In order to minimize cost, only readily available construction materials are employed in the concepts presented. No new technology or unusual building skills are required in construction. Insulating concrete forms may be substituted for the concrete blocks. See Figure 2. The plywood and steel on wood studs concept was developed for retrofitting existing homes with concrete slab foundations.
All construction can occur on either side of the walls of an existing room.
Layers of plywood and heavy gauge sheet-metal are installed on the stud walls in a sequence specific to the wall side selected for retrofit. See Figure 3. This concept requires specific anchorage of wall sill plates to the slab and the walls to the new ceiling joists installed below the existing ceiling. The shelter walls and ceiling structure must be isolated from the surrounding house structure. A number of missile-resistant doors have been developed which withstand the wind forces and stop the design missile.