Tornado refuge area (shelter)
The destruction of structures and threat to life during tornadoes is usually caused by a combination of three factors: Wind-induced forces, Changes in atmospheric pressure and debris (airborne) impact.
There has been enough study on the factors above and there are effective engineering and architectural considerations that can make a building safe during a tornado.
Buildings with heavy masonry and concrete materials that are well tied to other parts of the structure tend to withstand extreme winds. The weight and strength of the walls are able to stop flying debris that often cause damage to property. They also resist the uplift and lateral loads caused by excessive winds, making the building a better refuge area.
Airborne debris move in all directions and refuge areas must have the capacity to shield people from the threat of flying debris. This is why basements are the best places to seek refuge during tornadoes. For building without basements, the lowest roof, first floor, interior or most enclosed places are safer.
Usually, building inspectors can assist you to locate, improve and utilize the best available refuge area, in older and more vulnerable buildings. Long roof spans and large volume open areas such as gymnasiums, auditoriums and cafeterias must be avoided. Also, areas with large expanses of glass and skylights must be avoided.
Make sure you know this preparation tip before a tornado visits. It is a good idea to put “Refuge Area” signs in school or public buildings, because many times, there is very little lead time (The current average lead-time for tornado warnings is 13 minutes) to take refuge.