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Changes in Pressure-Treated Lumber
According to tests designed and approved by the American Wood-Presevers’ Association, the new new treated lumber is more corrosive to fasteners than the old CCA (Chromated Copper Arsenate) treated wood. The manufacturers of ACQ (Alkaline Copper Quat), CA (Copper Azole Type A and B) and SBX (Sodium Borate) and the treated wood industry are all recommending hot-dipped galvanized and stainless steel nails and screws with their treated wood products.  Fasteners must meet the ASTM A-153 specification for hot-dipped gavanizing.

Fastener Recommendations
When selecting deck fasteners, framing nails, decking nails or screws, take note of the holding capacity and the resistance to corrosion.  When quoting an outdoor construction project for a client, encourage them not to skimp on the fasteners.  Using the wrong fasteners can compromise the appearance, longevity, and safety of their project.

Many fasteners traditionally used with treated lumber are no longer recommended for this application.  Dacrotized, electroplated, brass, and aluminum fasteners should not be used in treated lumber when the visible appearance of rust or the likelihood of corrosion is unacceptable.

Acceptable Fasteners for Pressure-Treated Lumber

GOOD - Non-metallic finish:
Includes but is not limited to triple coated screws first galvanized then covered with a ceramic or Teflon (or similar material) layer with a top sealer coat.

BETTER - Hot-Dip Galvanized:
The requirements for use with treated wood should conform to the following ASTM Standards: ASTM-153 (for Hot-Dip fastener products) and ASTM-A 653 (Coating Designation G-185 for Hot Dip connector and sheet products).  NOTE:  Hot Galvanized does not equal Hot Dip Galvanized.

BEST - Stainless Steel:
Stainless steel fasteners and connectors are required for Permanent Wood Foundations below grade and are recommended for use with treated wood in other severe exterior applications such as swimming pools, salt water exposure, etc.  Type 304 and 316 are the recommended grades to use.

Manufacturer Recommended Fasteners and Hardware:
There may be additional products (other than stainless steel or hot-dip galvanized) which are suitable for use with ACQ treated wood.  Please consult with the fastener or hardware manufacturer for use recommendations.

Pressure-Treated Lumber

ACQ .25 treated wood is approved for exterior use above ground
ACQ .40 treated wood is approved for exterior use and can be touching or in the ground or in fresh water
ACQ .60 is treated wood approved for use in permanent wood foundations, while wood treated to 2.5 is for use in piers or pylons in salt water

Fairfield Hardware is not liable for errors or omissions. Always check you local building codes.