According to Hawaii Building Code, what is the minimum slope required for roof drainage in areas subject to heavy rainfall?
Correct Answer
B) 1/4 inch per foot
Hawaii Building Code requires minimum 1/4 inch per foot slope for roof drainage to handle heavy tropical rainfall and prevent ponding.
Why This Is the Correct Answer
1/4 inch per foot is the minimum slope mandated by Hawaii Building Code for roof drainage. This slope ensures rainwater moves quickly toward drains and gutters, preventing ponding that can lead to roof failure, leaks, and structural damage — especially critical in Hawaii's heavy tropical rainfall environment.
Why the Other Options Are Wrong
Option A: 1/8 inch per foot
1/8 inch per foot is insufficient for Hawaii's rainfall intensity. While some codes allow this for very low-slope roofs with specific membrane systems, it does not meet Hawaii's minimum for general roof drainage and risks water ponding.
Option C: 1 inch per foot
1 inch per foot far exceeds the minimum requirement. While a steeper slope improves drainage, this value represents a significantly pitched roof, not a minimum standard. The question asks for the minimum, not a preferred or maximum slope.
Option D: 1/2 inch per foot
1/2 inch per foot exceeds the minimum requirement. It provides good drainage but is not the minimum; the code sets the floor at 1/4 inch per foot.
Memory Technique
Think '1/4 for Hawaii' — Hawaii sits in the Pacific and gets a quarter of its name from 'water' in spirit. A quarter-inch slope keeps Hawaii's roofs quarter-clear of ponding.
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