Why Mould Appears on Melbourne Homes
Melbourne's mix of coastal salt air and older housing stock creates ideal conditions for mould. In bayside suburbs like Mentone, Sandringham, and Mordialloc, salt-laden air combines with weatherboard cladding to trap moisture. In leafier, older pockets like Hawthorn, Malvern, and Armadale, period homes with cold masonry walls and limited ventilation are especially prone to condensation-driven mould.
The most common places we find mould are bathroom and laundry ceilings, external render on shaded or south-facing walls, eaves and fascias, bedroom corners with poor airflow, and weatherboard cladding exposed to persistent damp.
The Right Way to Treat Mould Before Painting
Skipping proper treatment is the single biggest reason mould returns after a repaint. The process below is what we follow on every mould-affected job, from a single bathroom ceiling to a full exterior repaint.
Step 1: Identify the moisture source — mould only grows where there is a persistent moisture source, so find and fix the cause before treating the surface.
Step 2: Kill the mould — treat with a bleach solution diluted 1:4 with water, or a purpose-made product such as Zinsser Mold Killing Primer or Dulux Mouldshield. Heavy mould may need substrate replacement.
Step 3: Allow complete drying — 24-48 hours before priming or painting, so moisture isn't trapped under the new coating.
Step 4: Prime with an anti-mould primer — Zinsser BIN Shellac Primer or Dulux Mouldshield Primer seals staining and inhibits future growth before the topcoat goes on.
Which Paint to Use on Mould-Prone Surfaces
The right topcoat depends on the surface and its exposure. Bathroom ceilings do best with Dulux Mouldshield or Taubmans Bathroom & Kitchen. South-facing external render should use Dulux Weathershield Maximum. Weatherboard exteriors hold up well with Dulux Weathershield or Taubmans All Weather. Bedroom walls prone to condensation are best treated with Dulux Mouldshield Interior.
How Long Does Anti-Mould Paint Last?
Properly treated and painted surfaces, with the moisture source fixed, resist mould far longer than surfaces simply painted over. High-moisture areas like bathrooms with poor ventilation tend to need attention again sooner, even with the right products, simply because of how much moisture the space handles daily.
When to Call a Professional
Mould covering a large area, mould that returns quickly after cleaning, staining that keeps bleeding through fresh paint, or any suspicion of a hidden leak or structural moisture problem are all signs it's time to bring in a professional rather than treat it yourself.
Jetblack Painting services Melbourne's southeast, Bayside, inner east, and Mornington Peninsula, and every job comes with a 5-year written workmanship guarantee.
Frequently Asked Questions
Can I just paint over mould instead of treating it?
No. Painting over mould without killing it first guarantees it comes back — usually within 3 to 12 months — turning a fresh paint job into a blotchy, failed surface. The mould spores are still there under the paint even if you can't see them.
How long does anti-mould paint last?
It depends far more on the room than on the paint. Where the moisture source has been fixed and the surface was properly treated before painting, mould usually stays away. Where the cause is still there, such as a bathroom with no working exhaust fan, it will come back sooner and the surface will need treating again.
When should I call a professional instead of treating mould myself?
Call a professional when mould covers more than 1 square metre, it's on external render or masonry, it has returned after previous DIY treatment, there's visible substrate damage like soft plaster or rotted timber, or the moisture source is unclear.
What primer actually stops mould coming back?
Standard primers won't prevent regrowth. A dedicated anti-mould primer — we use Zinsser BIN Shellac Primer or Dulux Mouldshield Primer most often — seals the surface and includes fungicides that inhibit mould, which is essential on bathroom ceilings and external render with a history of mould.