Hobson technical document
Corrosion Resistance of Metal Connectors: Choosing Galvanised or Stainless by Zone
A four-page Hobson technical guide to picking the right finish for metal connectors in timber framing, such as strapping, joist hangers, framing brackets and truss plates. It works in three steps: find the corrosion zone, decide whether the connector is enclosed, sheltered or exposed, then read off the minimum corrosion protection.
What this covers
- How corrosion happens
- Minimum protection by zone
- AS 4312 corrosivity zones
- Exposure conditions
Applies to Bracing Strap, Joist Hangers and Triple Grip-Style Connector.
Key things to remember
The essentials from this document in plain words. Check the full document before you rely on a figure.
- Most metal connectors are expected to last the life of the building, typically 50 years for normal buildings, so the finish has to suit the environment.
- Enclosed (inside the building envelope): Z275 galvanised in seaspray, industrial and coastal zones, and zinc plated in very low and low hazard zones (C1/C2).
- Exposed to weather and rain, such as decks, pergolas and open sub-floors: stainless steel 304 or 316, or hot dip galvanising. In seaspray zones (C4/C5/CX) it must be 304 or 316 stainless.
- Sheltered from rain but open to wind-blown salt, such as open balconies and garages: Z275 galvanised with a soft seal coating, or 304/316 stainless, in coastal and industrial zones; stainless only in seaspray zones; Z275 in low hazard zones.
- Within 2m of a pool edge, every connector should be 316 stainless, enclosed or not.
- Corrosivity examples from the AS 4312 table: C2 covers most of Australia 50km from the coast; C4 is from the shoreline to 50m inland around sheltered bays; CX is surf beach shorelines with very high salt deposition.
Who it helps: Builders and designers specifying joist hangers, straps and brackets near the coast, pools or industry.
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