Key takeaways
- Mould in the workplace comes down to moisture plus poor airflow. Leaks, humidity, damp building materials and blocked ventilation cause almost every case.
- The usual hot spots are staff bathrooms, kitchens, storerooms, air conditioning systems and anything stacked against an external wall.
- Under WHS law, a business must identify and manage the risk mould poses to workers. Ignoring a known leak isn’t an option.
- Small surface patches can be cleaned in-house. Mould in HVAC systems, wall cavities or porous materials needs a professional.
- Prevention is cheaper than remediation: fix leaks fast, keep air moving and service the AC.
What Causes Mould in the Workplace?
Mould in the workplace grows wherever moisture builds up and air doesn’t move. In small businesses, these seven causes account for most of it.
1. Poor ventilation
When indoor air isn’t circulated, moisture levels rise. Bathrooms, storerooms, basements and back-of-house areas are the usual problem spots.
2. High humidity
Businesses in humid areas, or with kitchens, showers or laundries on site, are most exposed. Keeping indoor humidity below about 50% helps stop mould taking hold.
3. Water leaks and moisture intrusion
Roof leaks, burst pipes, blocked gutters and flooding bring water straight into the building. Slow leaks are often worse, because nobody notices them for months.
4. Damp building materials
Plasterboard, timber, carpet and ceiling insulation soak up moisture and stay damp, giving mould something to grow on.
5. Poor cleaning in wet areas
Kitchens, staff bathrooms and cleaning cupboards need regular cleaning and surfaces that get properly dried afterwards.
6. Skipped maintenance
Dirty air conditioning filters, unrepaired leaks and blocked drains all let moisture and mould build up over time.
7. Clutter and storage
Stock and cardboard stacked against walls block airflow and hide early growth until it’s widespread.
Where Mould Shows Up, by Type of Business
| Business | Common hot spots | Why |
|---|---|---|
| Offices | Air conditioning, ceiling tiles, carpet under windows | Condensation, roof leaks, sealed buildings |
| Cafes and restaurants | Cool rooms, dish areas, staff bathrooms | Constant steam and water use |
| Retail and storerooms | Stock rooms, cardboard against external walls | Little airflow, cold walls |
| Gyms and studios | Change rooms, showers, mats | Sweat, steam, wet surfaces |
| Childcare and healthcare | Bathrooms, sleep rooms, storage | Wet areas, and occupants who are more sensitive to mould |
| Warehouses | Roof lines, roller doors, pallets | Roof leaks, open doors in wet weather |
What WHS Law Expects of Business Owners
Under Australia’s work health and safety laws, a business must manage risks to workers’ health. Mould in the workplace is one of those risks.
WorkSafe ACT’s safety alert on moulds and indoor air contaminants spells it out: businesses must identify and manage the risk, and may need specialists to remediate it.
- Fix leaks and water damage quickly, and keep a record of what you did.
- Clean mould-prone areas regularly and keep ventilation working.
- Tell staff where mould has been found, and listen when they raise it.
- Bring in a specialist when growth is extensive or keeps coming back.
This is general information, not legal advice. Your state WHS regulator can confirm your specific obligations.
Early Warning Signs to Watch For
- A musty smell in storerooms, bathrooms or when the AC starts up.
- Black, green or white spots on ceilings, grout, silicone or behind furniture.
- Stained or sagging ceiling tiles.
- Bubbling paint or soft plasterboard.
- Staff mentioning headaches, sneezing or itchy eyes that ease when they leave the building.
Mould can trigger allergy and asthma symptoms. Victoria’s Better Health Channel explains who is most at risk.
How to Prevent Mould in Your Business
Preventing mould in the workplace costs far less than removing it. Most of it is routine maintenance.
- Fix leaks within days, not months. Check roofs, gutters and plumbing after heavy rain.
- Keep air moving. Run exhaust fans in bathrooms and kitchens, and don’t block vents.
- Control humidity. Use dehumidifiers in storerooms and other closed spaces.
- Service the air conditioning. Clean filters and drain trays on a schedule.
- Store stock off the floor and away from walls. Leave a gap so air can circulate.
- Clean and dry wet areas daily. The NSW Health mould fact sheet recommends a mild detergent or diluted vinegar for routine mould cleaning.
When to Call a Professional
A small patch on a hard surface can be cleaned in-house. Call a professional when any of these apply:
- The affected area is bigger than about a square metre.
- It’s in plasterboard, carpet, ceiling insulation or the air conditioning system.
- It keeps coming back after cleaning.
- It followed a flood, burst pipe or roof leak.
- Staff, customers or children with health concerns use the space.
Start with mould inspection and testing to find the source. For the clean-up itself, see how our commercial mould removal is staged for businesses that can’t close. Our guide to commercial mould cleaning methods explains the techniques used.
Why Businesses Choose AllAces
For a business, the clean-up has to fix the problem without shutting you down for a week.
- IICRC Certified Firm working to the ANSI/IICRC S520 standard for professional mould remediation.
- Work staged around trading. Areas are sealed and run under negative air, so the rest of the premises can usually stay open.
- Reports that stand up. Inspection reports written for insurers, landlords and strata managers.
- More than 35 years of restoration work, with teams in Sydney, Melbourne, Brisbane and Ballarat.
Workplace Mould FAQs
How much does professional mould removal cost for a business?
It varies with the size of the problem, the materials affected and how hard the area is to reach. Small jobs can cost a few hundred dollars, while large or complex cases can run into thousands. An inspection gives you an accurate scope before you commit.
Is mould removal covered by business insurance?
It depends on your policy and the cause. Mould from a sudden event, like a burst pipe, is more likely to be covered than mould from slow leaks or poor maintenance. Check with your insurer before work starts.
Can staff remove mould themselves, or should we hire a professional?
Small, isolated patches on non-porous surfaces can be cleaned by staff using proper precautions. Extensive growth, mould in HVAC systems or mould in porous materials should be handled by a professional.
Who is responsible for mould in a leased commercial premises?
Usually it depends on the lease and the cause. Landlords tend to be responsible for the building structure, roof and plumbing, and tenants for cleaning and ventilation in their space. Check your lease and raise it in writing early.
The Bottom Line
Mould in the workplace is a moisture problem before it’s a cleaning problem. Fix leaks quickly, keep air moving, service the AC, and act on the first musty smell. When it’s beyond a small patch, bring in a specialist, both for your staff and for your WHS obligations.
Related reading
About the Author: Nick Roth
With over six years at AllAces and extensive training and experience in mould remediation, Nick Roth is our most experienced Mould Remediation specialist and a national technical cornerstone. He leads on the most complex mould testing and structural remediation challenges, bringing deep expertise in specialised equipment like Hydroxyl machines to support field teams across the country.
