A small hole in your corrugated iron roof — whether from a popped fastener, rust, or accidental damage — can usually be patched as a DIY repair if you're comfortable working at height and the damage is genuinely minor. Act quickly, because even a pinhole can let in enough water to cause significant damage to your ceiling, insulation, and framing over a wet NZ winter.
Assess the Damage First
Before climbing up, inspect the roof from inside your ceiling space after rain to locate exactly where water is entering. From outside, look for:
- Rust-through holes — often surrounded by discolouration or flaking paint
- Holes from lifted or missing screws/nails — the fastener may have corroded or worked loose
- Impact damage — small punctures from falling branches or hail
If the hole is larger than roughly 50 mm across, or if you notice widespread rust, sagging sheets, or multiple problem areas, a patch is likely only a temporary fix. In that case, replacement of the affected sheets — or the whole roof — is worth considering.
Safety First — Working at Height
Roof work carries real risk. Before you go up:
- Never work on a wet or frosty roof — corrugated iron is extremely slippery
- Use a roof ladder (one that hooks over the ridge) to spread your weight and avoid walking directly on the sheets
- Always have someone on the ground with you
- Check WorkSafe NZ guidelines on working at height before starting
- If your roof pitch is steep (generally over 25°) or you're not confident, call a professional roofer
Tools and Materials You'll Need
- Wire brush or angle grinder with flap disc
- Clean rags and solvent (e.g. methylated spirits)
- Roofing sealant — a polyurethane or butyl-based product suitable for metal roofs (available at Bunnings or Mitre 10)
- Metal repair patch — purpose-made aluminium or galvanised steel flashing tape, or a cut piece of matching corrugated iron
- Pop rivets and rivet gun (if using a metal patch)
- Roofing screws with neoprene washers
- Roof paint to finish (match your existing colour if possible)
Step-by-Step: Patching a Small Hole
1. Clean and Prepare the Area
Use a wire brush to remove all loose rust, dirt, and flaking paint around the hole — at least 50–75 mm in every direction. Wipe down with methylated spirits and allow to dry completely. Good surface prep is the most important step; sealant and patches won't bond properly to a dirty or rusty surface.
2. Apply Roofing Sealant for Pinhole Repairs
For very small holes (under about 5 mm), a high-quality polyurethane roofing sealant applied with a caulking gun may be sufficient on its own. Work the sealant firmly into the hole and feather it out 30–40 mm around the edges. Smooth with a wet finger or spatula. Allow to cure fully before rain — check the product's data sheet for cure times.
Sika offers roofing sealant products suitable for metal roofs — always read the product data sheet to confirm compatibility with your roof material and any existing coatings.
3. Apply a Metal Patch for Larger Holes
For holes up to around 50 mm, cut a patch from a piece of matching corrugated iron or flat galvanised sheet, making it at least 100 mm larger than the hole in every direction. Alternatively, use a purpose-made aluminium flashing tape for a quicker fix.
- Apply a bead of roofing sealant around the perimeter of the hole
- Press the patch firmly into place, following the corrugation profile as closely as possible
- Secure with pop rivets or roofing screws around the edges, sealing each fastener head with sealant
- Apply another bead of sealant around all patch edges and smooth off
4. Prime and Paint
Once the sealant has cured, apply a metal primer followed by a topcoat in a matching colour. Resene and Wattyl both stock roofing paints suitable for corrugated iron — ask in-store for a product compatible with your roof type (Zincalume, galvanised, or painted steel).
Does This Need a Building Consent?
Minor repairs like patching a small hole are generally exempt from building consent under Schedule 1 of the Building Act — but always confirm with your local council before starting, especially if the repair involves replacing a significant area of roofing. MBIE Building Performance has useful guidance on what work requires consent.
When to Call a Professional
Contact a qualified roofer if:
- The hole is larger than 50 mm, or there are multiple holes
- You notice widespread rust, soft spots, or the iron feels thin and fragile
- The roof pitch or height makes safe access difficult
- Water damage has spread to the roof structure, insulation, or ceiling lining
- You're a landlord — Tenancy Services Healthy Homes standards require rental properties to have a roof in good condition
A qualified local roofer can assess whether a patch will hold long-term or whether sheet replacement is the smarter investment. You can find experienced roofers in your area on tradedirectory.co.nz.