What Is a Pressure-Treated Pine?

Pressure-treated pine is softwood lumber infused with preservatives to resist rot — the cheapest pergola material, but prone to warping and graying.

Pressure-treated (PT) pine is southern yellow pine forced with waterborne preservatives to resist decay and insects. It is the lowest-cost structural option, but it tends to warp, check, and gray within a few seasons in a humid, freeze-thaw climate, which is why higher-end builds favor cedar, vinyl, or aluminum.