Since I live in an area that sees Tornadoes fairly often (2014 was the last one) I have been trying to find a building system that will not require concrete for the structure.
Our land is from valley to valley over one of the Boston mountain ridges and bed rock in places is about 2 feet below the surface.
I have been thinking of using this shallow bed rock to our advantage for building a combination Storm shelter/ root cellar for the underground portion.
What we will need to figure out is what will be the best building type for the above bedrock portion.

Our main focus has been on earth bag construction with perhaps a double wall set up for "missile" deflection.

Mr. Hart, as one of the recognized experts in this type of building, will you give me some ideas.
I look forward to reading your book, I know it will be a huge help and great addition to our library of references.

Redhawk

Hi Redhawk,

I think that your focus on earthbags as an approach to building this is good. They are one of the best ways to build underground because they are generally unaffected by moisture issues and can provide very strong retaining walls. There is a good reason why they have been used by the military as barricades against "missiles". You could place the earthbags on top of the bedrock as your foundation.

Reinforced concrete is often used to fashion a bond beam on the top of walls to help stabilize them and provide a good connection point for the roof, but it also possible to make the bond beam with wood or metal, as explained in the book. Cement is used sometimes to stabilize earthen plasters on the exterior, but you can also use lime to do this.

Thank you so much Mr. Hart, for this project I am not against using concrete, just didn't want to have to wrestle with a huge amount of it.

Would an Oval dome be a good choice for roof design in your opinion?
We plan on using a barrier for earthen roofs over the roof and doing a soil cover with grasses to hold the soil in place and make the structure fit into our farm landscape better.

forgot to mention that I will probably be using feed bags for this project since we have collected quite a few of them over the last two years of having AGH.

Redhawk

Oval domes are not as stable at circular ones. I found this out the hard way when I built my original earthbag house in Colorado. The large oval dome over my living room/kitchen began to deform as I approached the top, so I had to completely redesign the structure to incorporate a rigid pole framework to support the oval shape.

I suggest keeping the design circular if you want a dome, and with a catenary shape rather than hemispherical. Also a small dome, no larger than about 15' in diameter, is recommended. Buried earthbag domes larger than this have not been attempted to my knowledge.

Earthbag domes are best employed in rather arid climates, because of the difficulty of insuring a leak-proof barrier. For your purpose you could probably get by with covering the top with a heavy duty moisture barrier before covering it with soil.

Ok, so no oval dome, very good to know so I don't even try that unless I do an internal round wood framework.

I was going to go with a rubber roofing material that seals with a torch. I've used that product on roofs built to also be used as a balcony.

Thank you again, you have been extremely helpful, can't wait to get your book and read it through a few times.

Redhawk