Pressure-Treated Wood for Post-Frame Construction

Pressure-Treated Wood for Post-Frame Construction

Properly treated wood lasts when in contact with soil, making post-frame construction a quality construction option for long-term, permanent building use.

For post-frame construction, pressure-treated wood is primarily used for skirtboards and building posts or laminated columns. Plywood sheathing, girts and other framing members may also be treated in areas prone to aggressive attack by termites or if increased fire resistance is desired.

The most popular preservatives now in use for post-frame construction are chromated copper arsenate (CCA), alkaline copper quaternary (ACQ), micronized copper quaternary (MCQ), copper azole (CA), and several less widely used treatments.

Specifying by Use

The American Wood Protection’ Association, which establishes the standards for preservatives and treated wood, now organizes standards by a Use Category system.

Applications for post-frame building use are highlighted in the brochure "Pressure-Treated Wood for Post-Frame Construction." You may print this brochure and distribute it to anyone you wish.

Order Free Brochures

Lumberyards are encouraged to keep copies of this brochure on-hand to distribute to builders and other customers who intend to erect post-frame structures, such as pole barns or pole buildings.

CCA - Allowed Usage in Post-Frame Building Construction

CCA-treated wood is still allowed in most types of post-frame construction in accordance with 2002 AWPA Treated Wood Commodity Standards, which may only be applied to CCA. Generally, CCA-Treated wood may be used in post-frame buildings for plywood and wood shingles* (C9), agricultural buildings (solid sawn posts and commodity lumber less than 5” on any side if installed vertically** - C16), in any dimension for marine environments (C18) and in residential and commercial buildings for solid-sawn posts larger than 5" on all sides (C24) and for laminated columns (C28).

* CCA-treated plywood and shingles are not prohibited, but they are not recommended for use on playground equipment. Plywood is permissible at all retentions per AWPA C9 (Plywood). CCA is not allowed for any roof-related applications (such as roof trusses) unless members are larger than 5x5” - with the exception of wood shingles.

** Arch Wood Protection interprets standard C16 (Wood Used on Farms) to include structural members in any dimension, provided they are installed vertically in strictly agricultural applications. Osmose and Viance interpret the standard to disallow any members less than 5” on any one side. Be sure to comply with the interpretation of the manufacturer of the chemical your wood treater uses.