Core TradesQuestion 152 of 700
The MINIMUM roof slope on which asphalt shingles may be installed (with a doubled underlayment) is:
a.1:12
b.3:12
c.4:12
d.2:12
Explanation
Asphalt shingles may be applied on slopes as low as 2:12, but only with a doubled underlayment because water drains slowly and can back up. A 1:12 slope is too flat for shingles and requires a low-slope membrane roof. 3:12 and 4:12 are valid but are not the minimum.
Law Reference: 2025 CA Residential Code §R905.2.2Practice all 700 questions free — no signup required.
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