Estimates for the construction of an underground bomb shelter vary, but a mid-range shelter might cost around $20,000. People willing to do the work themselves, however, can likely build a shelter for less than $10,000.
Before constructing an underground shelter, it's important to check out relevant building regulations. While some areas might have regulations dating back to the 1950s or 1960s, when underground shelters were more popular, many underground shelters likely have to meet codes designed for homes. In addition, city, county or state officials might not know which structure category an underground structure falls under, which could lead to time spent in court if an inspector or other official deems a built structure to be unsafe or not compliant.