Any structural engineers? (vanity)

I recently ran across a web site that sells a frame to bend fence top rail into 20 and 25 foot arches for a high tunnel green house. This got me to thinking about the possibility for using to build a thin shell dome and/or Quonset hut house. I have also run into some articles about how the Japanese have done some research on concrete filled tubes. So put these to together .....

My thought was to build 50' quarter of a circle segments, position them in place to make a high tunnel structure and pump the tubes full of concrete. Much like a Quonset hut that was 50' wide at the arch and say 60 to 80 feet long. The idea is a buried Hobbit house with a large basement. A 50' arch should give me somewhere around 2500 to 3500 main floor and something larger for the basement.

The tubes would be the primary load bearing structures with cross bracing to keep them plumb. Lastly, I would stretch chain link fencing over the structure, back the interior with insulation or screening and shotcrete from the outside. Then sealing against water by spraying Grancrete on the outside after the concrete cures. The final step would be to add dirt to create an earth sheltered home and then finish the interior.

Not a structural engineer, but I’ve done my homework.

You’re actually putting a lot more work into it than you need to.

The “U” beams are a great idea. But all you have to do is cover them with mesh and burlap, then apply the insulation to the inside. Set your skeleton (again, to the inside), then the shotcrete - inside of that.

As far as using wire instead of rebar - I wouldn’t. The actual strength of the arch is in the shotcrete and you want the reinforcement of the rebar.

You don’t have to fill the “U” beams with concrete at all. That and the mesh/burlap only needs to hold until the shotcrete sets up. (The sprayed insulation adds a surprising amount of temporary strength and stability to the structure)

Somebody needs to correct me if I’m wrong, but I don’t think you even need to use the shotcrete on the exterior. Hell, you can pull the “U” beams and burlap off the whole thing after you’re done if you want. (If you leave it or pull it, you still have to seal the structure before you back fill)

It’s really a simple process.

There have been disasters with people burying Quonset huts - but for a spray application of insulation, followed by quick set Shotcrete... it’ll work.

There’s a company that uses balloons to make the forms for underground homes. They spray the Shotcrete straight up to make the dome.

Once the rebar and concrete is in place, the Quonset Hut isn’t even necessary any more. The concrete is the structure. The QH is just a form.

Don’t forget, they make 12’ deep, straight-sided swimming pools with Shotcrete without it slumping. Done in a day.

I’ve seen a simpler process.

Take a backhoe. Dig two parallel ditches between 12-18” wide, about 10-15’ apart. Dig them down about 10ft. Fill with concrete and rebar. Place a slab foundation for the span and thickness and flex design the slab. Cast in place as the floor. After it cures a month, excavate out and reinforce the footings of the piers. Very simple design for a wine cellar.

Throw in some EPDM membrane and geotextile to handle groundwater drainage issues, and install a sump with a french drain as required.

Cast in place stairs or excavate and cast accordingly as one excavates beneath the structure.

Concrete finish on the interior may be influenced by using a visquene 10 mil mylar membrane during he concrete placement for more free formed style concrete subterranean surfaces.

I spent years looking into every conceivable type of alternative construction that exists. Everything from straw-bail, cinder block, a hundred different ideas for underground home, using old beer cans as shingles, building houses out of adobe or glass bottles, rammed earth sheltered homes with old tires... Hell, I even dug into yurts for awhile.

If hubs and I had the money, we’d do underground. Cool in the summer, warm in the winter, and it doesn’t take a lot to deal with mold and moisture issues as long as you address it in the build.

The thing is - with all of these things, you’re going to have to balance cost, with labor, with time.

Now there’s this guy in Texas who had access to Shotcrete - cheap. He also had all of the equipment. He build a freaking hotel out of the stuff - complete with an underground grotto where he hosts weddings.

But he had available materials that the average person simply will not have.

Another guy built a stone house for nearly nothing, but he had access to insulation panels and free labor.

If you’re in our age bracket... the very best thing that you can do is build a house out of 2x6 with spray foam insulation and a very good roof. If you want more security, there are techniques that you can add to the build for very little cost that’ll increase the structural stability of the building tremendously.

Hubs and I *hope* that we can make a reinforced FEMA master bedroom into our safe room. (We spend a third of our lives in that room - unconscious - anyway. Makes sense to make it the safest room in the house)

The thing is, I don’t know how much backbreaking labor you’re willing/able to do. I don’t know what materials you have on hand and how much help you’ll have. I don’t know what resources you’ll have available for a good price.

But when the average person calculates all the factors, the best bet really is 2x6 with spray foam insulation. There’s a reason why that’s the most common building technique today.

If you have the money, check out the companies that build underground homes. There are quite a few. They’ve worked out so many of the bugs for you (including the insurance problem somebody brought up). There are also DIY kits for dome houses that are pre-engineered and safe.

And if you have the resources and the will - play with the other ideas on a smaller scale. Build a small workshop. Put in a root cellar. Make a tiny guest house out of straw-bail. Make a dog house out of slipform stone masonry. Make a short retaining wall for your garden out of bottles and concrete.

One things that these small projects do is drive home the incredible labor that goes into alternative building.

Good luck! Now do your homework and have fun! :)

One more thing - google “earth sheltered home”. You will find more information under that topic of the single most efficient home building technique - for the best price - than anything else. They even break down the water systems and built-in green houses.

So much depends on the geology of the land. In Texas our property was sitting on a solid slab of limestone. Nobody was digging into that. As hot as it was, we didn’t do basements in our area. If you wanted an underground home, you built it above ground, then buried it.

Here in Arizona we’ve got the issue with flash flooding from the monsoon. Again, you just don’t go down. We’re in the desert and smart people still have 36” foundations to stay dry.

Lots of basements, root cellars, and storm shelters in Michigan, though. I saw some ‘interesting’ construction ideas come to fruition on my family’s farms! lol!

(Set a family of men with equipment loose on land with trees and rocks and a ton of ‘garbage’ and see what they come up with over the years... Saw a school bus buried and turned into storage for grain, canned goods, and potatoes. Worked surprisingly well. Also saw an old tool shed set in the ground to be used as a protective chicken coop... that did not go so well. *no chickens were harmed in the experiment.)

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