Preservative Retention Level
The amount of chemical preservative retained in pressure-treated lumber, measured in pounds per cubic foot (pcf). Higher retention = greater decay protection for more severe exposures.
In Detail
Common ACQ retention levels: 0.15 pcf for above-ground use, 0.40 pcf for ground contact, 0.60 pcf for critical structural ground contact, 2.50 pcf for salt-water immersion. The AWPA Use Category system (UC1–UC5) maps exposure conditions to required retention levels.