Abstract: An improved domical structure is disclosed built from thirty identical flat isosceles triangular sections of expanded polystyrene which are further divided into two triangular subsections. The division is from either of the two equal sides of the section to the opposite apex which is bisected into two equal angles. This division creates sixty similar yet unidentical flat scalene triangular subsections of equal height as measured from the largest side which are interconnected by means of a spline joining arrangement in a manner that the dividing line of a triangular section never aligns with the dividing line of an adjacent triangular section thus making a stronger more self supporting shell both during and after construction. The structure is covered both on the inside and outside with a fiber reinforced cementitious structural coating.