Mould on a wall is a symptom with a location. Kill the growth without changing what made the wall damp and it will be back within a season, usually in the same corner, which is why the useful question is not which product to buy but which wall is staying wet.
Why it keeps coming back
Mould needs spores, a food source and moisture, and the first two are always present in a building. Removing the visible growth without fixing the moisture source guarantees a return, so treat the leak, the condensation or the ventilation first, then kill and remove what is growing.
Prices are Freshway catalogue prices as at 16 September 2026 and are subject to change. Confirm the current price, and whether GST applies, before quoting.
First, find the water
Four causes explain almost every mould call we get:
- Condensation on a cold wall. The common one. Insulation missing, a wardrobe pushed against an external wall, or a bathroom with no extraction.
- A slow leak. A gutter, a flashing, a failed shower seal or a dripping pipe inside the cavity. The mould appears at the edge of the wet zone, not directly under the leak.
- Rising damp. A band along the bottom of the wall, usually with a tide mark.
- Flood or spill that was not dried within 24β48 hours. This is a drying job with air movers and dehumidifiers, not a cleaning job.
If the wall is actively wet, drying it comes first. Our air movers and carpet dryers and dehumidifiers ranges are the equipment side of that job.
Removing black mould from painted walls
Painted plasterboard is the surface people ask about most, and it is also the easiest to damage. The method that works without stripping the paint:
- Put on gloves, eye protection and a P2 respirator, and ventilate the room.
- Apply a mouldicide to a cloth or sponge β not a spray that mists spores into the air. Work in sections no larger than a square metre.
- Wipe with light pressure, turning the cloth often. Do not scrub dry, and do not use a brush on painted plasterboard.
- Rinse with clean water and dry the wall completely. A fan on the surface for a few hours does more than a second chemical pass.
Bleach kills surface mould but leaves the staining and the dead growth behind, and the stain reads as mould to anyone looking at the wall. A combined mouldicide and destainer is why products like Mould Exterminator exist.
The products we stock, and what each is for
| Product | Job | Price |
|---|---|---|
| Freshway Mould No More 333 | Everyday mould removal on walls, tiles and ceilings | A$27.00 |
| Actichem Mould Exterminator | Mouldicide plus destainer, 5Β L trade size | A$29.00 |
| Actichem Mould Remover | Mould remover and sanitiser for sensitive sites | A$58.00 |
| Actichem Percide | Decontaminant and destainer for heavy growth | A$80.00 |
| Actichem Biosan II | Hospital-grade disinfectant, ready to use | A$35.00 |
Ceilings, timber and grout lines
Ceilings behave the same way but are harder to reach and usually wetter, because warm humid air rises and condenses there. Work with a long-handled applicator and a drop sheet, and expect the ceiling in a bathroom to need extraction before it needs another chemical clean.
Timber and unsealed surfaces absorb the stain, so chemical removal reaches a limit. Where the mould has gone into a timber window frame or a skirting board, the honest answer is to replace the affected timber, not to keep treating the surface.
Safety, and one thing to check first
Mould work is respirator work. Disturbing a dry colony releases spores, and the airborne dose is what causes the cough that people notice afterwards. Gloves, eye protection, ventilation and a P2 mask are the minimum, and SafeWork NSW covers the controls under chemicals and other substances.
In any building constructed before the mid-1980s, check for asbestos before you scrape, sand or cut into a wall, ceiling or eaves lining. SafeWork NSW publishes the asbestos guidance that applies here, and a $30 test kit is cheaper than a removal job.
Questions we get asked most
- How do you get rid of mould on walls permanently?
- By removing the moisture that feeds it. Kill and remove the growth with a mouldicide and destainer, then fix the condensation, leak or ventilation problem; without that step the mould returns regardless of which product you used.
- How can I remove black mould from painted walls?
- Apply a mouldicide to a cloth rather than spraying, wipe in small sections with light pressure, then rinse and dry the wall. Avoid brushing painted plasterboard, and allow the wall to dry fully before repainting.
- Is mould inside walls harmful?
- Mould growing inside a cavity indicates ongoing moisture, which damages the structure regardless of the spores. If you can smell it but cannot see it, treat it as a building problem and find the water before treating the surface.
- Is it safe to wipe mould off walls?
- With gloves, eye protection and a P2 respirator, and with ventilation, yes. The risk is airborne spores, so wipe rather than brush or dry-scrape, and never sand a mouldy surface without extraction.
- Do I need to repaint after treating mould?
- If the growth was heavy, yes β the stain often remains in the paint film. Use a mould-resistant or stain-blocking primer and fix the moisture source first, otherwise the new paint will fail in the same place.
References
- SafeWork NSW β asbestos guidance.
- SafeWork NSW β chemicals and other substances.
- NSW Environment Protection Authority β chemical handling and disposal.
Not sure whether it is a cleaning job or a building job?
Send a photo and tell us where on the wall it is and whether the wall feels damp. We will tell you honestly whether to treat it or to call someone about the moisture first. Browse cleaning chemicals or ask our team.