According to California Building Code Chapter 15, what is the minimum roof slope required for clay and concrete tile installations?
Correct Answer
A) 2.5:12 (21% slope)
CBC Chapter 15 Section 1507.3.3 establishes that clay and concrete tiles require a minimum slope of 2.5:12 (21%). This is lower than composition shingles which require 4:12, allowing tile to be used on lower-slope applications common in California's Mediterranean-style architecture.
Why This Is the Correct Answer
CBC Chapter 15, Section 1507.3.3 sets the minimum slope for clay and concrete tile at 2.5:12. This is lower than composition shingles (4:12) because tile's interlocking design provides effective water shedding even on lower slopes, making it well-suited for California's Mediterranean-style architecture with lower-pitched roofs.
Why the Other Options Are Wrong
Option B: 6:12 (50% slope)
6:12 is a steep slope and far exceeds the minimum required for tile. While tile can certainly be installed on a 6:12 slope, requiring it would eliminate tile from most lower-pitched California roofs. This value is not the CBC minimum for tile.
Option C: 3:12 (25% slope)
3:12 is higher than the actual minimum of 2.5:12. While tile installed at 3:12 is compliant (it exceeds the minimum), stating 3:12 as the minimum would incorrectly disqualify tile installations on slopes between 2.5:12 and 3:12.
Option D: 4:12 (33% slope)
4:12 is the minimum slope for standard asphalt/composition shingles per CBC, not for clay or concrete tile. Confusing tile requirements with shingle requirements is the most common error on this question type.
Memory Technique
Remember: 'Tile = 2.5, Shingle = 4.' Tile is heavier and interlocks, so it can handle lower slopes. Shingles are lighter and rely more on steepness to shed water. Mnemonic: 'Tile Two-point-five, Shingles Four-to-survive.' The difference of 1.5 between 2.5 and 4 marks the tile advantage.
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