A proper tornado-resistant design protects a home’s integrity and its occupants. The design must take into account the strength of the entire house, provide a continuous load path, and be impact resistant. FEMA, however, still highly recommends a safe room, or tornado shelter, for maximum safety to a home's occupants during a tornado emergency.
"Tornadoes have become more disastrous than hurricanes and earthquakes in North America. Having a home built with ICF walls solves that. Aside from that, when it comes to home renovations, contrary to what most people think, ICF homes are also easy to work with” - Chuck Waltman, Home Remodeler.
A Continuous Load Path for a Tornado Proof House
When the severe winds of a tornado try to rip a house apart, a continuous load path is the best defense towards holding the home together. The continuous load path ensures that when a load, including uplift and lateral (horizontal) loads, attacks a home, the load will travel from the roof, wall, and other elements toward the foundation and into the ground.
In addition, the integrity of the walls, roof, and floor are critical to ensuring a strong continuous load path that will hold the home together during a dangerous tornado.
Strong Tornado-Resistant Wall Systems
Building failures during tornado events often start with damage to the roof. First, the wind blows the shingles from the roof sheathing. Then, the roof sheathing rips from the roof framing. Finally, the roof framing pulls from the supporting walls.
A tornado-resistant roof’s primary function in a continuous load path is as a horizontal diaphragm that moves the loads imposed by heavy winds to the supporting walls below. The roof sheathing is the first structural element in the load path between the roof system and the foundation. The sheathing works with the roof framing to transfer lateral loads to the home’s shear walls.
Roof framing is the next building element of the load path. Sizing of the rafters of a roof’s frame must resist the weight of the roof system. The roof framing must also move the lateral loads to the shear walls below. It is essential in tornado-resistant roof design that the roof sheathing and framing are built and sized for the potential wind forces of the specific region.
Solid Tornado-Resistant Floor Construction
The floor system is the part of the continuous path that moves the loads to the shear walls in the stories below or the foundation. Floor framing often consists of dimensional lumber, or floor joists, spanning an open space. Floor joists must be sized to withstand the loads of the entire floor system along with vertical loads. The floor of a tornado-resistant home ensures the loads meet their final designation - the ground.
A tornado-resistant design protects a home’s integrity and its occupants. Critical to tornado-resistant home design is a continuous load path, impact resistance, and strong roofs, walls, and floors. A safe room, or tornado shelter, is also highly recommended for the maximum safety of a home's residents during a tornado emergency.
