The first shotcrete homes were built shortly after the shotcrete process was invented in 1910. In the 1960's a new shotcrete construction panel system was developed. Referred to as welded wire sandwich panels (WWSP), the system has a core of polyurethane or polystyrene insulation sandwiched between two layers of welded wire fabric. The panels, which usually measure about 4x8 feet, are erected and joined on the jobsite, and covered with a minimum of 1.5 inches of shotcrete on both sides.
Maine Built Structures, RI (a division of Shotcrete Systems International, Lincolnville, Maine) estimates it can build a 1,920-square-foot, 3-bedroom WWSP home with a full basement and one-car attached garage for $129,000. When operations expand to other areas, where land is less expensive, the company expects to sell the homes for under 100,000 with lot.
Because WWSP homes have at least 3 inches of shotcrete in their walls, they absorb and retain heat in winter and help keep the house cool in summer. According to the company, the modified, expanded polystyrene core is non-combustible. In addition, the layered composition of the panels is highly resistant to sound transmission, vermin, and intruder entry, and there is no off-gassing that might create health problems.