You can cover the above-ground portion of the basement walls with earth, sand, bricks, concrete blocks, stones from your patio, or other material.
You also can use any of these substances to block basement windows and thus prevent outside fallout radiation from entering your basement in that manner.
A PERMANENT OUTSIDE SHELTER. If your home has no basement, or if you prefer to have a permanent-type home shelter in your yard, you can obtain instructions on how to construct several different kinds of outside fallout shelters by writing to the U.S. Office of Civil Defense, Department of Defense, Washington, D.C. 20310. There is no charge for these.
When To Leave Shelter
You should not come out of shelter until you are told by authorities that it is safe to do so. Special instruments are needed to detect fallout radiation and to measure its intensity. Unless you have these instruments, you will have to depend on your local government to tell you when to leave shelter.
This information probably would be given on the radio, which is one reason why you should keep on hand a battery-powered radio that works in your shelter area.
If you came out of shelter too soon, while the fallout particles outside were still highly radioactive, you might receive enough radiation to make you sick or even kill you.
Remember that fallout particles can be seen, but the rays they give off cannot be seen. If you see unusual quantities of gritty particles outside (on window ledges, sidewalks, cars, etc.) after an attack, you should assume that they are fallout particles, and therefore stay inside your shelter until you are told it is safe to come out.