What is the minimum pitch for a concrete roof system?

What is the minimum pitch for a concrete roof system?

• A. 1 vertical in 12 horizontal
• B. 2-1/2 vertical in 12 horizontal
• C. 1-1/2 vertical in 12 horizontal
• D. 2 vertical in 12 horizontal

Answer: (B)

Water must drain off a roof, and concrete roof systems require enough slope to prevent water from ponding on the surface. The minimum pitch is 2-1/2 inches of rise for every 12 inches of run, which is a 2.5:12 slope (about a 21% grade). Slopes like 1:12, 1-1/2:12, or 2:12 are too shallow to reliably shed water on a concrete roof and can lead to ponding, leaks, and damage over time. Therefore, the minimum pitch is 2-1/2 vertical in 12 horizontal.

Water must drain off a roof, and concrete roof systems require enough slope to prevent water from ponding on the surface. The minimum pitch is 2-1/2 inches of rise for every 12 inches of run, which is a 2.5:12 slope (about a 21% grade). Slopes like 1:12, 1-1/2:12, or 2:12 are too shallow to reliably shed water on a concrete roof and can lead to ponding, leaks, and damage over time. Therefore, the minimum pitch is 2-1/2 vertical in 12 horizontal.