Budget underground shelters are available from SurvivalCenter.com. The shelters require some assembly, although turnkey options are also available. The budget shelter consists of a steel tank that measures 8 feet by 20 feet. The tank includes an entrance port, two small air ports and lifting hooks. Optional extras include ladders, flooring, shelves and bunks. The shelters can be connected to create underground complexes with multiple entrances and exits.
Some people opt to build their own underground shelters from scratch. Earthbags, which are large polypropylene sacks filled with dirt, are an inexpensive option. The bags are stacked like bricks and secured with barbed wire, a technique that can create walls strong enough to pass California's earthquake tests. Earthbag shelters that sit fully underground should be built in dry, well-drained soil. To save the time and cost of excavating, some earthbag shelters are situated partially underground or are built above ground and covered with dirt.
Other underground shelter options include mini shelters made from galvanized road culvert, fiberglass shelters that are impervious to radar, and a range of blast-hardened steel structures that are ready to be buried. Other companies offer reinforcement options for existing houses, including underground rooms. For larger groups of people, decommissioned missile silos occasionally come up for sale around the United States.