How much does pressure treated lumber weigh?
Pressure treated (PT) lumber sold in the US is overwhelmingly southern yellow pine — loblolly, longleaf, shortleaf, and slash pine, treated interchangeably and sold under one grade stamp. This page uses loblolly pine (basic specific gravity 0.47, USDA Wood Handbook), the most common of the four, at 8 ft.
Treatment forces a water-borne preservative solution into the wood under pressure, and the wood doesn't just take up the chemical — it takes up the water carrying it. Stock fresh off the treating cylinder commonly runs anywhere from about 35% to 75% moisture content: well above loblolly pine's own natural green-heartwood moisture of 33% (same USDA table), and dramatically heavier than the same board once it's kiln-dried. Left alone, a PT board sheds most of that water over a period of weeks as it dries toward the humidity of wherever it's stored.
The preservative chemicals themselves add little to that: retention — the amount of chemical actually locked into the wood — runs roughly 0.06 to 0.40 lb/ft³ depending on the chemical and the use-class rating, a small fraction of the swing in the table below. Nearly all of the weight difference between a freshly treated board and a dry one is water, not chemical.
Loblolly pine weight by moisture condition, 8 ft
| Size | Kiln-dried (12% MC) | Fresh treated (40% MC) | Fresh treated (65% MC) | % heavier than KD |
|---|---|---|---|---|
| 2×4 | 10.4 lb | 12.0 lb | 14.1 lb | 36.3% |
| 2×6 | 16.3 lb | 18.8 lb | 22.2 lb | 36.3% |
| 2×8 | 21.5 lb | 24.8 lb | 29.3 lb | 36.3% |
| 2×10 | 27.4 lb | 31.7 lb | 37.3 lb | 36.3% |
| 2×12 | 33.3 lb | 38.5 lb | 45.4 lb | 36.3% |
| 4×4 | 24.2 lb | 28.0 lb | 32.9 lb | 36.3% |
| 6×6 | 59.7 lb | 69.0 lb | 81.4 lb | 36.3% |
These are computed from USDA wood-density data at the stated moisture contents, not weighed off real products. Actual store stock varies with how recently it was treated and how it's been stored since. We found no authoritative published per-product weights to cite for PT lumber, so we show the physics instead: the same density model used on every other page, run at the moisture contents PT stock actually carries. See how these numbers are computed.