Re-roofing checklist

Measure twice

Work out your roof area plus laps and overhangs, then add ~10% for offcuts. Note the pitch - low pitches need longer-run, higher-rib profiles to shed water.

List every penetration (vents, flues, skylights) so you order the right flashings and boots up front.

Choose your profile

Corrugate and trapezoidal (trapezoidal/IBR-style) are the common NZ options. Match new sheets to existing where you're patching.

Coastal or alpine? Step up to a heavier coating (e.g. AZ150 / Colorsteel-equivalent) for corrosion resistance.

Underlay, flashings and fixings

Run a self-supporting roofing underlay/sarking to manage condensation. Order ridge, barge, apron and valley flashings to suit your layout.

Use the right fasteners: Class 4 (or stainless near the coast) self-drilling roofing screws with EPDM washers, sized for your purlin material.

Stay compliant

Roofing is a BPIR designated product - keep the supplied product information statements with your build records.