Further Shell Construction

Protecting the Ring Wall
Because of sloping ground on the building site, the new dome is built on a dirt-filled ring wall which is up to three and a half feet tall at the low point of the slope. This wall got additional insulation to protect it from temperature changes.


stem wall insulation
painted insulation
Foam was sprayed over the outer ring wall.

The foam was then painted to match the airform and to protect it from sunlight.
Connecting the New Dome
Two living room windows in the original design were turned into a wide hallway opening to give us access to the new dome. The connecting hallway, made with straight walls and a flat ceiling, was built much like a standard Monolithic structure but with plywood supports instead of a pressurized airform. At first glance it seems that working in normal air pressure would be easier, but in fact it made the job much more complex.
connector 1
connector 2
The new dome was connected to the existing house by a thinshell-construction hallway which was framed, filled to the right level ...
 ... and given a rebar-reinforced concrete floor.

connector 3
hall form
Rebar was placed in the wet foundation concrete to tie the floor and walls together. Notice that there are two lines of rebar; the wall will be made of two layers of concrete with foam insulation between them.
The shape of the hallway walls was defined by sheets of plywood supported by wooden bracing. (This is the job normally done by a pressurized airform.)
hall wall rebar
hall window frame
First layer of rebar inside the wall, ready to go. Note the wooden lintel at the top which creates a solid top on the wall just as was done with the ring wall around the foundation. One of the two existing living room windows was removed and replaced with plywood (left) before the windows were covered to protect them from sprayed concrete.
A 4 x 3 foot window for the hallway was formed exactly as it would be in a standard dome shell, by framing with pressure-treated wood and not filling the frame. The extra piece of rebar at left will connect to the second layer of concrete and rebar after the middle layer of insulation is sprayed.
hall foam
hall layer 2
Insulating foam layer
Second layer of reinforced concrete. This was given a couple of days to dry thoroughly.
roof 1
roof 2
After the plywood was removed from the walls, the crew started building another set of wooden supports, this time for a flat concrete roof ...
 ... which included eaves about a foot deep on the outside.
hall bracing
hall roof rebar
The plywood form for the roof was VERY solidly braced from inside to support the estimated weight of 7600 lb (two cubic yards) of wet concrete.
 Once the concrete has cured, the roof will be securely supported by the walls and its internal rebar.

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