Using the Crawl Space Under Your House
Some homes without basements have "crawl space" between the first floor and the ground underneath the house. If you have this space under your house--and if the house is set on foundation walls, rather than on pillars--you can improvise fallout protection for your family there.
First, get access to the crawl space through the floor or through the outside foundation wall. (A trapdoor or other entry could be made now, before an emergency occurs.)
As the location for your shelter, select a crawl-space area that is under the center of the house, as far away from the outside foundation walls as possible.
Around the selected shelter area, place shielding material-- preferably bricks or blocks, or containers filled with sand or earth--from the ground level up to the first floor of the house, so that the shielding material forms the "walls" of your shelter area. On the floor above, place other shielding material to form a "roof" for the shelter area.
If time permits, dig out more earth and make the shelter area deeper, so you can stand erect or at least sit up in it.
Improvising an Outside Shelter
If your home has no basement, no storm cellar and no protected crawl space, here are two ways of improvising fallout protection in your yard:
Dig an L-shaped trench, about 4 feet deep and 3 feet wide. One side of the L, which will be the shelter area, should be long enough to accommodate all family members. The other side of the L can be shorter, since its purpose is to serve as an entrance-way and to reduce the amount of radiation getting into the shelter area.