Location: Central Texas zone 8a, 800 chill hours 28 blessed inches of rain
posted 4 years ago
While I very much admire what Cal-Earth is doing (and has designed); I really like the simplicity, strength, and added flexibility of an internal framework. I am surprised I don't see more done with Geodesics and earth bag. I have seen a few examples of straw infill with domes; but I think the simplicity of both earth bag and geodesic domes work very well together to give a very strong waterproof structure that is near indestructible. Sarah Yoa's topic on this forum got the wheels of my mind rolling again; and brought me back to this subject. I would be interested in a discussion on what would work/not work on this method, as well as any experience along these lines people here have had.
What I propose is a 6v ( 1/2 or 5/8 ) dome of thin walled square tubing welded; and wrapped in earth tubes (either earth or rice hull.) A 6v dome has almost a smooth radius. It requires more connections but shorter struts. But it makes the shape more compatible with earth bags as it has smoother radius and more support with small spans. It also has a level bottom making traditional foundations easier. A 5/8 sphere reduces the foot print of flooring/foundation material while maximizing interior space.
I am sure most have seen this by now on a dome home in the tropics. He has done an outstanding job on his house; but going through the pictures of his building process there are some issues. First this would never meet any code. (he built on a private plantation in Thailand.) And second, I don't think it has a life span of more than 20 years.
Please don't get me wrong. Steve get's 5 starts for every category: Creativity, Design, and actually DOING it. If I ever met him, he would drink for free. I am just concerned that overtime the settling of the mortar without any structural support on single whythe masonry will be problematic long term.
All this is however achievable with earth bag construction with an internal structure. Buckminster Fuller proved mathematically that the dome is the strongest configuration with the least material. The stumbling block is that the construction material and techniques common to us don't adapt well to anything non rectilinear. But is that not where earth bag excels?
I know most folks don't have a lot of familiarity with welding. It is something of a scary dark magic if you have not done it. However, a MIG welder is cheap, portable and unbelievably easy to use with about 15 minutes of practice. It can be run off a generator on site. It give secure joints and unlimited flexibility of design for window openings and doors. However, one could use less conventional means if they were really opposed. Surplus 2 inch 3/16 wall square tubing can be had for less than a dollar a foot in my part of the country. I just see this as a really good hybrid solution and am having trouble understanding why I am not seeing it done.
I really like this idea... but the main worry that comes to mind is waterproofing. At least for a rainy climate like mine (west coast of canada).
This is pretty much the same thing that put me off of classic geodesic domes... I read about quite a few leak issues. The exceptions seemed(seamed!) to be those that did a full elastomeric coating, like the outside of a monolithic dome.
Possible pitfalls, complications:
What would the outside surface be for this sort of structure, to deal with heavy rainfall?
Would one you expect shifting/settling of the bags over time? How would this impact the outside coating?
Would the interior structure interfere with tamping? How would you tamp the top layers; would the structure need to be built very stoutly to take that force?
While a dome is the strongest structure using the least material for a given volume, a roundhouse has some of the advantage, along with a somewhat more normal roof...
Earth bag domes are shaped the way they are for structural integrity. It is basically a 360 degree Gothic arch.
A geodesic dome on the other hand would have to be built like an igloo. Each bag sculpted and fit perfectly for the structure to hold up under all that weight, almost like a Nubian dome or a dry fit stone arch. The strength of the building would depend largely on the pressure the bags would exert on each other.
I don't know how much weight the internal frame would support, so I would be hesitant to trust it.
Your best bet is to experiment first before putting your trust in something untested.
Build a small out building, a garden shed, anything you are not risking your life in... and then after a year without anything falling down, give it a whirl.
One downside with living spaces like this is the amount of wasted (or dead) space. This is because everything that goes inside (tables, chairs etc) are square shaped and designed for straight walled interiors. So if you are not making your own furniture, then any advantage I see from a dome structure is offset by the inefficient use of interior space.
IMO they work well for other structures where wind or snow loading is an issue, and internal heating efficiency is desired, but as a primary living space I'm not so sure simply because of the massive effort required to make it work.
The geodesic profile is too flat on top, wherein the bagwork is resting and tamping upon framework not bagwork. Need a steeper profile for structural safety, or some really beefy struts.
You could roll or laminate other dome framework, which while admittedly would make earthbag dome construction and attachment issues easier., is not necessary.
The issues of space utilization are important considerations, not aimed necessarily at domes, but rather towards curvy walls and non right angled corners in general. It's an issued addressed by well thought out floor plans, custom built ins, straight sections of wall , etc. you don't write off a curve because it takes an extra day framing up the kitchen cabinets, because when it's done, it's generally a more welcoming space. But they are not for everyone or every situation. However, I see many advantages for an primary living space made from an dome: dirt cheap, durable, healthy, thermal, sustainable housing that , as is true with other good curvy design in general, has a tremendous aesthetic quality that enriches dwelling within. A primary structure, I'd argue, is more appropriate as dome/curvy, then say shed, garage, barn, workshop
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