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Wood preservatives are accepted for building code compliance either by reference to American Wood Protection
Association (AWPA – formerly the American Wood-Preservers’ Association) standards or through the product evaluation
process of the International Code Council (ICC) Evaluation Service. Acceptance of a preservative into the AWPA Book of
Standards, or by ICC evaluation, ensures that properly treated wood products perform satisfactorily for their intended
service condition.
AWPA is the principal standards-writing body for wood preservation in the United States. The AWPA Book of Standards
provides guidance on preservatives, wood use and exposure conditions, treatment process, testing, quality control
and inspection. Manufacturers submit product data to AWPA for peer review and acceptance in the Standard.
Manufacturers may also submit data to the ICC for review, and receive an ICC Evaluation Service Report (ESR) for
code approval. Quality marked pressure-treated wood must reference the ESR report number and identify the code approved
inspection agency.
Building Code Requirements
Pressure-treated Southern Pine is recognized by building codes and regulatory agencies for use in construction.
Specific code requirements for pressure-treated wood are detailed in your local building code. Generally, building
codes require preservative-treated or naturally durable wood for protection in the following
applications:
- Wood in contact with the ground or fresh water
- Wood used above ground in contact with concrete or masonry. Example: Sill plates on a concrete slab
- Wood used above ground where specified distances from exposed earth are not met. Example: Floor assembly when wood joists are closer than 18 inches to exposed earth, or
wood girders closer than 12 inches
- Wood providing structural support and exposed to the weather. Example: Balcony joists without adequate protection to prevent moisture or water
accumulation on the surface or at joints between members
- Wood floor framing in areas where hazard of termite damage is known to be very heavy, unless provided with approved methods of termite protection.
- Wood used below the Design Flood Elevation (DFE)
When used in locations where drying in service cannot readily occur, codes require that pressure-treated wood have a moisture content of 19 percent or less before covering or enclosure. Wood end-cut, notched, or bored at the jobsite must be treated in accordance with American Wood Protection Association Standard M4. Application of copper naphthenate solution having a minimum 2% metallic solution is specified.
Specifying Southern Pine "Dried" After Treatment
Wood products treated with waterborne preservatives
have very high moisture content after removal from the
treatment cylinder. If treated dimension lumber is used
for a framing application where it will be covered or
enclosed, building codes require a moisture content of
19% or less (see Building Code Requirements).
Therefore, any specification for treated framing should
include moisture content requirements after treatment.
Re-dried Southern Pine should bear a mark indicating it
has been air dried (ADAT or Dry) or kiln dried after treatment
(KDAT).
Where drying after treatment is specified for sheathing
and composites, AWPA requires that moisture content not
exceed 19% for each piece, or that allowed by national
grading rules. APA — The Engineered Wood Association
recommends that plywood not exceed 18% moisture content
after drying. For details, visit www.apawood.org.
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