Structural connections: the weakest links in the load path

A building only stands up if every load has a continuous path to the ground: roof → rafters → walls → floor → piles → footings. Connections are the links in that chain, and a chain is only as strong as its weakest link. They’re rated in kN (kilonewtons) and must be chosen for both the load they carry and the corrosion environment they live in.

The load path — why connections matter

In a storm, wind tries to peel the roof off and push walls over; in a quake, the ground throws the whole house sideways. The framing members are strong — it’s the joints between them that fail. NZS 3604 (and proprietary systems like Pryda and MiTek) give tested connectors so the path holds together:

• Hangers carry gravity.
• Straps and ties resist uplift.
• Anchors and hold-downs tie it all to the foundation.

The connector families

Joist hanger — Pryda KingPin / MiTek JH series

• Spec: Galvanised (Zone A/B), SS316 (Zone C/D). Sized to joist depth — 140, 190 and 240 sizes are common.
• Use: Where joists frame into the side of a bearer or beam instead of sitting on top — e.g. a continuous joist line at a deck-to-house junction.
• Note: Nails are 30×3.15 H-spec or proprietary hanger nails. See NZS 3604 §7.1.5.5.

Strap tie — Pryda CS500 (10 kN), CS400 (8 kN), CS300 (6 kN)

• Spec: Galvanised steel strap, 30×1.0mm typical, nailed each end.
• Use: Top plate to rafter uplift (NZS 3604:2011 Table 10.13), continuity over multi-storey, and tying a header to king studs.
• Note: Strap centres vary by wind zone — read the required centres off NZS 3604:2011 Table 10.13 for your wind zone.

Nail plate / gang nail — MiTek M20, Pryda Gang Nail

• Spec: Truss and lintel connection plates with pre-pressed teeth.
• Use: Truss heel joints and lintel-to-trimmer continuous splices.
• Note: Truss-only — never field-installed without an engineer.

Hold-down anchor — Simpson Strong-Tie HD2A, Pryda HD500

• Spec: Bolted hold-down for a bracing wall to the floor — typically 1×, 2× or 3× M16 bolts.
• Use: GIB EzyBrace systems that require hold-downs (GS1-N, GS2-N, BL1-H etc.) — bolts the wall bottom-plate corner to slab or to lower-storey timber.
• Note: Often misunderstood — GS2-NOM (no hold-down) gives 50 BU/m without; the hold-down adds capacity.

Coach screw (lag bolt) — various (Senco, Buildex)

• Spec: M8/M10/M12 hex-head wood screw, 75mm–200mm long, galvanised or SS316.
• Use: Bolting timber to timber where through-bolting is impractical — stringer-to-house, bearer-to-pile.
• Note: Pre-drill a pilot hole 80% of the shank diameter to avoid splitting. See NZS 3604 §7.5.12 for capacities.

Hex bolt (through-bolt) — M8/M10/M12 hot-dip galv or SS

• Spec: Fitted with a nut and washers each end. A 50×50×3mm square washer is the NZ standard.
• Use: Bolting timber connections through the member.

Two things every connector choice comes down to

Whichever family you reach for, pin down two things before you fix anything:

1. Load: match the kN rating to the force the joint carries — gravity through hangers, uplift through straps and ties, and the tie-down to the foundation through anchors and hold-downs.
2. Corrosion environment: galvanised holds up in milder zones, while SS316 is the pick for the harsher coastal zones (Zone C/D on the hangers above).