Yes Don, the whole thing is made from sprayed shot crete, except the foundation which is a concrete slab. Mike, it actually has no steel reinforcement at all. It has some 1/4" chain for anchor points and some embedded T-nuts to attach anchors to, but that’s all the metal in it.
Basic procedure: pour concrete slab for floor. Has a basalt rebar ring beam footer and criss-cross of basalt rope for reinforcement mesh. also T-nuts embedded under each one of those 2x4 clamps on the inside and 5 links of chain embedded every 12" around the outside of the air form.
The air form is just a kind of material resembling billboard tarp heat welded together with a hem at the bottom with a rope in it which wraps under the metal pipe ring that is clamped to the floor with the 2x4 clamps. That is supposed to seal the bag to the foundation, but if the concrete isn’t poured well it leaks. So we made a play dough substance with soap and flour and some other stuff (no salt) and packed it in as caulk between the air form and the concrete.
Worked amazingly well.
You air the bag up with a bouncy bag blower and put a manometer in line to regulate the air pressure to about 8 inches of water column which keeps the bag tight.
Frame a form up against the bag for any openings you want, i.e. doors, windows, etc. tape or screw any electrical boxes or solar lights to the bag that you want. We put a bike rim with aired up tire on top an weighed it down for a vent opening at the top. Also, it will serve as access point when I build one of these for a water tank. When you want to remove, you let the air out of the tire and it comes out of the cement.
Then you spray or trowel a layer of concrete on about 3/4" thick. let that set until hard.
The cable over the top is the rigging for the basalt rope that is run back in forth vertically and horizontally to make the reinforcement mesh which hooks on the chain links sticking out of the foundation. Also used a Dewalt hog ring pliers to attach the rope to itself in a few places. 3 or for runs of rope around the door opening. This rigging cable is just a clothesline and pulleys to bring the basalt rope over the structure so you don’t have to handle it much. It’s kind of nasty fiberglass stuff even with gloves.
Then spray another 3/4" or more if you need it to cover the rope. Then trowel around add-ons, it is thicker at the bottom to cover the chains etc, and around the door opening. After that sits 24 hrs you remove the bag and have an earthquake, fire, hurricane, tornado resistant house. But it only has an R value of about .437 so you need to live in Belize or Puerto Rico to not freeze to death in it. Or else insulate with spray on foam…
white wash or paint to seal. install doors and windows etc…
This is different from ferro cement because it has no “ferro”.
I haven’t personally tested it yet, but the trainers who have built these things say they can hold 1000 lbs every 4 feet.
The picture below shows a really bad idea for the door framing, and the access tunnel and the working ladder.
Normally you would build a dormer for the door that would stick out like an igloo door. They were trying to cut a slice off the side of the dome to get the floor area under the building permit requirements and this was the first try at this door frame idea.
The ladder rests on top on a mast pole that is anchored with guide wires inside the air form. I was amazed how sturdy and comfortable it was to work on. Me and Luke both worked on it at the same time and had no problem at all. Most guys not used to construction heights had a hard time being up there and working at the same time. The tires are there to help get it to the top of the air form without dragging metal across the bag.
That picture makes the dome look shorter. It is in a hole behind us. I think the top is 8’7" from the floor.