How to stop mould coming back in a rental bathroom
You cannot stop mould coming back in a rental bathroom by scrubbing alone, and you cannot re-waterproof a place you do not own. What works is managing the damp and the air every week: dry the wet surfaces, keep the air moving, and meet the spores in the air before they land and grow again.
This comes from experience. A Queensland wet season, the house sealed up against the heat, the same corner of the shower going black no matter what I did. Third Sunday in a row, same silicone, same bloom, same bottle of bleach. It did not matter how often I cleaned or what I cleaned with. It kept coming back.
The last national survey to measure it found almost 18% of Australian homes had mould or mildew (Coulburn and Miller, 2022). Renters cop the worst of it, because the one thing that would fix it, the waterproofing behind the tiles, is not yours to touch.
Why does mould keep coming back in a rental bathroom?
Mould is the fungus that grows on damp surfaces. It releases microscopic seeds called spores. They float in the air, land on the next wet patch, and grow. For the longer version, here is how mould spreads through the air in your home.
In a rental, the damp keeps getting fed: old waterproofing behind the tiles, grout gone porous, a shower that never fully dries. Wiping only removes the surface bloom. The spores are still in the air, and they land again the moment the room gets wet. So the fight is the air and the damp, not the renovation you cannot do.
How do you stop mould in a rental shower you cannot renovate?
You change the conditions, not the building. Going into the 2026 wet season, this is the routine I run. Squeegee or towel the walls after every shower. Leave the door open and the window cracked so the room dries. Then handle the air side, because that is where the spores travel.
This is what we built First Light for. It works both in the air and on surfaces on direct contact, meeting mould spores before they settle. It is lab tested, 99.2% reduction in black mould on direct contact, measured under the BS EN 13697 surface method.
Clove (eugenol) and Litsea Cubeba (citral) disrupt the ergosterol-rich cell membrane that black mould (Aspergillus niger) builds to grow, a mechanism described in a 2024 paper in Industrial Crops and Products.
There is a limit, though. A bottle in the room is not a substitute for airflow. If the room stays wet with nowhere for the damp to go, spores from outside land and start again.
Why won't the mould in my rental bathroom come off?
Because it is not sitting on top of the silicone. It has grown into it. Old silicone and porous grout are soft and slightly open, so the black stain sets down into the material where no cloth reaches. You can lift the surface growth, but the stain in badly grown-through silicone stays until the silicone is replaced, a cheap reseal or a job for the owner.
While the surface is what it is, keep the air handled. In a 2022 UNSW Sydney lab-chamber study (Antibiotics), essential-oil vapour cut 72% of viable Aspergillus spores in 10 minutes, in a study that used a similar but not identical blend. That is the part a renter can act on.
What can you do if your landlord won't fix the bathroom mould?
Report it in writing to the agent or owner, and keep dated photos of every bloom. In most Australian states, waterproofing and structural repairs sit with the owner, and mould from a building fault, a leak, failed waterproofing or a dead exhaust fan, is generally theirs to fix. Mould from everyday condensation is usually yours to manage. Photograph any mould at move-in so it is not taken from your bond later. This is general information, not legal advice: your state tenancy authority, such as NSW Fair Trading or the Queensland RTA, has the specifics.
While you wait on the repair, you are not stuck. You can still manage the air and the damp yourself, and see the testing behind that on the lab results on our proof page.
Why does mould keep coming back when the exhaust fan is broken?
A fan that does not run leaves humid air sitting in the room after every shower. That damp air condenses on the cold tiles and ceiling, and those wet surfaces are exactly where spores land and grow. A broken fan is part of the premises, so report it: repairing it is usually the owner's job.
Until it is fixed, open the window and leave the door open after showering, run a cheap plug-in fan to push the damp air out, and use a dehumidifier if you own one. First Light keeps meeting mould spores before they settle in the meantime. Be honest about the trade-off: it works alongside ventilation, not instead of it.
Bleach or First Light for a rental bathroom?
Most renters reach for bleach first. I did, every Sunday. But the US EPA's guidance on bleach and mould is blunt: it does not recommend bleach as a routine mould treatment. Verbatim: "The use of a chemical or biocide that kills organisms such as mold (chlorine bleach, for example) is not recommended as a routine practice." Bleach whitens the surface stain, but in a room where the real problem is damp air, that only gets you so far.
| What matters in a rental | Chlorine bleach | First Light |
|---|---|---|
| Where it acts | On the surface you can see | In the air and on contact, meeting mould spores before they settle |
| Routine daily use | EPA does not recommend it as a routine practice | Made for daily use in the room |
| What is in it | Chlorine | 100% natural, six pure essential oils, no fillers, no synthetic fragrance |
| Lab result | Not applicable | Lab tested under BS EN 13697 (see the lab result above) |
Nothing in a bottle beats a dry, ventilated room, and no renter should have to renovate to keep a bathroom in check. Manage the damp, move the air, meet the spores before they settle. For the full method, here is our full guide to stopping mould coming back.
Frequently asked questions
Can you get mould out of old bathroom silicone?
Old silicone that mould has grown into holds the black stain even after you clean the bloom off the top. A weekly routine keeps it from taking hold again, but badly grown-through silicone usually needs replacing, a cheap reseal or a job for your landlord.
Will my landlord pay to fix bathroom mould?
If the mould comes from a building fault, a leak or a dead exhaust fan, it is generally the owner's to repair. Report it in writing and keep dated photos. Everyday condensation is usually yours to manage, and your state tenancy authority has the detail.
Does managing the air actually help if the surface keeps getting wet?
Wiping removes what you can see, but spores keep floating and landing on the next damp patch. Meeting them in the air, drying surfaces, and keeping air moving is what keeps the bloom from coming straight back. If the room stays wet with no airflow, nothing in a bottle will hold it.
How often should I use First Light in a rental bathroom?
5-8 drops in a diffuser, 30-60 minutes daily, in the worst-affected room. It is 100% natural, six pure essential oils, no fillers, no synthetic fragrance, and it comes with a 60-day money-back guarantee. Keep the bottle. Reply with one photo, full refund, no return shipping.
For the full prevention method, see our guide to how to stop mould.
Ben, founder of Aurala Naturals. Last updated 2026.
Related guides
For more on managing mould as a tenant, see the renter's guide to mould in Australia. See also getting rid of rental bathroom mould without bleach.
