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We want to set the record straight about the changes to the treated wood Use Standards to be published in the American Wood Protection Association’s (AWPA) 2016 Book of Standards. Despite what some companies may be telling you, Above Ground (UC3B) treated wood remains IRC® and IBC® compliant for deck joists, support beams, decking, and railing systems in most deck projects.

There is no requirement to use Ground Contact (UC4A) treated lumber for all structural framing and decking components.

For common deck applications, above ground treated lumber is still one of the best options when used appropriately. Product treated to meet the AWPA standards for above ground use has a history of proven performance while using appropriately less preservative chemical than their ground contact counterpart. This can translate into a more cost-effective option when compared to using material that has all been treated with higher levels of the same preservative chemical for ground contact use.

When it comes to residential decking, here’s what you need to know:

  • The AWPA Use Category System (UCS) continues to allow Above Ground (UC3B) treated wood for applications such as deck joists, support beams, decking, and railings in the most common deck projects.
  • There is NO requirement to use Ground Contact materials for ALL Above Ground decks.
  • Above Ground (UC3B) wood treated to the AWPA standards remains IRC® and IBC® compliant while using the appropriate amount of preservatives required to protect the wood from decay and wood ingesting insects.
  • Wood treated to the AWPA standards is third-party inspected and bears the CheckMark® of Quality on end tags.
  • Viance is not changing its warranty coverage programs on treated wood products, and we will continue to extend the terms of our residential Lifetime Limited Warranty to deck joists, support beams and other decking components that are treated for Above Ground use and used properly.

For more information on why Above Ground (UC3B) treated wood is still the best option for some applications, see our Industry Updates and read all of our Frequently Asked Questions below.

PPP ID# 1531
ICC PP Course #8943
Credit Hours 0.1 Hour

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"Code Compliant Treated Wood for Residential Deck Construction"
Learn more about Code Compliant Wood Preservatives, the AWPA standards and the AWPA's Use Category System (UCS).

If you have additional questions about the revisions to the AWPA-UCS, email us at codequestions@viance.net.

Yes. The AWPA’s standards are directly referenced in the IBC and IRC building codes. The AWPA U1 standard will continue to allow above ground treated wood for use in critical deck joists and support beams, decking, railings, fence pickets, and many other outdoor project applications. Material treated and used for above ground construction with Viance’s preservative treatments will be covered under the terms of our Lifetime Limited Warranty, when used appropriately. This includes material used for above ground deck joists and support beams, which are critical to the performance and safety of an entire structure/project.

New language changes to the AWPA standards and supporting guideline tables can be somewhat confusing. These changes reference the use of (UC4A) retentions on treated wood components considered difficult to replace. Because the difficulty of replacement can be very subjective, standard deck joists and support beams treated to above ground retention levels (UC3B) remain code-compliant.

Products with increased chemical/retention amounts are needed for building components used in high-decay situations (e.g. within 6” of the finished grade and supported on a permeable building materials, in tropical climates, when soil/leaves/debris are left to accumulate/remain and potentially replicate ground contact conditions, poor ventilation around decks, etc.)

Yes. Viance’s residential preservatives are recognized and listed in the AWPA’s Book of Standards, which are referenced in the IBC and IRC building codes. Every preservative standardized by the AWPA is supported by rigorous laboratory and field test data that undergoes an extensive scientific peer review by industry-leading wood scientists, participating academics and independent industry experts/participants. To help ensure that AWPA-standardized products meet ongoing expectations, performance data is scrutinized every five years via the same peer review process to reaffirm its effectiveness.

Some preservatives have undergone a different review process and have received an ICC-ES report. Acceptance of non-AWPA standardized preservatives in construction projects is at the discretion of building code inspectors.

No. Although all deck joists and support beams are critical to a structure, they all will not be required to be treated to ground contact retentions unless at least one of the following conditions occurs:

  • when there is a reasonable expectation that soil, vegetation, leaf litter or other debris may build up and remain in contact with the component
  • when the construction itself, other structures or anticipated vegetation growth will not allow air flow to circulate underneath the construction and between decking boards
  • when components are installed less than six inches above ground (final grade after landscaping) and supported on permeable building materials (e.g. treated wood or concrete)
  • when components are in direct contact with non-durable untreated wood, or any older construction with any evidence of decay
  • when components are wetted on a frequent or reoccurring basis (e.g. on a freshwater floating dock or by a watering system)
  • when components are used in tropical climates
  • deck joists and support beams are deemed difficult to replace

It’s important to select wood that has the appropriate level of preservative for its intended use. The language changes to the AWPA Use Category System and supporting guideline tables are intended to help clarify the scenarios where a higher level of protection should be considered/used. Material that is treated with Viance’s preservatives for Above Ground use are still code compliant (IBC and IRC) and warranted accordingly. For cases where the material may be in higher decay environments/scenarios, a higher level of preservative protection is required.

Lumber that has been treated to AWPA above ground retention levels (UC3B) is standardized to provide a level of performance that is appropriate for above ground applications. Proven above ground products that meet the AWPA standards have historically performed well without the excessive use, or potential costs, associated with increasing those preservative levels for high-decay/ground contact level treatments.

Yes. Because conditions for wood decay are optimal in most soils, material treated for ground contact use is required. Ideal deck building techniques may include the use of non-permeable building hardware (fixed or adjustable), which are used as a barrier between a concrete footer and structural support posts/beams to potentially improve the performance of the treated wood. Measures should be taken to ensure that accumulations of soil/leaves/debris are minimized or prevented during the project planning and construction phase. To extend the performance of the deck materials and components, regular inspection and maintenance should be performed.

No. All treated wood is NOT the same!

Above ground treated lumber is code compliant for use in applications where the wood does not touch the ground (e.g. deck joists and support beams used as critical structural members, decking, railings, and above ground fence pickets), or where a high-decay environment does not exist.

Wood treated to ground contact levels is required for direct contact with the ground (e.g. fence posts, etc.), and in cases where a high-decay hazard is very likely to occur (e.g. soil/leaves/debris build-up or accumulations are left to remain in contact with the wood, poor ventilation, tropical climates, etc.).

Our preservative products Ecolife, Preserve® ACQ® and Preserve® CA are all treated under the AWPA standards for above ground or ground contact retentions to provide proven wood protection.

Ecolife, with its built in wood stabilizing system, has been specifically designed for above ground use, and as such has been proven to perform. Ecolife treated wood exhibits reduced cracking, warping and splitting in service, and uses no more chemicals than is absolutely necessary.

To help ensure you’re getting material that has been treated to the AWPA standards, including being third-party audited, look for the CheckMark of Quality on the end tags of the treated lumber you select. ONLY material that has been treated to these standards is allowed to display this quality CheckMark. Remember, if it doesn’t specifically have the CheckMark of Quality on the tag, you’re not getting material that is treated to the AWPA standards, even if a recognized preservative is used.