Storms, hurricanes and tornadoes are different beasts, but they share enough similarities that the construction methods to make homes more resilient to destruction from all types of storms are comparable. And as storms ripped through the United States and Ontario saw a weekend of 100 kilometre an hour winds, it’s time to pay close attention to resiliency.
Both hurricanes and tornadoes are “cyclonic” storms with very strong winds swirling in a spiral around a centre. The horizontal “tangential” winds at the outside of the storm are moving at higher speeds, predominately upward, while the winds closer to the center push predominately downward.
Homes near the track of a cyclonic storm see strong winds from all directions. If the eye passes over a home, it will be subjected to winds approximately half the time from one direction and half the time from the opposite direction. At any given time, the windward face of a structure will experience positive pressures while the leeward face will experience negative pressures. The negative pressures are about 20% higher, owing to the aerodynamics of wind rising over and moving around the building.
Hurricanes tend to be more destructive because of their sheer size, which ranges from about 60 miles in diameter up to 1,000 miles. They generate all their force over the ocean, but that force can carry them inland for 100 to 200 miles, and they can persist for several days. Tornadoes are relatively small—on average mowing a path of destruction 300 to 500 yards wide—and relatively short-lived, sometimes lasting only a few minutes. On average, tornadoes move a distance of about 26 miles, usually at speeds from 30 mph to 60 mph, though the largest travel up to 50 miles at speeds up to 300 mph.
In this illustrated resource, we focus on framing methods to resist wind forces.
