Lumber, timber, plywood, piles, and poles that support permanent structures must conform to which of the following standards if they are required to be preservative treated?

Preservative treatment of wood products used in permanent structures is critical for ensuring the longevity and durability of the materials against decay, insects, and other harmful elements. The correct answer reflects the importance of compliance with specific industry standards.

AWPA Standard U1 outlines general requirements for the pressure treatment of wood, including the types of preservatives used and the minimum retentions for different applications. This standard provides essential guidance for ensuring that treated wood meets the necessary safety and performance specifications.

AWPA Standard M4, on the other hand, addresses the specific requirements for the treatment of wood products intended for use in marine environments and other conditions that expose them to high moisture levels. This standard ensures adequate protection against adverse conditions, further substantiating the need for proper treatment specifications.

Both standards are crucial for the appropriate treatment of lumber, timber, and associated materials used in construction, especially when they are to be used in environments where they may be subject to deterioration. Hence, the requirement for preservative treatment falls under both AWPA Standard U1 and AWPA Standard M4, supporting a comprehensive approach to wood preservation in construction.