Wood joists or structural floors closer than a certain distance to exposed ground must be made of what type of wood?

Wood joists and structural floors that are close to exposed ground are at a higher risk of deterioration due to moisture and insect damage. To mitigate these risks, building codes and best practices require the use of either naturally durable wood or preservative-treated wood.

Naturally durable wood is sourced from species that naturally resist decay and insect infestation, such as redwood, cedar, and cypress. These woods contain natural compounds that provide a degree of protection against the elements.

Preservative-treated wood, on the other hand, undergoes a treatment process that impregnates the wood with chemical preservatives designed to prevent decay and insect damage. This treatment makes the wood suitable for ground contact applications where the risk of moisture and biological threats is heightened.

The requirement allows for flexibility in material choice to accommodate different architectural designs and budget considerations, while ensuring that the structural integrity and safety of the building are maintained. Using either type effectively addresses the issue of exposure to moisture and offers longevity to the structure.