wall panels include attached angle members 128 adjacent the edge flanges 120 and these provide a flange at right angles to the wall panel so that the edges of the vertical flanges of the channel form members can be fastened temporarily to the angle members 128 by a plurality of fasteners along the height of the arch form member the bottom edge of the arch form member 129 is spaced upwardly from the floor panel 114 by a distance equal to and intended thickness of the floor pad in view of the fact that the arch form members are rigid in structure defined by the two halves each of which forms integrally to legs and the cross piece ensures that the arch form member when bolted together and when bolted to the side walls is rigid and holds side walls rigid and parallel with the side walls now held secure holes are cut in the floor panels at locations immediately on top of the piles 101 so that the top 104 of the pile is exposed through the floor this also leaves reinforcing bars 108 exposed at the top and exposed into or through the floor through the floor is applied a tubular forming member 130 which includes a top portion 131 sitting on top of the floor and a cylindrical portion extending downwardly around the pile so as to provide a connection between the pile and the top of the floor with the arch form members in place reinforcing bars 135 are laid on top of the floor 114 at a height spaced from the floor so as to provide reinforcing bars in the center area of.