Pressure treated wood is lumber impregnated with a variety of preservative chemicals to prevent rot and insect infestation in exterior applications like decks and fences. Several species of wood can be treated, but a regionally available species usually predominates in any particular locale.

If you want your dock or deck to be safe, durable, and compliant with local building codes, you need to understand the differences between types of pressure-treated lumber. For example, not all PT lumber is designed to withstand contact with salt water.

Different projects require different types of pressure-treated lumber. Lumber mills ink-stamp each board with a lumber grade. Grades refer to the quality, strength and appearance of the wood. Use when both strength & appearance are important. Use when appearance is not important.

Pressure treated lumber is divided into different types based on the ‘retention level’ or amount of preservative retained in the wood after treatment. The retention level is measured in pounds of chemical per cubic foot of wood (pcf