Be sure you choose the right fasteners for your project.

It is important to consult the end tag to determine which preservative or preservative system was used in the treatment of that particular product in order to assure the proper fasteners are used.

Choosing Fasteners for Use with ACQ (Alkaline Copper Quaternary) Treated Products

Certain metal products (including fasteners, hardware and flashing) may corrode when in direct contact with products treated with ACQ preservatives.  To prevent premature corrosion and failure it is important to follow the metal products manufacturer’s recommendations.

Approved Fasteners (ACQ):

  • Hot-Dip Galvanized* (The minimum standard) Fastener, hardware, and metal product manufacturers have suggested the minimum Hot-Dip Galvanized requirements for use with treated wood should conform to the following ASTM Standards: ASTM-A153 (for Hot-Dip fastener products) and ASTM-A653 (Coating Designation G-185 for Hot-Dip connector and sheet products). 
  • 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.
  • Other fasteners, hardware or any metal product as recommended by their manufacturer There may be additional products (other than stainless steel or G-185 Hot-Dip Galvanized) which are suitable for use with ACQ treated wood. Please consult with the individual fastener, hardware, or metal product manufacturer for recommendations for use of their products with ACQ treated wood. 
  • Aluminum should not be used in direct contact with wood products treated with ACQ preservatives Spacer materials or other physical barriers are recommended to prevent direct contact of ACQ treated wood with aluminum products. 

Other alternative wood preservative manufacturers’ recommendations include**: 

* Electroplated galvanized fasteners and metal products are typically not accepted by the building codes for use in exterior applications, regardless of the type of wood used.

Download ACQ Fastener Information Sheet:

ACQ Fastener Information Sheet PDF (Includes hardware manufacturers) 


Choosing Fasteners for Use with Micronized Copper Treated Products

Micronized copper treated products offer many benefits including significantly improved corrosion performance. YellaWood® brand pressure treated pine with micronized copper preservatives exhibits corrosion rates on metal products similar to CCA pressure treated wood, and untreated wood.

  • For interior or exterior applications - Use fasteners and hardware that are in compliance with the manufacturer’s recommendations and the building codes for their intended use. As with any good design and construction practices, micronized copper treated wood should not be used in applications where trapped moisture or water can occur.  Where design and/or actual conditions allow for constant, repetitive or long periods of wet conditions, only stainless steel fasteners should be used.
  • For exterior applications - The following galvanization levels may be used for connectors, joist hangers, fasteners and other hardware that are placed in direct contact with exterior applications of micronized copper treated wood:

    Fasteners - nails, screws, etc. ASTM - A 153 (1 oz./ft²)

    Hardware - connectors, joist hangers, etc. ASTM - A 653 G90 (0.90 oz./ft²)

    The effects of other building materials within a given assembly, along with environmental factors, should also be considered when selecting the appropriate hardware and fasteners to use for a given project containing treated wood.

    Stainless Steel fasteners and hardware 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 recommended grades to use.  
  • Aluminum building products may be placed in direct contact with YellaWood® brand products with micronized copper preservatives used for interior uses and above ground exterior applications such as decks, fencing, and landscaping projects. Examples of aluminum products include siding, roofing, gutters, door and window trim, flashing, nails, fasteners and other hardware connectors. However, direct contact of micronized copper treated products and aluminum building products should be limited to code-compliant construction applications that provide proper water drainage and do not allow the wood to be exposed to, or remain in contact with a continual moisture source, standing water or water immersion. In addition, micronized copper treated wood should not be encased, sealed, or wrapped with aluminum products where trapped moisture or water can occur so as to avoid pitting or other unwanted results.  

We recommend you contact the aluminum building products manufacturer for its recommendations regarding use of its aluminum products in contact with micronized copper treated wood in ground contact applications or when exposed to salt water, brackish water, or chlorinated water, such as swimming pools or hot tubs.

Also check with the aluminum building products manufacturer regarding compatibility with other chemicals and cleaning agents. Contact Osmose for further information on aluminum contact use in commercial, industrial, and specialty applications such as boat construction.

Download Micronized Copper Fastener Information Sheet:

Fastener Information Sheet PDF

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