## Step 1

Determine the calculated wind speed pressure based on the dynamic pressure formula: P = 1/2 ρ x v^2 where P is pressure in pounds per square foot, ρ is the air density in pounds per cubic foot (lbs/ft3) and v is the air velocity in feet per second (fps). Assume there is a 100 mph wind (146.67 fps) and air has a density of 0.075 lbs/ft3. This is calculated to be 806.7 pounds per square foot.

## Step 2

Determine the maximum designed force a roof can withstand before failure. For instance, assume a residential roof has an exposed surface area of 125 square feet and can withstand 110,000 pounds of force applied to it.

## Step 3

Calculate the maximum force that will be applied to the roof by multiplying the velocity pressure by the exposed roof surface area. This is 806.7 x 125, or approximately 101,000 pounds of force. This means that a roof designed for 110,000 pounds of force should withstand the wind speed.

## Things You Will Need

- Pen
- Paper
- Calculator