Mould in the bathroom is one of the most common headaches for New Zealand homeowners, especially in older homes or regions with high humidity like Auckland, Wellington, and the West Coast. The good news is that choosing the right paint — and preparing your surfaces properly — can make a significant difference in keeping mould at bay.
Why Bathrooms Are So Prone to Mould
Bathrooms generate a lot of steam and moisture every day. When that moisture condenses on walls and ceilings, it creates the perfect environment for mould spores to take hold. Poor ventilation, cold surfaces, and untreated or low-quality paint all make the problem worse. In New Zealand, the Healthy Homes standards require rental properties to have adequate ventilation, but even owner-occupied homes benefit from good airflow and the right surface coatings.
What Makes a Paint Mould-Resistant?
Mould-resistant paints (sometimes called anti-mould or mould-inhibiting paints) contain fungicidal additives that discourage mould and mildew growth on the painted surface. They are typically formulated with:
- A low-sheen or semi-gloss finish that resists moisture absorption
- Fungicide or biocide additives that inhibit spore growth
- High-quality acrylic or water-based binders that are less porous than older oil-based formulas
It's important to understand that no paint is completely mould-proof — paint is a surface treatment, not a substitute for fixing the underlying moisture or ventilation problem.
Recommended Paint Types for NZ Bathrooms
Water-Based Acrylic with Mould Inhibitors
This is the go-to choice for most NZ bathrooms. Water-based acrylics dry quickly, have low odour, and clean up easily. Look for products specifically labelled for wet areas or bathrooms.
- Resene offers their Resene Lumbersider and Resene X-200 range, and their specialist Resene Mould Killer primer is excellent prep before topcoating.
- Dulux produces a Dulux Wash & Wear bathroom range with mould-inhibiting properties, widely available at hardware stores.
- Wattyl has interior acrylic options suited to high-humidity areas — check their product selector for bathroom-specific recommendations.
Sheen Level Matters
| Sheen Level | Moisture Resistance | Ease of Cleaning | Best For |
|---|---|---|---|
| Flat/Matt | Low | Poor | Not recommended for bathrooms |
| Low Sheen | Moderate | Moderate | Small, well-ventilated bathrooms |
| Semi-Gloss | High | Good | Most bathrooms |
| Gloss | Very High | Excellent | High-moisture or poorly ventilated bathrooms |
For most NZ bathrooms, a semi-gloss finish strikes the right balance between moisture resistance and a pleasant appearance. Gloss is ideal for ceilings directly above showers.
Surface Preparation: The Most Important Step
Even the best mould-resistant paint will fail if applied over a poorly prepared surface. This is where many DIY jobs go wrong.
- Kill existing mould first. Never paint over active mould. Use a dedicated mould killer or a diluted bleach solution, scrub thoroughly, and allow the surface to dry completely. Products like Resene Mould Killer or similar fungicidal washes are designed for this.
- Sand and clean. Lightly sand glossy surfaces so the new paint can bond. Wipe down with a damp cloth and allow to dry.
- Apply a suitable primer. A moisture-resistant or anti-mould primer gives your topcoat the best possible foundation. This step is especially important on new plasterboard (GIB) or previously unpainted surfaces — check GIB's technical guidance for wet-area board recommendations.
- Check for leaks. If mould keeps returning despite good paint and ventilation, there may be a plumbing leak behind the wall. Fix the source before repainting.
Ventilation: Paint's Best Friend
No paint will perform well in a bathroom with no airflow. Make sure your bathroom has a working extractor fan — ideally one that runs for at least 20 minutes after a shower. BRANZ research consistently shows that ventilation is the single most effective way to reduce condensation and mould in NZ homes. Open windows where possible, and consider a heated towel rail to keep the room temperature stable.
How to Apply Bathroom Paint
- Use a short-nap roller (around 10 mm) for smooth walls and a quality synthetic brush for cutting in around edges.
- Apply two coats, allowing full drying time between coats as specified on the tin.
- Ensure the room is well ventilated during and after painting — open windows or run the extractor fan.
- Avoid painting in very cold or humid conditions, as this affects how the paint cures.
When to Call a Professional
If mould is widespread, deeply embedded in the wall, or keeps returning despite your best efforts, it's time to bring in a qualified painter. A professional can assess whether the issue is surface mould or a deeper moisture problem, recommend the right products, and deliver a finish that lasts. Persistent mould can also indicate issues with the building envelope or plumbing that may need a builder or plumber to investigate.
Note on restricted work: Painting itself is not restricted work in New Zealand, so homeowners can tackle it themselves. However, if fixing the mould problem involves touching plumbing (e.g., repairing a leaking pipe), that work must be carried out by a licensed plumber registered with the Plumbers, Gasfitters and Drainlayers Board. Similarly, installing or modifying an extractor fan involves electrical work that must be done by a registered electrician — check the Electrical Workers Registration Board to find a licensed professional.
You can find qualified local painters and tradespeople on tradedirectory.co.nz.