we build spaces where people gather
Client FTP
concrete thinshell

Concrete Thinshells:
Economical. Beautiful.
Virtually Indestructible.

The structural design is based on the use of an air formed, concrete, thin-shell dome and concrete stem wall. The economy and advantages of this structural system are compatible with construction of assembly buildings like schools, churches and arenas.

The concrete structure is built as follows: /1/ An air form/roofing membrane is assembled in the shape and size of the arena dome using a 31 oz. PVC material. /2/ The air form is attached to the circular concrete ring beam on the stem wall. /3/ Using air pressure, the membrane is inflated to the full size of the dome until the membrane is tight and smooth. /4/ From the inside, the underside of the membrane is sprayed with urethane insulation to a depth of 3" over the entire inside surface of the PVC membrane.

While the urethane is being applied, wire hangers are imbedded in the urethane according to the following: /1/ After completing the urethane application, the hangers are used to attach the steel reinforcing bars to the structure. /2/ The reinforcing bars are placed in the pattern established by the structural engineers design. Small diameter bars are used at the top of the domes and larger diameter bars in the lower parts of the domes. /3/ The reinforcing steel is built up to 4 feet high around the base of the dome and sprayed with shot-crete (concrete with pea gravel aggregate for spraying). This process continues in 4 feet wide bands from the base to the top of the dome. The concrete will be 8"–10" thick at the base tapering to 3"–4" thick at the top. /4/ When the concrete is finally cured, the air pressure is turned off. The construction has become a concrete thin-shell structure with PVC membrane roofing on the exterior.