A fresh coat of paint can add years to your roof's life and dramatically improve your home's kerb appeal — but only if the surface is properly prepared first. Skipping or rushing the prep work is the number-one reason roof paint fails prematurely in New Zealand's variable climate. Follow these steps to give your roof coating the best possible foundation.
Assess Your Roof's Condition First
Before you pick up a brush or pressure washer, do a thorough inspection from the ground using binoculars, then carefully from a ladder at the eaves. Look for:
- Cracked, broken, or slipped tiles (concrete or clay)
- Rusted or lifted screws and flashings on metal roofs
- Moss, lichen, and algae growth — extremely common in NZ's humid regions
- Delaminating or chalky existing paint that will need to be removed
- Sagging or soft areas that could indicate structural issues underneath
If you spot significant structural damage, consult a Licensed Building Practitioner before proceeding. Painting over a structurally compromised roof is a waste of time and money.
Safety First — Working at Height
Roof work is one of the leading causes of serious injury in New Zealand. WorkSafe NZ requires that any work at height be carried out with appropriate fall protection. For homeowners, this means:
- Using a roof ladder (one that hooks over the ridge) rather than walking directly on tiles
- Setting up scaffolding or edge protection for anything beyond a single-storey lean-to
- Never working alone, and never on a wet or windy day
- Wearing non-slip footwear and a safety harness where practical
If you're not confident working at height, this is a job best left to a professional roof painter — you can find qualified local tradespeople on tradedirectory.co.nz.
Step 1 — Kill Moss, Lichen, and Algae
New Zealand's damp climate means biological growth is almost guaranteed on older roofs. This must be treated before pressure washing, not after.
Apply a dedicated moss and mould killer or roof treatment product (available from Mitre 10 or Bunnings) and allow it to dwell for the time specified on the label — often 24–48 hours. This kills the organisms at the root so they wash away cleanly rather than being spread around by the pressure washer.
Step 2 — Pressure Wash Thoroughly
Once the biological treatment has done its work, pressure wash the entire roof surface. Key tips:
- Use a medium-pressure setting (around 1,500–2,000 PSI as a guide) — too high can damage concrete tiles or strip granules from aged surfaces
- Work from the ridge down to the gutters so dirty water runs off naturally
- Pay extra attention to valleys, gutters, and any areas with heavy moss build-up
- Allow the roof to dry completely — typically at least 24–48 hours of fine weather — before moving to the next step
A wet surface will cause paint to blister and peel, so patience here pays dividends.
Step 3 — Make All Repairs
With the roof clean and dry, go back and fix everything you identified in your initial assessment:
- Replace cracked or broken tiles — concrete tiles are widely available from roofing suppliers
- Re-bed and re-point ridge and hip cappings using a flexible pointing compound
- Treat rust spots on metal roofs with a rust converter product before priming
- Re-seal or replace flashings around chimneys, skylights, and penetrations using an appropriate sealant such as those in the Sika range
- Replace any lifted or missing screws on corrugated iron or steel roofs with new self-tapping screws and neoprene washers
Do not skip this step. Paint is not a waterproofing solution — it will not seal a cracked tile or a leaking flashing.
Step 4 — Apply Primer
Primer is essential for adhesion, especially on:
- Bare concrete or terracotta tiles that have never been painted
- Repaired or patched areas
- Bare metal exposed after rust treatment
- Highly porous or chalky surfaces
Choose a primer that is compatible with your chosen topcoat. Resene and Dulux both offer roof-specific primer systems with technical data sheets that specify correct application rates and recoat times. Always follow the manufacturer's instructions.
Choosing the Right Paint System
Not all paints are suitable for roofs. Use a product specifically formulated for roof surfaces — these are designed to handle UV exposure, thermal movement, and New Zealand's freeze-thaw cycles in colder regions.
| Roof Type | Recommended Coating Type |
|---|---|
| Concrete tiles | Acrylic roof membrane or tile paint |
| Terracotta/clay tiles | Breathable acrylic roof paint |
| Corrugated steel/iron | Metal roof paint with rust inhibitor |
| Colorsteel® (pre-painted steel) | Compatible acrylic topcoat |
Check with your paint supplier — Wattyl also has a range of roof coatings suited to NZ conditions.
When to Call a Professional
While a competent DIYer can handle preparation and painting on a simple, low-pitched roof, there are situations where you should engage a qualified roof painter or other tradesperson:
- Steep or high roofs where fall risk is significant
- Structural repairs to the roof framing (restricted building work under the NZ Building Code — requires an LBP)
- Plumbing or drainage work around roof penetrations (restricted work under the Plumbers, Gasfitters and Drainlayers Board)
- Any electrical work near roof-mounted equipment (restricted work under the EWRB)
- Large or complex roofs where professional equipment and experience will deliver a far better result
A professional roof painter will also be able to advise on the best coating system for your specific roof type and local climate conditions. Find a trusted local roof painter at tradedirectory.co.nz.