Does mould-resistant paint actually work?
27 June 2026 · 3 min read
It works, within limits that the marketing does not make clear. What the additive does, how long it lasts, and what it cannot fix.
Mould-resistant paint is a real product doing a real thing. It is also routinely sold as a solution to a problem it can only slow down.
What is actually in it
These paints contain a **fungicide** or **biocide** in the film. As mould spores land on the surface, the additive inhibits their ability to establish and grow.
Two things follow from that, and they are the whole story.
First, it acts **on the paint film only**. It does nothing about mould in the substrate behind, in the grout, in the silicone, or in the ceiling cavity.
Second, the additive is **consumed and leached over time**. Every wash, every wipe-down and every cycle of condensation removes a little. Effective life is typically a few years, not the life of the coating. The paint keeps looking fine long after its mould resistance has gone.
Where it genuinely helps
- Bathrooms and ensuites with adequate but imperfect ventilation
- Laundries
- Kitchen splashback surrounds and behind appliances
- South-facing rooms in older Perth houses that stay cool and damp in winter
- Wardrobe interiors and behind furniture on external walls
- Rental properties, where you cannot control occupant behaviour
In each of these, the additive buys time and reduces how often you are cleaning.
Where it will not save you
A fan is worth more than the paint
A bathroom with no extraction, or with an extractor venting into the roof space rather than outside, will grow mould through any coating on the market. The paint slows the surface colonisation; the moisture load is unchanged.
It will not fix:
- Missing or ineffective mechanical extraction
- An extractor discharging into the roof cavity
- A plumbing or roof leak
- Rising damp or penetrating damp
- Condensation from a structural cold bridge
- Mould already living in the substrate underneath
Preparation is most of the result
Painting over existing mould with a mould-resistant product fails, because the colony under the film keeps growing and pushes through.
The correct sequence:
- **Kill it.** Use an appropriate fungicidal wash and give it the stated contact time — this is where most people fail, scrubbing immediately instead of letting the solution work.
- **Remove it.** Wash off the dead growth and the staining.
- **Dry the surface completely.**
- **Fix the moisture source.** Ventilation, leak, or drainage. Without this, everything above is temporary.
- **Prime** where staining persists, with a stain-blocking primer.
- **Coat** with the mould-resistant system.
What to do instead, or as well
**Extraction.** A fan sized for the room, ducted to outside, on a run-on timer so it keeps going after the shower. This is the single highest-value intervention in a Perth bathroom and it costs less than repainting the room.
**Heat and airflow.** Mould needs sustained surface moisture. Perth winters are mild but damp, and a closed-up south-facing room in July is a good place to grow it.
**Leave a gap.** Furniture hard against an external wall creates a cold, still pocket. A few centimetres makes a measurable difference.
**Wipe the shower down.** Unglamorous, and it works.
The honest verdict
Buy it for wet areas. It is a modest premium over standard paint and it earns it. Just do not buy it *instead of* fixing ventilation, because in that trade you will be repainting the same ceiling in two years.