Mould grows where there is moisture. The paint did not cause it SafeWork NSWView source . Mould-resistant paint inhibits growth on a dry, prepared surface, but if the moisture source is still active, the mould will come back no matter what is on the wall Dulux TradeView source .
Before repainting makes sense, you need to know which problem you are actually dealing with: surface mould from condensation, or structural damp from a leak somewhere in the building.
Water stains work the same way. A dry, old stain is a painting problem. A fresh or spreading stain means water is still getting in, and paint applied now will not hold DuluxView source .
Two problems that look similar but need different fixes
Surface mould appears in bathrooms, kitchens and cool south-facing bedrooms. Condensation forms. Airflow is not enough to dry it SafeWork NSWView source . You will typically see dark spots in corners or around window frames. It gets worse in winter. It eases off in summer. If you fix the ventilation and the wall dries out, a painter can treat the area and repaint.
Structural damp is different. It spreads across more than one surface or room. It comes back within weeks of being painted over. Common causes include a leaking pipe, a failing roof or gutter, or rising damp coming up through the slab or brickwork Dulux TradeView source . A painter repainting structural damp without fixing the source first is money wasted: the mould will return.
Ask one question: does this mould appear seasonally in one spot, or does it keep spreading no matter what? If it keeps spreading, the moisture source needs attention before paint is even ordered SafeWork NSWView source .
Water stains on ceilings and walls: what's underneath matters
A water stain on a ceiling is a record. The question is whether the water is still there.
An old, dry stain from a past leak that has been repaired is a painting problem. Standard paint will not cover it: the discolouration bleeds through DuluxView source . A stain-blocking primer goes on first. Dulux PRECISION Stain & Mould Blocker blocks oil-based stains and inhibits mould growth, with a touch-dry time of 20 minutes and a recoat window of 2 hours . The same prep step shows up across manufacturers: Taubmans Fast Drying Stain Blocker is sold expressly for sealing persistent water-based stains on smoke- or water-damaged surfaces before the topcoat goes on TaubmansView source . That is the right sequence: seal, dry, paint.
A fresh stain is different. Still damp. Spreading. Appeared after rain. That means water is actively getting in, and paint applied now will not hold DuluxView source . The stain reappears (usually within a season) and the substrate often softens underneath. Fix the source first. Let the wall dry. Then call a painter.
What mould-resistant paint actually does (and where it stops)
Mould-resistant topcoats contain antimicrobial additives that inhibit mould and mildew growth on the painted surface. They work. Dulux Wash&Wear +PLUS Kitchen & Bathroom carries Mouldshield Technology and a 10-year guarantee against mould growth when correctly applied to a prepared, dry surface DuluxView source .
The guarantee has a condition built into it. The surface must be correctly prepared: removing existing mould, using a compatible primer on porous or stain-affected areas, and addressing any ventilation issues in the room Dulux TradeView source . Painting over existing mould or an untreated stain does not activate the resistance.
Think about a bathroom exhaust fan that barely works. Mould-resistant paint will slow the return. But it will not stop it. Fixing the fan stops it. Paint is the last step, not the only one SafeWork NSWView source .
When to call a painter, and when you need more than a painter
A licensed painter can treat mould, apply a stain-blocking primer, and repaint. For surface mould in a room where the moisture source has already been fixed, that is the right call. Both Dulux and Taubmans specify the same prep sequence: clean with a bleach-based cleaner, rinse thoroughly, prime with a mould-blocking primer, then apply the mould-resistant topcoat TaubmansView source .
But the painter should not always be the first call. Significant mould across multiple locations warrants a mould removal specialist before any painting begins. Dulux Trade guidance is explicit about this Dulux TradeView source . Painting over widespread mould without specialist treatment is not a lasting fix.
A hidden source is also a specialist problem. If you can smell mould but cannot find it, or it keeps returning on walls that were never visibly wet, SafeWork NSW notes that investigating mould is best left to an experienced professional with specialised equipment, and that specialist sampling may be needed where the source is unclear SafeWork NSWView source . Structural causes (a leaking pipe, a failing roof) need a plumber or builder first. The sequence matters: fix, dry, then paint.
Not sure which situation you are in? Describe the full picture to a licensed painter. They will tell you if another trade needs to go first. You can also read about cracked or damaged plaster in the Paint problems and prep guide, or look into what causes paint peeling and blistering if that is happening alongside the mould.
If your home was built before 1970, one extra step
Australian homes built before 1970 commonly used lead-based paint.NSW EPAView source NSW HealthView source Lead is a health hazard: even low-level exposure can affect children's development.
Sanding or scraping old painted surfaces can release lead dust, so before any mould or stain repair on pre-1970 walls, test the surface (or, if you can't test, assume it's contaminated) and keep children and pregnant women away while paint is disturbed.NSW EPAView source NSW HealthView source A licensed painter working on older homes can advise you on the risk, so raise it when you describe the job.
What does a mould treatment and repaint cost?
The cost depends on the size of the affected area, the extent of prep required, and whether specialist mould treatment is needed before the painter starts. SureQuote's patch-and-paint estimates give you a live range based on your specific job.
Common questions about mould, stains and painting
Mould returns because the moisture source is still active, not because of the paint. SafeWork NSW is explicit: unless you fix the underlying water, excess moisture or ventilation problem, the mould problem will return SafeWork NSWView source . So fix the source first Dulux TradeView source . Improve the ventilation. Repair the leak. Fix the plumbing fault. Then a licensed painter can treat the existing mould and apply a mould-resistant topcoat on a properly prepared, dry surface DuluxView source . Without fixing the moisture, no topcoat will stop it returning.
Mould-resistant topcoats contain antimicrobial additives that inhibit mould growth on the surface. Dulux Wash&Wear +PLUS Kitchen & Bathroom carries Mouldshield Technology and a 10-year guarantee against mould growth when correctly applied DuluxView source . Taubmans offers the same kind of product. Its Easycoat range uses Bacteria Shield antimicrobial technology to inhibit mould, mildew and fungus, and is marketed for bathrooms, kitchens and other damp areas TaubmansView source . 'Correctly applied' means the surface is dry, existing mould has been removed, and a compatible primer has been used first. On a surface with active moisture, no paint will reliably stop mould from returning.
Standard paint will not cover a water stain: the discolouration bleeds through. A stain-blocking primer goes on first. Dulux PRECISION Stain & Mould Blocker is a water-based primer that blocks oil-based stains and inhibits mould DuluxView source . Touch-dry in 20 minutes. Ready for topcoat in 2 hours. Taubmans sells an equivalent prep coat. Its Fast Drying Stain Blocker seals persistent water-based stains on smoke- or water-damaged surfaces before the topcoat TaubmansView source . Apply the primer to the stained area, let it dry fully, then paint over. If the stain is still damp or spreading, fix the source first. Priming over active moisture will not hold.
Ready to treat the mould and repaint?
SureQuote connects you with licensed painters who handle mould treatment, stain-blocking primer and repaint as a single job. Tell us what's on the wall (ceiling, bathroom, bedroom) and get quotes from painters in your area.
Sources
This page draws on manufacturer technical guidance (Dulux, Taubmans), SafeWork NSW regulator guidance on mould, and live SureQuote pricing data. The DCCEEW lead-paint reference could not be re-fetched this session (the URL timed out) and is flagged verified:false; its claim is treated as attribution only. This page contains general information and is not a substitute for advice from a licensed painter, mould removal specialist, or other trade professional.
- SafeWork NSWView source
- Dulux TradeView source
- DuluxView source
- TaubmansView source
- DuluxView source
- TaubmansView source
- NSW EPAView source
- NSW HealthView source
- TaubmansView source