However, if 12 inches or more of the basement wall is above ground level, this plan should not be used unless you add the "optional walls" shown in the sketch.
Overhead protection is obtained by screwing plywood sheets securely to the joists, and then filling the spaces between the joists with bricks or concrete blocks. An extra beam and a screwjack column may be needed to support the extra weight.
Building this shelter requires some basic woodworking skills and about $150-$200 for materials. It can be set up while the house is being built, or afterward.
Alternate Ceiling Modification Plan B
This is similar to Plan A, except that new extra joists are fitted into part of the basement ceiling to support the added weight of the shielding (instead of using a beam and a screwjack column).
The new wooden joists are cut to length and notched at the ends, then installed between the existing joists.