Underlayment for clay roof tile shall comply with which standard?

The correct standard for underlayment used under clay roof tile is ASTM D 226. This standard specifically outlines the requirements for the performance of roofing felt, which is essential for providing a moisture barrier and protecting the roof structure from water infiltration. ASTM D 226 specifically addresses the absorbency, thickness, and tensile strength of the roofing felt, ensuring it can adequately support clay tiles' weight and resilience against the elements.

The other standards listed pertain to different types of roofing materials or have different specifications that do not apply to the installation requirements for clay roof tiles. For example, ASTM D 225 addresses asphalt-saturated organic felt, which may not offer the same properties suitable for the specific consideration of clay tile installations. Understanding these distinctions is crucial for compliance and ensuring that the roofing system functions effectively over time.