How to stop mould in a rental without a dehumidifier

Published by Aurala Naturals. Last updated 2026.

You do not need a dehumidifier to slow mould in a rental. Open two windows for cross-flow air, run the existing exhaust fans longer, dry washing outside, and squeegee wet surfaces. Watch humidity with a few-dollar hygrometer, and report broken fans or leaks to your landlord in writing.

Can you stop mould in a rental without a dehumidifier?

Mould needs three things to grow: moisture, a surface to feed on, and still air. In a rental you usually cannot rebuild the walls or replace the windows, so the two things you can change are the moisture and the airflow. A dehumidifier pulls water out of the air, and it works, but it is not the only tool and it is far from the cheapest. The real job is simpler than buying an appliance. You want everyday moisture to leave each room faster than it builds up. Cooking, showering and drying clothes all add water to the air. If that water lands on a cold wall or window and sits there, mould has what it needs. Stop the water from settling, move the air, and you take away the conditions mould depends on. Most of the methods that do this cost nothing. For the wider picture, see our full guide to preventing mould in Australian homes.

What free methods actually reduce moisture indoors?

The cheapest tools are the windows and fans you already have. The single most effective free habit is cross-flow ventilation: open two windows on opposite sides of the room or home so air moves through instead of sitting still. Ten minutes of a through-breeze in the morning clears out the damp air that built up overnight. Beyond that, a handful of small habits add up.

• Run the existing exhaust fans in the bathroom and kitchen for longer, ideally fifteen to twenty minutes after a shower or a big cook, not just while you are in the room.
• Squeegee the shower walls and glass after every wash, and wipe down window sills where condensation collects overnight.
• Dry washing outside on a line whenever you can, because a single load dried indoors can release litres of water into the air.
• Keep furniture a few centimetres off external walls so air can move behind it, since the backs of wardrobes on cold walls are a classic mould spot.
• Open wardrobe doors and pull back curtains during the day to let light and air reach the corners that stay closed and still.
• Put lids on pots while cooking and use the rangehood to trap steam before it spreads through the home.

None of these cost a cent, and together they cut the moisture load enough that mould struggles to get started.

Does opening the windows in winter just let cold, damp air in?

This is a fair worry, and the answer is that short bursts of ventilation help even in winter. It sounds backwards, but cold outdoor air holds less moisture than the warm, humid air inside a closed-up home. When you let that cold air in and then warm it, its relative humidity drops, so it can soak up moisture from the room before you air it out again. The trick is to ventilate in short, sharp bursts rather than leaving a window cracked all day. Open two windows wide for five to ten minutes, let the through-breeze flush the stale air, then close them and let the heating bring the room back to temperature. Doing this a couple of times a day moves far more moisture out than a window left ajar all day, and it wastes less heat. The mornings matter most, because a night in a closed room adds a surprising amount of water to the air, so a quick morning flush sets the room up for the day.

What cheap tools help you keep humidity down?

If you want to spend a little, two cheap items do most of the work of an appliance. The first is a hygrometer, a small humidity gauge that costs a few dollars. It takes the guesswork out of the problem by showing you the moisture in the air as a number. Aim to keep indoor humidity below about 60 percent. When the reading climbs, you know it is time to open a window or run a fan. Watching the number for a week also shows you which rooms and which times of day are worst, so you can target them.

The second is a set of moisture absorbers, the small tubs of crystals sold in supermarkets and hardware shops. These are not a whole-room fix and they will not replace ventilation, but they are genuinely useful in small, closed spaces where air does not move: a wardrobe, a linen cupboard, a bathroom vanity or a rarely opened drawer. Place one where clothes or towels feel damp, and refill it when the tub fills with water. Between a hygrometer and a few absorbers you have covered the two things a dehumidifier does, for a fraction of the price.

When should you tell your landlord about a mould problem?

Habits and cheap tools manage the moisture you create. They cannot fix a building fault, and that is where your landlord comes in. If the water is coming from the building itself, no amount of airing out will keep up. Report the problem in writing, by email or through your property manager, so there is a dated record, even if you have already mentioned it in person.

• An exhaust fan that does not work, or one that vents into the roof space instead of outside.
• Window or door seals that have failed and let condensation pool on the frames.
• Signs of rising damp, such as a tide mark low on an internal wall.
• Any leak from plumbing, the roof or the gutters that leaves a wall or ceiling wet.

In most Australian states a landlord is responsible for keeping a property in a reasonable state of repair, and unresolved damp from a building fault usually falls to them. If mould keeps returning in one wet room despite your best habits, that is a strong sign of a fault worth reporting. Our guide to why mould keeps coming back in a rental bathroom walks through the usual culprits.

How do you handle the spots that keep coming back?

Even with good habits, a few spots tend to return: the grout line in the shower, the corner of a window, the back of a wardrobe. For these, a simple weekly routine keeps regrowth in check between the bigger jobs. Clean off what you can see with your usual method, let the surface dry fully because a damp surface just invites the next patch, and then add a defence step to make it harder for mould to settle back.

A natural essential-oil blend is a practical option for that defence step. Once the spot is clean and dry, Aurala's First Light, a six-oil blend made in Australia, is designed to keep mould from settling back rather than to clean it off. It is not a cleaner, so you diffuse it in the room, leave a few drops on a dish in an enclosed spot like a wardrobe, or mist a few drops in water over a surface you have already cleaned. Independent lab testing showed a 99.2% reduction in black mould on direct contact, and it works both in the air and on the surfaces it touches. First Light is 100% natural and made for daily use around kids and pets; dilute as directed, spot-test the surface first, and ventilate while you work.

Be honest with yourself about what this routine can and cannot do. Cleaning clears what you can see and First Light helps keep the spot from returning, but neither removes the moisture that fed the mould in the first place. If the same spot keeps returning within days, the answer is not more product, it is finding and fixing the water behind it: a fan, a seal, or a leak.

You do not need to spend much to make real progress on mould in a rental. Start with the free habits, add a cheap hygrometer to see what is working, and report anything the building itself is doing wrong. Fix the moisture first, keep the recurring spots in check, and the rest gets much easier.

Common questions

Can you really stop mould without a dehumidifier? Yes, for most everyday damp. A dehumidifier removes moisture from the air, but so does cross-flow ventilation, running exhaust fans longer, drying washing outside and squeegeeing wet surfaces. These free habits often keep humidity low enough that mould struggles to grow. A dehumidifier only becomes necessary when a room stays damp despite good airflow, usually because of a building fault.

What humidity level stops mould from growing? Mould generally needs relative humidity above about 60 to 70 percent at a surface to take hold. Keeping indoor humidity below roughly 60 percent makes it much harder for mould to establish. A cheap hygrometer lets you watch the number and act when it climbs, opening a window or running a fan before the air gets damp enough for mould to settle on cold walls.

Do moisture absorbers work as well as a dehumidifier? Not for a whole room. The tubs of crystals sold in supermarkets pull a small amount of water from the air and work best in small, closed spaces like a wardrobe, a cupboard or a bathroom vanity where air does not move. They are a cheap helper, not a replacement for ventilation. Use them alongside open windows and fans rather than instead of them.

Whose job is it to fix mould in a rental, mine or the landlord's? It depends on the cause. Moisture you create through cooking, showering and drying clothes is yours to manage with airflow and habits. Damp from a building fault, such as a broken exhaust fan, failed seals, rising damp or a leak, is usually the landlord's responsibility to repair. Report faults in writing so there is a dated record, and keep managing everyday moisture in the meantime.