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. PT is the default lumber for outdoor builds — deck boards, 4×4 and 6×6 posts, joists — so the table covers the treated sizes stores actually stock.
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 — often still visibly soaked on the store shelf — 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. Some yards also sell KDAT (kiln-dried after treatment) stock, re-dried before sale — expect it near the kiln-dried column below, not the fresh-treated ones.
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, Above Ground at the low end and Ground Contact at the high end. A ground-contact board carries more preservative than an above-ground one, but the difference is ounces per board, not pounds — 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.
Is pressure treated lumber heavier than untreated?
Yes, while it's wet. The same 2×4 that weighs 10.4 lb kiln-dried runs about 14.1 lb fresh off the treating cylinder, and nearly all of that difference is water. Once a treated board dries to the same moisture content as an untreated one, what remains is only the retained preservative — ounces, not pounds. Treated lumber isn't a heavier product; it's the same southern yellow pine, sold wetter.