6 Things to Consider When Buying Residential Tornado Shelters
Studies show that the U.S. experiences more than 1,000 tornadoes every year, followed by Canada, which records approximately 100 tornadoes annually. Adequate preparation is critical to keeping your property and family safe. Apart from buying food supplies, tornado shelters make the storms more bearable by providing a safe place for you to stay until the tornado passes. When buying a storm shelter, it is important to perform thorough research and purchase one convenient for you and your environment. Some essential factors to consider include:
Certified shelters have been tested multiple times for impact. Also, they are constructed and designed according to FEMA 320, FEMA 321, FEMA 36, and ICC-500 guidelines that ensure the storm shelters protect occupants from the high winds associated with hurricanes and tornadoes. In addition, FEMA reviews its safe room design criteria regularly to align it with the ever-changing weather conditions. As such, shelters with all such certifications are more reliable as they have the proper structural integrity.
2. Design Considerations
Residential storm shelters are designed to withstand different types of extreme loads: wind load, wind-borne debris, and laydown. Tornado shelters, for example, should withstand wind loads 5-7 times higher than similarly sized, non-shelter buildings in the same area. This means the shelters can withstand a 250 mph wind speed design. The shelters should also be tested for resistance to wind-borne debris. Tornado shelters with a 250mph design wind speed, for example, can withstand the impact of a 15-pound piece of lumber flying at a speed of 67 mph on a horizontal surface and 100mph on vertical surfaces. What’s more, the shelter should be designed to withstand the weight of any collapse hazard, laydown, or rollover.
According to FEMA P-361, FEMA P-320, and ICC 500, a storm shelter should provide three square feet per occupant for single and double family dwellings and five square feet per occupant for residential buildings. Other considerations like the amount of time spent in the shelter and if the occupants are planning to use it to store dry goods and other valuables also come into play.
4. Above Ground vs. Underground Shelters
Most residential tornado shelter buyers prefer underground designs when safeguarding against tornadoes. The truth is that above-ground shelters are just as safe as underground shelters. An investigation by The Texas Wind Institute in Lubbock about above-ground shelters on a direct path of the 2013 Moore Tornado found that they held up strong tornadoes like the EF-5 pretty well. The study comprised 13 registered safe rooms and found that all the shelters made it unscathed and the occupants remained safe. Underground shelters have a slight advantage over their counterparts as debris from the hurricane does not affect the sides of the shelter. However, the exit could get blocked, leaving you stuck in the shelter.
5. Construction Material
A custom-built residential storm shelter is made of concrete while a pre-fabricated unit is made of a range of materials including steel plates, corrugated steel, high-density polyethylene, or fiberglass. Pre-built structures such as those made of concrete are more affordable as no building expenses are involved. Fiberglass shelters are the most popular as they are light, affordable, portable, and long-lasting. However, they are more vulnerable to damage caused by external elements like water leaks and mold and can’t resist debris of an EF5 tornado. Also, if you’re living in an area with shifting ground conditions and fluctuating ground temperatures, fiberglass shelters present premature failure. Sometimes, the structures float out of the ground due to the mounting water pressure.
6. Expansion Kits
Tornado shelters should make a provision for expansion, in the event you are hosting more people than anticipated or need to go to safer grounds. Expanding the shelter from its original size needs a new installation checklist and inspection to ensure it provides the absolute protection it is designed for.
Installing tornado shelters is a worthwhile investment if you live in a tornado-prone area. The shelters provide a secure space for your family and any valuable possessions in case of a home invasion. Be sure to use the guide to select the ideal shelter.