Wind uplift fixings: tying the roof down

Wind uplift fixings are the connectors that tie your rafters and trusses down to the top plate so the roof doesn’t lift in a blow. The higher the wind zone, the closer together and higher-capacity those fixings need to be — get it wrong and it shows up at pre-line inspection.

Reading the requirement off Table 10.13

The required fixing centres and the uplift capacity (in kN/m) by wind zone are tabulated in NZS 3604:2011 Table 10.13. We don’t reproduce those rows — read them off your licensed copy of the standard for your wind zone. Extra High wind zones may require specific engineering.

Picking a connector that meets the number

Once you know the required capacity from the table, pick connectors with published kN ratings that meet or exceed it:

• Toenails (multiple 100×3.75) — the lowest-capacity option, for light roof and lower wind zones only.
• Pryda CS300 / CS400 / CS500 strap (and equivalent MiTek straps) — these carry published kN ratings (for example, CS500 ≈ 10 kN). Choose one that meets or exceeds the required capacity from the table.
• Higher wind zones typically need a strap on both faces of the rafter heel, sometimes with supplementary toenails.

What this looks like on site

In high and extra-high wind zones the fixings come close together and often need a strap on both faces of each rafter or truss heel. The straps are cheap (~$2–3 each) but easy to miss at framing time — a pre-line inspection will catch a shortfall. If you’re caught short, fix it by drilling extras and nailing through both faces.

Other uplift fixings in the load path

The rafter-to-plate connection isn’t the only tie-down that matters — the load path runs all the way to the ground:

• Bottom plate to slab — see the “Connections” topic.
• Top of foundation wall to floor — typically a proprietary hold-down (for example, a Pryda HD-series) spaced per the engineer’s PS1.