoughts?

    From my heart to yours Joy

  2. Roofing Materials for round homes?
    So I am wondering what you suggest for roofing in areas where thatch isn’t an option. I like metal roofs especially for rainwater catchment, and abhor asphalt, but I don’t know how I would merge a steel roof to any of the cool circular designs you have. As you pointed out it tends to come in square pieces :)
    Thanks for any input.

    • Options include wood shakes, metal shingles and living roof. We considered buying local wood shakes, but the price was a little steep and would have put us over the $10/sq. ft. goal. You can buy metal shingles or make your own from scrap. Some have used salvaged aluminum printing plates. Tire shingles are another possibility.

      Living roofs are best in rainy climates or else you’ll have too many maintenance problems. This is one of my favorites using a reciprocal pole roof:

  3. Another reason why rectilinear shapes have become more dominant is that if space is confined, such as in an urban location, square shapes natural nest together to either create additional rooms or adjacent buildings.


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