Wind forces are the most common source of damage to residential construction, sometimes resulting in total destruction. Wind behavior and velocity are influenced by such factors as geographic location, variations in topography (surface roughness), building size and configuration, openings and building stiffness.

The dynamic behavior of wind near the earth’s surface is erratic and unpredictable, many times producing a condition calling gusting. Gusting is the result of sharp or sudden changes in wind velocity which can totally reverse its motion. Most people have experienced leaning into the wind, only to find that upon a gust reversal they are suddenly thrust forward or to the side. Buildings similarly experience reversals in stress, causing members and connections to rapidly switch between tension and compression. Buildings also move and deform under wind force and respond to gusts that change the wind direction by twisting or racking. This results in recognizable creaking noises and can cause nail pops and tears in interior drywall.

Tornadoes represent the most extreme and violent type of wind produced by nature. Buildings are not typically designed for such wind conditions, but are designed according to building codes to handle wind speeds in the range of 90 to 150 miles per hour, depending on geographic location. Why then does so much damage and destruction happen to residential construction buildings during windstorms? Are the building codes inadequate? Are the construction methods inadequate? The answers to these questions will be addressed in the following chapters. First, it is helpful to explain a few wind basics that apply to residential construction.