Abstract: To make precast concrete sandwich panels, a first concrete slab is formed having embedded in it one end of connectors which extend from it's surface in two directions with the path between the two containing only thermally insulative material, a layer insulative material is positioned adjacent to a central portion of said connectors to form a solid layer and a second layer of concrete is cast so as to receive the upper ends of said connectors. The connectors provide resistance to shear in at least two directions and include insulative high tensile strength members extending in more than one direction between the concrete slabs.