For metal tile roofs, which underlayment option is acceptable?

For metal tile roofs, which underlayment option is acceptable?

• A. 30 pound only
• B. Two plies of 15 pounds only
• C. Either 30 pound or two plies of 15 pounds
• D. 15 pound only

Answer: (C)

Underlayment for metal tile roofs must provide a reliable secondary waterproof barrier. The standard allows either a single 30-pound felt layer or two plies of 15-pound felt, which offer comparable protection in thickness and strength. Two plies give extra puncture resistance and redundancy where fasteners and metal tiles create openings. A single 15-pound layer would be too thin to meet this requirement, while a single 30-pound layer is acceptable but not the only option.

Underlayment for metal tile roofs must provide a reliable secondary waterproof barrier. The standard allows either a single 30-pound felt layer or two plies of 15-pound felt, which offer comparable protection in thickness and strength. Two plies give extra puncture resistance and redundancy where fasteners and metal tiles create openings. A single 15-pound layer would be too thin to meet this requirement, while a single 30-pound layer is acceptable but not the only option.