Yes, repainting rusted corrugated iron roofing is a job a capable DIYer can tackle — but the preparation is everything. Rush the prep and your new paint will peel within a season. Do it properly and a good topcoat can protect your roof for 10–15 years or more.
Assess the Roof First
Before you buy a single tin of paint, get up there (safely) and have a thorough look. You're checking for:
- Surface rust — orange staining but the metal is still solid. This is treatable.
- Pitting or deep corrosion — the metal is thinning but still intact. Treatable with care.
- Holes or perforations — the iron has rusted through. Individual sheets may need replacing.
- Loose or missing fasteners — replace these before painting.
- Damaged flashings or ridgecapping — address these at the same time.
If more than a quarter of the sheets are perforated or badly corroded, it may be more cost-effective to re-roof entirely. A qualified roofer can give you an honest assessment — find one on tradedirectory.co.nz.
Safety First — Working at Height
Working on a roof is one of the most common causes of serious injury in New Zealand. WorkSafe NZ requires that fall risks be properly managed, even for homeowners doing their own work.
- Use a roof ladder (one with a ridge hook) to spread your weight and avoid walking directly on the corrugations.
- Set up scaffolding or edge protection if the eave height makes falls a serious risk — this is strongly recommended. Check WorkSafe NZ guidance for specific requirements.
- Never work on a wet, frosty, or windy day.
- Have someone on the ground with you at all times.
- Wear non-slip footwear and a hat with sun protection.
What You'll Need
| Item | Purpose |
|---|---|
| Wire brush / angle grinder with wire wheel | Remove loose rust and flaking paint |
| Pressure washer or stiff scrubbing brush | Clean the surface |
| Rust converter or inhibiting primer | Treat remaining rust |
| Roof primer | Adhesion base coat |
| Roof topcoat paint | UV and weather protection |
| Paint roller (long-nap) or airless sprayer | Application |
| Safety gear (harness, gloves, goggles, P2 mask) | Personal protection |
Step-by-Step: Cleaning and Repainting
1. Clean the Roof Thoroughly
Start by removing all loose debris, moss, and lichen. A pressure washer works well — use a fan nozzle and work down the slope. For moss and lichen, a diluted bleach solution or a purpose-made roof wash product can help. Allow the roof to dry completely (at least 24–48 hours in fine weather) before proceeding.
2. Remove Loose Rust and Old Paint
Use a wire brush or angle grinder with a wire cup wheel to remove all flaking paint and loose rust. This is the most labour-intensive part of the job — don't cut corners. Wear a P2 dust mask, safety glasses, and gloves. Old paint on pre-1980s roofs may contain lead; if in doubt, have it tested before sanding or grinding.
3. Apply Rust Converter or Inhibiting Primer
For any remaining rust that's bonded to the metal, apply a rust converter (which chemically neutralises rust) or a rust-inhibiting primer. Products from Resene and Dulux both offer suitable primers for metal roofing — check their technical data sheets for the correct product for your situation. Allow to cure as per the manufacturer's instructions.
4. Apply a Full Primer Coat
Once rust treatment is done, apply a metal roof primer over the entire surface. This ensures good adhesion for your topcoat. Pay extra attention to overlaps, ridges, and any repaired areas.
5. Apply the Topcoat
Choose a roof paint specifically formulated for corrugated iron — not a general exterior paint. Quality roof paints from Resene, Dulux, or Wattyl are widely available in NZ and come in a range of colours. Apply at least two topcoats, allowing full drying time between coats. A long-nap roller works well for corrugated profiles; an airless sprayer is faster but requires more masking and skill.
6. Check Flashings and Fasteners
Once painting is complete, inspect all flashings, ridgecapping, and roofing screws. Replace any corroded fasteners with hex-head roofing screws with neoprene washers. Seal around penetrations (pipes, skylights) with a compatible roofing sealant such as those available from Sika.
Does This Need a Building Consent?
In most cases, repainting an existing roof does not require a building consent — it's maintenance, not alteration. However, if you're replacing sheets or making structural changes, check with your local council. MBIE Building Performance has guidance on Schedule 1 exemptions, but always confirm with your council before starting work.
When to Call a Professional
Consider hiring a qualified roofer if:
- The roof pitch is steep (generally over 25°) or the height makes safe access difficult.
- You find widespread perforation, structural damage, or rotten purlins underneath.
- You're unsure about lead paint — a professional can test and manage this safely.
- You want a warranty-backed job, particularly on a rental property subject to the Healthy Homes standards.
- You simply don't have the time, equipment, or confidence to do it safely.
A professional roofer will have the right equipment, experience, and insurance. You can find qualified local roofers on tradedirectory.co.nz.
Roofing Association of NZ (RANZ)
Licensed Building Practitioner (LBP)
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