What is the dead load of roofing plus water at 2 inches?

What is the dead load of roofing plus water at 2 inches?

• A. 10.4 psf.
• B. 5.2 psf.
• C. 15.6 psf.
• D. 8.0 psf.

Answer: (A)

The key idea is converting a depth of water into a pressure/weight per unit area. Water weighs 62.4 pounds per cubic foot. Convert the depth to feet: 2 inches equals 2/12 = 1/6 foot. Multiply by the unit weight: 62.4 × 1/6 = 10.4 pounds per square foot. So the dead load from water at 2 inches is 10.4 psf. The other options correspond to different depths (for example, about one inch gives 5.2 psf, about three inches gives 15.6 psf, and roughly 1.5 inches gives 8.0 psf).

The key idea is converting a depth of water into a pressure/weight per unit area. Water weighs 62.4 pounds per cubic foot. Convert the depth to feet: 2 inches equals 2/12 = 1/6 foot. Multiply by the unit weight: 62.4 × 1/6 = 10.4 pounds per square foot. So the dead load from water at 2 inches is 10.4 psf. The other options correspond to different depths (for example, about one inch gives 5.2 psf, about three inches gives 15.6 psf, and roughly 1.5 inches gives 8.0 psf).