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Foam was sprayed over the outer ring wall.
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The foam was then painted to match the airform and
to protect it from sunlight.
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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. |
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The new dome was connected to the existing house by
a thinshell-construction hallway which was framed, filled to the right level
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... and given a rebar-reinforced concrete floor.
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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.
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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.)
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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.
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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.
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Insulating foam layer
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Second layer of reinforced concrete. This was given
a couple of days to dry thoroughly.
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After the plywood was removed from the walls, the
crew started building another set of wooden supports, this time for a flat
concrete roof ...
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... which included eaves about a foot deep on
the outside.
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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.
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Once the concrete has cured,
the roof will be securely supported by the walls and its internal rebar.
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