Pressure-Treated Wood Weight Calculator

In 2026, a deck contractor framing a 24×16 ipe-over-PT deck in coastal Florida orders 12 wet ACQ 2×8×12 joists from the lumberyard. Each joist weighs 33 lb fresh from the cylinder vs 22 lb untreated — and the crew lead needs to know whether the boom truck can stage the full order safely. This calculator translates the AWPA Use Category 4A retention specification into a real-world load weight.

The modern era of pressure treatment begins with John Bethell's 1838 British patent on creosote pressure injection — a process developed to extend the life of railway ties in damp British soils. Bethell's closed-cylinder method (vacuum, flood, pressurize, vacuum again) remains the basis of every commercial pressure-treatment cycle today, including modern waterborne preservatives.

Through the 20th century, the American Wood-Preservers' Association — founded 1904, now AWPA — codified the standards for treatment processes, retention levels, and quality control. AWPA U1 (Use Category System) and T1 (Treatment Process) are referenced by every U.S. building code, including the IRC and IBC. The standards specify minimum retention in pounds-per-cubic-foot (pcf) of preservative chemical.

CCA — chromated copper arsenate — dominated residential pressure-treated lumber from the 1970s through 2003. The familiar greenish tint of older PT decks comes from copper. CCA gave way to ACQ (alkaline copper quaternary) and copper azole formulations after the EPA, citing concerns about arsenic leaching from playground equipment and direct skin contact, ended residential CCA registrations effective December 31, 2003. Industrial CCA remains permitted for utility poles, marine pilings, and bridge timbers under 40 CFR 152.32.

ACQ became the dominant residential preservative from 2004 onward — it's 70-80% of the market. MCA (micronized copper azole) entered around 2008, using particulate rather than dissolved copper, which reduces fastener corrosion and produces lighter-weight cured lumber. Copper Azole Type C (CA-C) is the third major formulation, common in southeastern U.S. mills using Southern Yellow Pine substrate.

Weight uplift comes from two sources: (1) the chemical retention itself, typically 0.40-0.80 lb of dry chemical per cubic foot of wood, and (2) the carrier water — usually 100-150% MC immediately after the cylinder cycle. Within 48 hours of treatment, lumber drips most of the surface water but retains the chemical and core moisture. KDAT (kiln-dried after treatment) lumber is re-kilned to ≤19% MC, eliminating most of the water-driven uplift. Reference our untreated lumber calculator for the dry baseline.

Fastener selection follows AWPA M4 and AISI guidelines. ACQ and MCA are more corrosive to galvanized steel than CCA was — most failures come from contractors carrying over CCA-era hardware. The current standard is hot-dipped galvanized ASTM A153 Class D for general use and Type 304/316 stainless for marine and critical structural connections. Mixing aluminum flashing with ACQ-treated lumber causes rapid galvanic corrosion and is prohibited per the 2018 IRC R317.3.