How to get rid of mould on walls (and keep it away)
Published by Aurala Naturals. Last updated 2026.
To get rid of mould on walls, fix the moisture before you touch the stain: a cold wall gathering condensation, a hidden leak, or rising damp. Then clean the surface gently so you lift the spores rather than spread them, let the wall dry fully, and keep it ventilated and warm so the growth does not return.
Why does mould grow on your walls in the first place?
Mould is a living growth, and it needs three things to spread: moisture, something to feed on, and still air. A wall offers the food and the still air for free. Paint, plaster, dust, and the thin film of soap or cooking grease that settles on a surface are all it needs to eat. The one thing you actually control is the water. That is why wiping mould off a damp wall almost never holds for long: within a few weeks the surface is wet again and the growth comes straight back. Getting rid of it is really two jobs done together, cleaning what you can see and drying out the wall so it stops feeding the next patch.
How do you find the moisture source behind the mould?
Before you clean anything, work out where the water is coming from, because that decides whether a clean will hold. On walls there are three usual sources, and each leaves a different clue. Read the pattern of the mould and it will point you to the cause.
The most common is condensation on a cold wall. Warm, moist indoor air meets a cold surface, the water in that air turns back to liquid on the wall, and mould settles on the damp film. You tend to see it as fine black spotting on the coldest parts of the room: the corners where two outside walls meet, the wall behind a wardrobe, and the edges around windows. If that sounds like your wall, the mechanics of how condensation forms at the dew point explain why those cold spots collect water first.
The second is a leak. A pipe inside the wall, a roof or gutter fault, or failed flashing feeds one area with water it should never get. The tell here is a defined damp patch that stays wet even through a dry spell, often with a stain that spreads outward from a single point. A leak will beat any amount of cleaning until the plumbing or the roof is fixed.
The third is rising damp, where ground moisture is drawn up through masonry from below. It shows as a tide line low on the wall, usually up to about a metre high, sometimes with a chalky salt residue where the water has evaporated and left minerals behind. If your mould sits in a band near the skirting rather than up in the corners, read up on how rising damp behaves in Australian homes before you spend money on the wrong repair.
How do you clean mould off painted walls and plaster safely?
Once you know the moisture is under control, clean the wall in a way that lifts the growth instead of flinging it around the room. The single biggest mistake is dry-brushing or dry-wiping, which throws spores into the air to settle somewhere else. Work damp, work gently, and work in fresh air.
- Open a window and, if you have one, run an exhaust fan so moving air carries loose spores outside rather than around the house.
- Put on gloves and dampen the mouldy area first with a spray bottle of water, so nothing lifts off as dry dust.
- Wipe in one direction with a disposable cloth or paper towel. Do not scrub back and forth, which grinds spores into the paint and spreads them sideways.
- Turn to a clean section of cloth often, and change cloths well before they look saturated.
- Bag the used cloths and seal the bag before it leaves the room.
- Let the wall dry fully before you decide whether it needs anything more.
Bleach is most people's first reach for mould, but it has real limits. It often lightens the stain so the wall looks clean, yet on porous plaster the growth sits below the painted surface, and the whitening can hide how far it really spread. For painted walls and skirtings you clean often, warm water with a little detergent lifts the surface growth gently and leaves no chlorine smell behind. Whatever you use, the clean only holds if the wall underneath is dry.
Is the paint just stained, or is the wall damaged underneath?
After cleaning, judge whether you are looking at a surface stain or a compromised wall, because they need very different fixes. Press the plaster with a fingertip. If it is firm and simply discoloured, the paint is sound and the mould sat on top. A faint grey shadow that will not wash out is just staining, and a stain-blocking primer followed by a repaint will cover it. The wall itself is fine.
The other case is a surface that has been wet for a long time. The signs are plaster that feels soft or gives under light pressure, paint that bubbles or peels, a patch that stays cool and musty however long you wait, or growth that has clearly gone into the plasterboard rather than sitting on the paint. Here, cleaning the face of the wall will not solve it, because the material behind is still wet and still feeding the growth. That section has to dry out fully, or be cut out and replaced, and the moisture source has to be fixed first. Painting over damp, compromised plaster simply traps the water, and the mould pushes back through the new coat.
Which walls in your home are most likely to grow mould?
Some walls are simply at higher risk, and knowing which ones lets you catch a patch early. External walls are the usual trouble, especially those that face south or sit in permanent shade and never warm up. Corners where two outside walls meet are colder still, as are the wall areas hidden behind large furniture pushed hard against an external wall, where air cannot move. Windows, bathrooms, laundries, and any room built on or below ground level all tend to run damp. For a walk through the spots that catch people out, the room-by-room guide to where mould hides covers each space in turn.
How do you stop mould coming back on the same wall?
Cleaning gets rid of what is there today. Keeping the wall clear is about not letting it get wet again, which comes down to three things: ventilation, warmth, and keeping water out.
The first is ventilation: get moist air out before it can settle on a cold wall. Run exhaust fans in the bathroom and kitchen, open windows after showering or cooking, avoid drying washing indoors without airflow, and leave a few centimetres between big furniture and external walls so air can move behind it.
The second is warming the cold spot. Condensation forms where the wall surface is coldest, so anything that raises that surface temperature helps: insulating the problem wall, or keeping the room's warmth steadier through the day, lifts the wall above the point where water condenses on it. A wall that stays warmer stays drier.
The third is simply keeping water out: fix leaks promptly, keep gutters and downpipes clear, and deal with rising damp at its source rather than the symptom. A hygrometer to watch indoor humidity, and a dehumidifier through the worst months, both help hold the balance. For the full picture across the whole house, the Australian guide to stopping mould before it starts pulls ventilation, heating, and moisture control together.
No clean is a one-time fix. A wall stays clear only for as long as it stays dry, so treat this as ongoing upkeep rather than a single job. Fix the moisture and the maintenance becomes light. Ignore it, and you will be back with a cloth every few weeks.
Once the wall is clean and dry, First Light helps stop new growth taking hold on a surface that tends to run damp. It is a 100% natural Australian six-oil essential-oil blend for mould defence, not a cleaner, so it goes to work after you have cleaned rather than in place of it. The main way to use it is in a diffuser: the oils spread through the room and meet spores before they settle, so mould is slower to return between cleans. It also works on direct contact, so you can put a few drops in 250ml of water and lightly mist the now-clean wall. Lab tested: 99.2% reduction in black mould on direct contact. You can find it alongside the waterless diffuser that runs it in our range.
