Building a Safe Room: Understanding the Hazard
Almost every state in the United States has been affected by extreme windstorms
such as tornadoes and hurricanes. Virtually every state has been affected by a
"considerable" tornado. All Atlantic and Gulf of Mexico coastal areas in the
United States - including coastal areas of Puerto Rico and the U.S. Virgin
Islands - and coastal areas of Hawaii have been affected by hurricanes. Even in
states not normally considered to be susceptible to extreme windstorms, there
are areas that experience dangerous high winds. These areas are typically near
mountain ranges, and include the Pacific Northwest coast.
What Is a Tornado?
Tornadoes are categorized by the Fujita scale. They typically occur in the
spring and summer months, but can occur at any time in any part of the country.
Tornadoes are sometimes spawned by hurricanes.
Category / Typical Damage
F0 Light: Chimneys are damaged, tree branches are broken,
shallow-rooted trees are toppled.
F1 Moderate: Roof surfaces are peeled off, windows are broken,
some tree trunks are snapped, unanchored mobile homes are overturned, attached
garages may be destroyed.
F2 Considerable: Roof structures are damaged, mobile homes are
destroyed, debris becomes airborne (missiles are generated), large trees are
snapped or uprooted.
F3 Severe: Roofs and some walls are torn from structures, some
small buildings are destroyed, non-reinforced masonry buildings are destroyed,
most trees in forest are uprooted.
F4 Devastating: Well-constructed houses are destroyed, some
structures are lifted from foundations and blown some distance, cars are blown
some distance, large debris becomes airborne.
F5 Incredible: Strong frame houses are lifted from
foundations, reinforced concrete structures are damaged, automobile-sized
missiles become airborne, trees are completely debarked.
Not all parts of each state are at equal risk from tornadoes. For example,
while Texas has the highest number of recorded tornadoes, the state's least
tornado-prone area-along the Gulf Coast-has been hit by fewer tornadoes than
northeastern Arkansas. Comparing the numbers of tornadoes recorded in different
areas within a state can give you a better understanding of the potential
tornado activity in those areas.
What Is a Hurricane?
Hurricanes are categorized by the Saffir-Simpson scale.
Category / Typical Damage
C1 Minimal: Damage is done primarily to shrubbery and trees,
unanchored mobile homes are damaged, some signs are damaged, no real damage is
done to structures.
C2 Moderate: Some trees are toppled, some roof coverings are
damaged, major damage is done to mobile homes.
C3 Extensive: Large trees are toppled, some structural damage
is done to roofs, mobile homes are destroyed, structural damage is done to
small homes and utility buildings.
C4 Extreme: Extensive damage is done to roofs, windows, and
doors; roof systems on small buildings completely fail; some curtain walls
fail.
C5 Catastrophic: Roof damage is considerable and widespread,
window and door damage is severe, there are extensive glass failures, some
complete buildings fail.
In the United States, 158 hurricanes were recorded to have made landfall
between 1900 and 1996. Hurricanes have made landfall in Florida more than in
any other state. The second most hurricane-affected state is Texas, but every
state on the Gulf Coast and bordering the Atlantic Ocean, as well as U.S.
island possessions and territories, are susceptible to damage caused by
hurricanes.
In recent years, the U.S. territories of American Samoa and Guam have been
seriously affected by numerous tropical cyclones.
Building a Safe Room
A safe room may be designed and constructed to meet all applicable FEMA criteria. However, use of the
safe room during a hurricane may not be in compliance with mandatory evacuation orders of the local
jurisdiction. FEMA recommends that all safe room occupants comply with local jurisdictional directions
and orders during a hurricane event (which may include evacuation) even if they have constructed a
safe room.
Warning: A safe room designed to protect you and your family or employees from a hurricane or tornado should not be built in an area expected to be flooded during a hurricane, thunderstorm, or other severe weather event. Residents of hazard-prone coastal areas should abide by the warnings of their local emergency services personnel and evacuate to safer ground. The protection from wind provided by safe rooms and shelters is quickly negated when people find themselves trapped and inundated by floodwaters. If you do not know whether your home or small business is in a storm surge area or other
area subject to flooding, check the community service section of your local phone book for storm surge evacuation information or ask your local emergency management or floodplain management official.