The panels consist of a three-dimensional frame formed by welded steel rods and a foam core. After installing the necessary number of panels to form the walls, floors, and roofs of a structure and interconnecting them properly a thin layer of concrete is applied to each face to cover the steel rods. The resulting construction is a monolithic reinforced concrete structure composed of walls and slabs of uniform thickness and possessing great strength and stiffness. The cross section of each element consists of two parallel layers of reinforced concrete separated by a layer of foam. The concrete layers are kept together by a truss-like steel frame which has rods going through the foam layers and embedded into both concrete ones. This panels are very efficient from the structural point of view since the resisting material (concrete and steel rods) are arranged away from the center of the cross sections and near the exterior faces where they are most effective resisting flexure such as in slabs. Even for walls that arrangement is very convenient since it reduces significantly the possibility of buckling. From the construction side, this system has many advantages. The weight of the panels is so small that they can be handled and erected by hand without using any equipment. By properly cutting and assembling them, practically any structural shape can be obtained, including curved walls, without using costly form work. The plumbing and electrical systems can be easily integrated into the panels, as well as the window and door frames. The time required to erect and finish the structure is very short, reducing overhead and other costs, and the whole procedure is so simple that it can be mastered by a construction crew in a short time. The performance of this type of structures in service is also outstanding. Because of the sandwich type of construction with a foam core, it has many thermal advantages. Since its reinforcement consists of fairly thin rods closely spaced, the concrete cracking is well under control, resulting in practically crack-free structures, and its monoliths and strength are very desirable qualities to assure a good behavior under wind and earthquake loads. The ratio structural strength versus weight is also highly favorable (better than that for reinforced concrete) and, consequently, the use of this system where the weight should be an important factor to be consider.