After WWII, fallout shelters in basements and backyards, designed to reduce the risk of radiation exposure from a nuclear bomb became popular. Although the government now promotes large community shelters as opposed to family models, the risk of radiation exposure is still a factor, considering over 50 nuclear plants are in operation. Consider some guidelines when building your own shelter.
Choose a below ground area for your fallout shelter if earthquakes and flooding are not a threat. Although above ground shelters are permissible under these conditions, the ground, itself, provides a natural barrier, effectively reducing radiation levels.
Design your fallout shelter to provide space for all the occupants to live for a minimum of two weeks after a nuclear incident, to allow radiation to subside to a safer level. This means designing sleeping and bathroom quarters if no basement living area is available. If you plan to use your shelter only for protection from storms, you may choose to build a smaller model.
Excavate and pour concrete walls to a thickness of 8 inches and reinforce the concrete with steel, in the form of structural rebar. Following national building code is sufficient for underground fallout shelters.
Waterproof the concrete walls of your shelter before you backfill. Purchase a good tar-based sealant and roll it thickly on dried concrete walls to prevent ground moisture and runoff from entering the shelter.
Allow for adequate ventilation. Install a roof fan to release hot air that accumulates in the shelter and provide filtered intakes to remove the largest fallout particles in the air if your shelter is for radiation protection.
Construct a reinforced ceiling in your shelter, covered by 12 inches of soil. If your shelter is large, an engineered steel truss system will provide additional protection from the soil or concrete that will cover the shelter. Pouring a patio on top of the shelter is a popular way to add extra protection. Avoid using the above ground surface as a driveway.
Provide an adequate water source. Experts disagree on the long-term danger from drinking irradiated water but all agree that in the days following a nuclear incident, exposed water sources are undrinkable. Filtering drinking water may not provide adequate protection. Consider installing a distillation unit in your shelter to process water before drinking or washing.
Install a heavy steel door to the entrance of your fallout shelter to deflect radioactive particles. In addition, the safest method of entrance to a shelter is from a door installed flat on the ground with the stairs descending below. Elevated entrances provide less protection from radiation but if one is necessary, pour concrete exterior walls and push soil up around the walls as high as possible.