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Use Stainless Steel Fasteners With Treated Timber!

Last Updated: 30/10/20 at 8:45am

Author: Jamie Hunt

A question often asked of us at Anzor is: are Stainless Fasteners OK with treated timber?

Well the research says not only is it OK – but it is preferred! The Ministry of Business, Innovation and Employment (aka Building & Housing) in conjunction with independent research body BRANZ have conducted significant testing to find out what would be the most suitable metal fasteners to use with various timber treatments.

The BRANZ report on which fastener material to use in treated timber is very clear:


“BRANZ is currently recommending that for both 15- and 50-year situations where CuAz- and ACQ-treated timbers are used, the fastener material of choice, including nails and screws, should be either: 304/316 grades of stainless steel, or durable equivalents, such as silicon bronze”


With the NZ Ministry of Business, Innovation and Employment (Building & Housing) going even further:


“In the past there have been timber fastener durability concerns with the use of new high copper treatment options as an alternative to the traditionally used CCA treatment (refer to Build magazine February/March 2007). In that article it was recommended to use stainless steel fasteners or durable equivalents such as silicon bronze, when using these new treatments in timber exposed to the weather.

This led to the Department co-sponsoring further research. BRANZ is now publishing details of this three-year study confirming that significant corrosion rates are being experienced by both mild steel and galvanised nails and screws used as fasteners in Copper Azole (CuAz) or alkaline copper quaternary (ACQ) treated timber (refer to Build article August/September 2009).

We recommend the use of 304/316 grades of stainless steel or durable equivalents such as silicon bronze for all timber fasteners, including nail plates, bolts and nails, for all CuAz or ACQ treated timber exposed to the weather.  The research confirms the corrosion concerns that initiated the study. The Department’s recommendation endorses that made by BRANZ in the Build February/March 2007 edition and confirmed in the recent Build publication.”


For a full range of Stainless Construction Fasteners see Anzor – for Stainless Nails,  Stainless BoltsStainless Screws, Stainless Lumberlok and Bowmac, or call, email or come visit us to help.

NB: This information is provided as a guide only and Anzor does not accept liability for the application of this information. For advice about stainless steel contact the Nickel Institute.

About Jamie Hunt

Jamie Hunt is the CEO of Anzor Fasteners Ltd, with 24 years for procurement and supply of Stainless Steel Fasteners and Hardware under his belt. He also has Olympic yachting experience and is a Certified ISSF Stainless Specialist.

Jamie is a member of the New Zealand Stainless Steel Development Association and has written many articles including "The Stainless Steel Guide", "Can you paint stainless steel?" and "Are stainless fasteners OK with treated timber?". Check out Jamie on his LinkedIn profile for more information.

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