To build a bomb shelter, first design an underground room that offers adequate blast protection, continuous airflow, extreme heat protection and enough storage space for a month's worth of food and water. Be aware of local soil conditions, and be sure to design an emergency hatch.
When building a bomb shelter designed to effectively shield human beings from a nuclear attack, use materials of 10 times the thickness normally used for above ground construction, and cover the entire structure in earth to reduce the possibility of gamma ray exposure. Design the blast doors to absorb the shock wave of a nuclear explosion, and dig a trench beneath 3 feet of earth to make room for the roof of the shelter.
Local soil conditions can have a pronounced effect on the ability of a bomb shelter to withstand attack. Soil conditions vary with the seasons, and these conditions can affect the layout of the shelter. A soil test can help determine the holding capacity of the soil and its ability to deflect radiation.
Every bomb shelter should have a non-electric composting toilet and enough bunker beds to accommodate its planned occupants. An emergency hatch is very important since a blast could compromise the main entry hatch, effectively trapping the shelter's occupants if no other means of escape exists.