Corrosion Protection for Metal Connectors in New Zealand: An Engineer’s Perspective
August 11, 2025
New Zealand’s varied environmental conditions—including extensive coastal exposure, high rainfall regions, and geothermal zones—require a strategic approach to corrosion protection for metal connectors. Designers must consider environmental exposure, material compatibility, and compliance with the New Zealand Building Code (NZBC) to ensure structural integrity and long-term durability.
NZS 3604 is New Zealand’s Acceptable Solution and the most commonly referred to Standard for the design and construction of timber-framed buildings. It provides a means of compliance with the NZBC and includes detailed requirements for durability, fixings, and corrosion protection.
Corrosion Protection Requirements are covered in Section 4 of NZS3604 and include exposure zone maps, environment and exposure definitions, and specific requirements for corrosion protection on metal fasteners and connectors for the different environments.
Metal Fasteners and Connectors must be protected against corrosion appropriate to the exposure zone (e.g., sea spray, geothermal, or urban). Stainless steel or non-corrosive material is required in sea spray zones or where timber is treated with corrosive preservatives (e.g., CCA, ACQ).
Exposure Zones from BRANZ:
Simpson Strong-Tie provides corrosion guidance tailored to New Zealand conditions:
| Environment | Recommended Material/Coating |
|---|---|
| Low - Dry Internal | Z275, Zinc-plated or mechanically galvanized steel |
| Medium - Sheltered Zones B & C | ZMAX, Hot-dip galvanized (HDG) or Double-Barrier coating |
| Severe | 304/316 stainless steel |
| Marine/Coastal | Proprietary severe-duty coatings |
| All External and Sheltered Zone D | FREP material |
Key Notes:
Fastener Compatibility: Always match fastener material to connector material to avoid galvanic corrosion.
- Where products are used in applications that do not require the typical 50 year working life, it may be feasible to meet the requirements of the NZBC using lower corrosion protection for a lesser specified working life.
- Applying protective coating like primers and sealant may also provide additional durability.
- Preservative-Treated Timber: Use corrosion-resistant fasteners (e.g., stainless steel) with ACQ, CCA, or other aggressive treatments.
- Consideration must be given to microclimates that include industrial contamination and corrosive environments, agricultural chemicals or fertilizers and geothermal hot spots, which should be assessed by corrosion experts.
Corrosion protection in New Zealand is not one-size-fits-all. Engineers and Designers must align their material and coating choices with the NZBC, NZS3604 and Simpson Strong-Tie’s guidance. By understanding the environmental exposure and applying the right protection strategy, longevity and structural safety of metal connectors can be ensured across New Zealand’s diverse climates.
Structural Connections
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With nearly 60 years of field and R&D experience, Simpson Strong-Tie® timber connectors are manufactured to the industry's highest standards. From framing angles to straps to heavy-duty joist hangers, we offer the most diverse product line so that you have the right product for the job.
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