What type of wood must posts supporting permanent structures and resting on a concrete footing in direct earth contact be made of?

Posts that support permanent structures and are in direct contact with concrete footings and the ground must be made of either naturally durable wood or preservative-treated wood to ensure they can withstand moisture, insects, and decay.

Naturally durable wood refers to species that have a natural resistance to rot and insect damage, such as cedar or redwood. This type of wood can effectively endure the stress of being in direct earth contact. On the other hand, preservative-treated wood is infused with chemicals that enhance its resistance to decay and pests, making it suitable for ground contact applications where moisture is prevalent.

Choosing either option allows for flexibility depending on availability and application needs while ensuring long-lasting structural integrity. Using untreated wood in such circumstances is not advisable, as it lacks the necessary protection from the elements and biological threats, which would lead to premature deterioration. Thus, the combination of naturally durable and preservative-treated woods effectively addresses the requirements for permanence and longevity in construction settings.