I want to construct a 15m diameter, frequency 3, 4/9 truncation geodesic dome entirely of thick walled (ideally 200-300 mm S grade Polystyrene) panels. The panels will be longitudinally finger jointed (a sinusoidal wave pattern of 25mm depth) along their edges so that once the dome is completed a single panel would be mechanically held in place and could not be dislodged even if there was localised failure of the
bonding adhesive (expanding urethane foam). The domes inside and out will be sculptured to a sperical surface. The dome will be covered in a light stainless mesh with high tensile wire reinforcing (also anchored to ground anchor points) and the dome will be plastered with the standard treatments used in monolithic plastered polystyrene house construction

Can anybody conjecture what thickness of polystyrene is sufficient without any steel substructure? (on the basis that polystyrene is much lower cost than steel so if the structural component can be constructed entirely of polystyrene this may make economic sense.

Would constructing the dome with thicker sections toward the base add significantly to strength and if so what proportion of thickness versus height would a respondent recommend.

Cheers