We get quite a few enquires about vaults. So far we’ve always cautioned against building earthbag vaults except for small entranceways, corridors between domes and the like, because they are inherently unstable if you just stack earthbags into a vault shape. The proposed design shown here resolves the stability issues. This vault building method is very strong, simple, low cost, superinsulating and extremely fast and easy to build. The shell of a small, simple vault could be built in about one week, in part because the top two-thirds of the vault is built with tubes or bags filled with lightweight insulation such as scoria or pumice (preferably nonflammable materials). In summary, the weight is low in the walls for stability, and the upper part is made with bags or tubes of insulation tied to rebar or bamboo. Note: a catenary vault is shown, but you could also build a pointed vault to expand roofing options.
Options:
– thick cement or lime plaster: straight forward, but plaster will get ugly mold in rainy climates
– cover plastered vault with eucalyptus poles and thatch (use pointed vault)
– arched bamboo instead of rebar is possible if it’s soaked in borax solution and/or smoked
– add joists (which act as cross braces) and a loft, ex: bamboo poles and split bamboo
– join multiple vaults side by side
– extend the vault to create protective overhangs on the ends (good for Thailand)
– screen the top of arched ends for max ventilation (area above windows and doors)
– stone around the base for improved moisture resistance and reduce splashed mud
– earth berm at base
– pipe trusses joined with flat strips on the bottom to distribute the weight and then set on top of the vault and covered with ferrocement and a living roof (cover of Art of Natural Bldg. look!)
– corrugated metal roofing run horizontally (easy to bend over the top but creates harsh look that’s not beautiful)
– build a pointed vault with corrugated metal roofing run vertically
– horizontal slats tied to vault with corrugated metal roofing or recycled metal scraps
Tomorrow I’ll post my insulated vault design for rainy climates.
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what’s the span in this concept? This would make a great barn, with a loft up high for hay storage…. and I need a barn….
The loft is 9-1/2′.
and the span on ground level?
12-1/2′
vaulted torus home with courtyard!
i’ve been dreaming of a design like this forever.
I’ve heard of torus shaped (doughnut) houses, but never using vaults. That’s a new one. You could build your dream now. However, larger spans will require more reinforcement than just simple arches of rebar.
Please spread this blog post about earthbag vaults so it reaches a wide audience. I think this is one of the more exciting earthbag developments lately. Earthbag domes and roundhouses are extremely popular, and now there’s a good way to build simple low cost vaults. The more I think about it, the more I want to build one of these babies — sooner rather than later — because you get a lot of bang for the buck.
One could possibly revert to a dome that was less pointy?
Rounded domes made with all earthbags would not be stable. Try it out and you’ll see the bags will tilt out of balance and collapse. But you can use rebar like with the vault and round the top this way. (This will be covered in a future blog post.) The one I’ll post in a few hours shows a pointed vault with roof for rainy climates.
I’d like to add Basalt Fiber Rebar. It still uses a resin material, but is less horrible than steel rebar. Plus, it doesn’t block or induce magnetic fields (where the application might concern), nor does it rust. Since it doesn’t rust, none of the associated destructive failures of reinforced concrete apply, either. A concrete structure can be made thinner since exposure to oxidizing elements is no longer a concern. Less concrete is always good….
It also tends not to bend willingly. It is supplied in rolls and it very light weight. You could bend basalt rebar into an arch, which it would hold on it’s own. Kinda like building a cheap PVC pipe greenhouse. Throw the mesh over that, just like a cheap PVC greenhouse. Then add the bags… Maybe the mesh could be storm fence?
You could use storm fence, but it’s probably more expensive than chicken mesh, etc. and stronger than you need. Another option is plastic mesh, which is about the same cost as metal mesh and it won’t rust.
The recent blog post about Lunar Earthbag Structures http://earthbagbuilding.wordpress.com/2011/07/07/lunar-earthbag-structures/ sparked a private discussion with fellow earthbaggers. We all agreed the vaults in Mandeep Singh’s thesis are not very stable. But his paper got us thinking again about ways to build more practical earthbag vaults. I thought to myself “what would I do?” (Patti Stouter had the same thought.) I would use typical earthbags low in the wall for strength and stability, add arched rebar every 2’ or bamboo, attach plaster mesh and tie lightweight bags of insulation on top. This would be a very simple, practical solution.