After plywood panels are screwed securely to the joists, bricks or concrete blocks are then packed tightly into the spaces between the joists. The bricks or blocks, as well as the joists themselves, will reduce the amount of fallout radiation penetrating downward into the basement.
Approximately one-quarter of the total basement ceiling should be reinforced with extra joists and shielding material.
Important: This plan (like Plan A) should not be used if 12 inches or more of your basement wall is above ground level, unless you add the "optional walls" inside your basement that are shown in the Plan A sketch.
Permanent Concrete Block or Brick Shelter Plan C
This shelter will provide excellent protection, and can be constructed easily at a cost of $150 in most parts of the country.
Made of concrete blocks or bricks, the shelter should be located in the corner of your basement that is most below ground level. It can be built low, to serve as a "sitdown" shelter; or by making it higher you can have a shelter in which people can stand erect.