Storm cellar

The floor area is generally around eight by twelve feet (2.4 by 3.7 m), with an arched roof like that of a Quonset hut, but entirely underground.

In most cases the entire structure is built of blocks faced with cement and rebar through the bricks for protection from the storm.

Most storm cellars are accessible by a covered stairwell, and at the opposite end of the structure there can be conduits for air that reach the surface, and perhaps a small window to serve as an emergency exit and also to provide some light.

[1] Fully enclosed underground storm shelters offer superior tornado protection to that of a traditional basement (cellar) because they provide separate overhead cover without the risk of occupants being trapped or killed by collapsing rubble from above.

For this reason they also provide the only reliable form of shelter against "violent" (EF4 and EF5) tornadoes which tend to rip the house from its foundation, removing the overhead cover which was protecting the occupant.

There are the generic underground storm/tornado cellar, also called storm or tornado shelters, as well as the new above-ground safe rooms.

Walls can be provided which form a deflector baffle entry so that the path of the storm debris must touch two impact resistant surfaces before it penetrates into the protected area of the occupants.

TTU engineer Joseph Dannemiller presented the research findings at a TEDxTexasTechUniversity symposium in February 2014.

This unit is put in a hole deep enough to cover the bottom section, and then the excavated dirt is filled in around the top and packed down.