Different applications impose different hazards on wood, and require different amounts of preservative for protection. These amounts are called “retention levels,” referring to the amount of preservative retained in the wood after treatment. Furthermore, each preservative has its individual retention level for these applications. Be sure to obtain wood treated for the application you have in mind. The intended use is identified on the tag stapled to each piece of lumber.

.25 lbs per cubic foot – Rated for outdoor use above grade only.

.40 lbs per cubic foot – Rated for ground contact. This will work well for joists.

.60 lbs per cubic foot – Used for wood foundation systems- this is required if you plan on burying your support posts in the ground.

.80 lbs per cubic foot – Marine Use: Freshwater Contact

2.50 lbs per cubic foot – Marine Use: Saltwater Contact