Safe Rooms
A safe room can be incorporated into the construction of a new home, or can be retrofitted into an existing home. And one of the most cost effective systems for building the walls of a safe room are concrete masonry.
The advantage of a safe room over a storm cellar is that the safe room can function year-round as a usable area, such as a bathroom, closet or utility room.
The most inherent danger to people and property during the high winds of tornadoes and hurricanes is the flying debris carried in the high winds. Carried at such intense velocity, items such as 2 by 4’s can become missiles that can cut right through a building wall and endanger the people inside. (1)
The best way to keep your family safe during a tornado or hurricane is to build a concrete safe room inside your home. A safe room is a small, windowless room that is completely encapsulated in concrete - walls, ceiling and floor.
Typically, the room would be located in a central area of the home for additional protection as well as accessibility, but can be placed on the outside wall of the home.
Research
In 2003, Dennis Graber, Director of Technical Publications for the National Concrete Masonry Association, contacted the Wind Science and Engineering Research Center at Texas Tech University to assess the ability of their reinforced wall panels and ceiling systems for above ground shelters to resist tornado forces and debris impacts. Tests were conducted on September 12, 2003. (3)
Texas Tech research demonstrated that both 6 and 8-inch-thick concrete masonry units can resist the impact of 15-lb 2x4 inch wood board traveling at 100 mph.
Six-inch CMU walls that are fully grouted with concrete and reinforced with #4 reinforcing steel (rebar) in every cell can withstand the impact of a 15-lb 2x4 wood member striking perpendicular to the wall with speeds in excess of 100 mph. Eight inch CMU walls should be fully grouted but need only be reinforced with #5 reinforcing steel (rebar) in every fifth cell (40 inches o.c.) for debris impact resistance; however, more reinforcing steel may be required in the masonry wall to carry wind loads, depending upon the design and geometry of the masonry wall. (2)
Many new homes now come standard with safe rooms, usually inside walk-in closets, designed to FEMA standards.
Sources:
- Portland Cement Association. 2011. Concrete Safe Rooms Save Lives.
- Federal Emergency Management Agency. 2008. Design and Construction Guidance for Community Safe Rooms, FEMA 361, Second Edition.
- National Concrete Masonry Association. 2003. Investigation of Wind Projectile Resistance of Concrete Masonry Walls and Ceiling Panels with Wide Spaced Reinforcement for Above Ground Shelters.