In a genuine emergency — a leaking roof before a storm hits — it's tempting to grab whatever paint is on hand. However, using standard exterior house paint on a roof is not recommended and will almost certainly fail within months, potentially making the underlying problem worse. Here's what you need to know before you climb that ladder.
Why Exterior House Paint Isn't Suitable for Roofs
Exterior wall paints are formulated for vertical or near-vertical surfaces that shed water quickly and aren't subject to constant UV bombardment, foot traffic, or the extreme thermal cycling that a roof endures. A NZ roof can swing from near-freezing overnight to 60–70 °C on a hot summer's day on the surface itself. Standard exterior paints:
- Lack the flexibility to expand and contract with metal or concrete tiles through these temperature swings, leading to cracking and peeling.
- Are not waterproof membranes — they are moisture-resistant at best, and on a low-pitch or flat roof, standing water will penetrate them rapidly.
- Have insufficient UV stabilisers for the intense UV radiation NZ receives, causing premature chalking and breakdown.
- Won't bond correctly to roofing substrates such as Colorsteel, concrete tiles, or butynol without the correct primer system.
Using the wrong product can also void any remaining warranty on your roofing material and may create adhesion problems for the professional coating that will eventually need to go over the top.
What to Use in a Genuine Emergency
If you have an active leak and need a short-term fix right now, there are better options than exterior house paint:
Roofing Repair Tapes and Sealants
Butyl rubber tape or flashing tape (available at Bunnings or Mitre 10) can be pressed over cracked flashings, small holes, or open laps as a temporary measure. Products from Sika such as polyurethane sealants are also widely used by tradespeople for emergency sealing around penetrations.
Emergency Roof Coatings
If you need to apply something over a larger area, look specifically for a roof membrane or roof coating product rather than wall paint. Products labelled as roof coatings are formulated with the elasticity and waterproofing properties a roof demands. Ask at your local trade store for a product suited to your specific roof type (metal, concrete tile, or membrane).
Tarpaulins
For a very short-term fix — say, overnight before a tradesperson arrives — a heavy-duty tarp secured over the affected area is often the safest and most effective emergency measure. It won't cause any damage to the roof surface and is easy to remove.
Safety First: Working on a Roof
Before you do anything on a roof, please consider your safety seriously. Falls from roofs are one of the leading causes of serious injury and death in NZ. WorkSafe NZ requires that anyone working at height takes appropriate precautions. For homeowners doing minor DIY:
- Never work on a wet, frosty, or windy roof.
- Use a properly footed ladder that extends at least 1 metre above the roof edge.
- Consider hiring or borrowing roof anchor points and a harness for anything beyond the very edge.
- Have someone present who knows where you are.
If the pitch is steep, the roof is high, or you're not confident, stop and call a professional.
NZ Building Code Considerations
Roofing work in NZ must comply with the NZ Building Code, particularly Clause E2 (External Moisture), which requires roofs to prevent moisture from entering the building. A temporary patch using the wrong materials doesn't relieve you of this obligation long-term. If your roof has significant damage, a building consent may be required for repairs — check with your local council, as requirements vary. Minor maintenance and like-for-like repairs often fall under Schedule 1 exemptions, but confirm this before proceeding.
What a Proper Roof Paint Job Involves
When the emergency has passed, a proper roof repaint by a qualified roof painter will typically include:
| Step | Purpose |
|---|---|
| High-pressure wash | Remove moss, lichen, dirt, and chalking |
| Moss and mould treatment | Kill biological growth and inhibit regrowth |
| Spot priming | Seal bare metal, rust spots, or repaired areas |
| Full primer coat | Ensure adhesion of the topcoat system |
| One or two topcoats | Provide UV protection, waterproofing, and colour |
Products from Resene, Dulux, and Wattyl all offer dedicated roof coating systems with specific primers for metal and concrete tile roofs. Always follow the manufacturer's data sheet for your specific substrate.
When to Call a Professional
Call a qualified roof painter or roofing contractor if:
- The leak is significant or the damaged area is large.
- Your roof is steep, high, or difficult to access safely.
- You're unsure what your roof is made of or what products are compatible.
- The damage may involve structural elements (battens, sarking, or underlays).
- You want the work to carry any warranty or be compliant with the NZ Building Code.
A professional roof painter will have the right equipment, access to trade-grade products, and the experience to identify underlying issues you might miss. You can find qualified local roof painters on tradedirectory.co.nz.
Master Painters NZ member
Licensed Building Practitioner (LBP)
Roofing Association of NZ (RANZ)
