LINCOLN, Neb. - Nebraskans are no strangers to damage from tornadoes and high winds. But each home damaged by tornadoes and severe storms presents an opportunity to rebuild safer and stronger, say experts from the Federal Emergency Management Agency (FEMA).
During inspections following 1992's Hurricane Andrew, the agency's Hazards and Performance Analysis Group found many damaged homes had foundations, wall systems and roof systems barely connected to each other. "The wind pulled the nails right out," said one member of the study team. "The roofs just lifted off - and then the house is ruined."
According to FEMA studies, the roof is the part of the home which is most vulnerable to wind damage, and the roof design and construction is crucial to a home's ability to withstand the ferocious winds of a tornado. FEMA's wind studies indicate a "hip" roof is better able to withstand high winds than a traditional gable roof. Experts say wind slides over a hip roof as if the roof were a dome; there is nothing for wind to get its teeth into.
It is essential the fasteners between the roof and wall structures in the building should be strong enough to withstand the "uplift" effect of high winds. These wind resistant sheet metal fasteners should be part of the design for new construction or rebuilding an existing roof. Without wind resistant sheet metal fasteners connecting the roof and wall, the new or rebuilt structure may not resist high winds.
In a wind storm like the one which hit Omaha recently, or a tornado, the windows and doors often blow out first say FEMA specialists. When the windows and doors blow out, the wind can put pressure on the roof from below at the same time the wind pulls from the top, creating double pressure on the roof.
One of the "urban myths" about getting through a tornado is to open the doors and windows of the house to theoretically equalize the pressure in the house. But, FEMA mitigation experts say that's wrong. Opening the doors and windows only gives the wind easier entry into the structure.
It is important to insure any reconstruction work meets current state and local building codes. Exceeding the requirements of the building code with a "code plus" approach to rebuilding increases the disaster resistance of the house and decreases the chance of major structural damage from wind.
Here are some tips for protecting property from wind:
Opening Protection: One of the most effective ways to reduce damage to the home is to install protection on the home's openings (windows, skylights and doors), such as impact-resistant windows and doors and/or storm shutters. Purchase or make shutters for all exposed windows and other openings.
Roof Bracing: Roof failures, especially in unbraced gable roofs, are a common cause of major damage to houses and their contents in high winds or tornadoes. Check to see whether the roof framing is braced. If unsure whether the roof is adequately braced, check with the local building department. After inspecting the roof framing, a building official can tell whether bracing is required and if so, how it should be added.
Doors: Exterior doors should be wind and impact resistant or protected with an impact-resistant covering. Many houses are equipped with double entry doors. Because double entry doors span a wider opening than a single door, they are usually not as strong as a single door and are more susceptible to wind damage. Add a heavy-duty deadbolt or replace the existing deadbolt with a stronger one, add side bolts at the top and bottom of the inactive door, and replace the existing hinge attachment screws, in both the doors and the door frame, with longer screws that extend further into the door frame.
Garage Doors: Garage doors can pose problems because they are so large they wobble in high winds which can pull garage doors out of their tracks or make them collapse. If garage doors fail, high winds can enter the home and blow out doors, windows, walls - even the roof. A garage door can be reinforced by adding braces across the back of the door and by strengthening the glider wheel tracks. Hardware and home supply stores, as well as companies that specialize in overhead door sales and installation can provide advice on how to create stronger doors and track systems.
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Source: FEMA - FEMA manages federal response and recovery efforts following any national incident, initiates mitigation activities and manages the National Flood Insurance Program. FEMA works closely with State and local emergency managers, law enforcement personnel, firefighters, and other first responders.