Water Damage Restoration Melbourne has been helping local homeowners and families across Melbourne not just clean away mould, but figure out why it’s there in the first place. With over 20 years of experience, we will help you fix it so it doesn’t come back.
In this article, we’ll explain why mould shows up in houses, what areas are most at risk, how professionals treat it properly, and simple steps you can take to prevent it in the future. If you’ve ever wondered why your walls get damp spots, why your bathroom smells musty, or why mould keeps returning no matter how much you clean, keep reading; this will help.
Key Takeaways:
- Common triggers for moulds to grow include leaks, condensation, poor ventilation, rising damp, and past floods.
- Surface cleaning isn’t enough, and the root moisture source must be fixed to stop mould from returning.
- Use moisture meters, thermal cameras, and air tests to detect unseen dampness and spores.
- Install mould-resistant plasterboard, waterproof membranes, and exhaust fans in damp areas.
- Fix leaks fast, run dehumidifiers, ventilate rooms, and inspect after storms or floods to prevent mould regrowth.
What Is Mould and Why Does It Grow in Homes?
Mould is a fungus that thrives on damp surfaces inside buildings. It spreads through microscopic mould spores, which are present in indoor and outdoor air. When these spores land on moisture-prone materials like timber, plasterboard, carpet, or even dust, they begin to grow and colonise.
Key factors that support mould growth include high humidity levels, water leaks, condensation, poor ventilation, rising damp, and previous flooding. For example, water leaking behind bathroom walls, kitchen cabinets, or from roof damage creates hidden dampness where mould can establish. Without airflow from exhaust fans or natural ventilation, moisture stays trapped, increasing the risk.
Once established, mould can silently spread through building materials, HVAC systems, and insulation, sometimes without visible signs until damage becomes significant. Importantly, surface cleaning with bleach or sprays does not eliminate the root cause, only removing the underlying moisture source and improving indoor air quality can stop recurrence.
Studies show that indoor dampness and mould are associated with a 30–70% increase in respiratory symptoms, asthma, and allergies.
Common Causes of Mould in Homes
Understanding why mould appears in homes starts with knowing the typical moisture sources and building vulnerabilities where it thrives.
1. Leaking Pipes
Hidden water leaks under bathroom sinks, inside wall cavities, or behind showers create persistent dampness, ideal conditions for mould colonisation.
2. Roof Leaks or Blocked Gutters
Damaged roofing materials or clogged gutter systems let water infiltrate ceilings, attics, and wall insulation, setting the stage for hidden mould growth.
3. Condensation on Windows and Walls
When humid indoor air meets cold window panes or plasterboard walls, condensation forms. This moisture seeps into timber frames, paint layers, or gypsum boards, feeding mould.
4. Poor Ventilation
Areas like bathrooms, laundries, and kitchens lacking exhaust fans or cross-ventilation trap moisture, raising relative humidity and increasing mould risk.
5. Rising Damp
In older homes, ground moisture rises through brickwork or concrete foundations by capillary action, dampening walls and floors, perfect for mould development.
6. Flood or Storm Damage
After severe weather events or flooding, soaked carpet underlays, floorboards, and hidden spaces remain damp long after surfaces look dry, allowing mould to establish.
7. HVAC and Air Conditioning Systems
Poorly maintained HVAC ducts, air filters, or evaporator coils accumulate dust and moisture, creating an internal environment for mould spores to multiply and spread throughout the house.
How Professionals Find Out What’s Causing the Mould
At Water Damage Restoration Melbourne, mould remediation isn’t just about surface cleaning, it’s about identifying the underlying cause to prevent recurrence.
Here’s how professional mould inspectors diagnose the issue:
1. Moisture Meters
These devices detect hidden moisture pockets in walls, ceilings, flooring, and timber frames, identifying damp spots invisible to the eye.
Moisture meters detect elevated moisture levels in building materials, typically using a safe electrical resistance method. For example, timber with a reading above 20% moisture content signals a high risk for fungal decay, while masonry should remain below 5% moisture by weight to prevent capillary rise issues.
2. Thermal Imaging Cameras
Using infrared technology, these cameras reveal temperature differences that signal moisture behind plasterboard, insulation, or inside wall cavities.
3. Humidity Checks
Technicians measure indoor relative humidity to determine if the air is overly moist, a key factor in supporting mould growth.
Technicians use hygrometers to keep indoor humidity between 30–50%. Levels over 60% raise the risk of condensation and mould, especially without ventilation. The EPA recommends humidity control as key to mould prevention.
4. Air Quality Testing
Air sampling devices check for elevated levels of mould spores in the indoor environment, especially useful when contamination is suspected in HVAC systems or hidden spaces.
By combining these diagnostic tools, professionals assess whether you’re facing a surface-level issue or a deeper structural moisture problem, guiding targeted remediation and prevention strategies.
See How We Diagnose Hidden Moisture ➔How Professionals Treat Mould (Not Just Clean It)
Effective mould remediation involves more than surface cleaning, it requires addressing both contamination and moisture control to stop regrowth.
1. Safe Removal
Professionals use HEPA vacuums, air scrubbers, and antifungal treatments to remove mould colonies from walls, ceilings, carpets, and HVAC systems without releasing harmful mould spores into the air.
2. Fixing the Source
To stop future mould growth, experts repair plumbing leaks, seal cracks in walls or foundations, improve ventilation systems, and recommend installing exhaust fans or dehumidifiers in moisture-prone areas.
3. Air Treatment
Indoor air quality is restored using HEPA air filtration units that capture airborne mould particles, reducing allergen exposure and improving the health of the indoor environment.
4. Prevention Advice
Homeowners receive tailored guidance on maintaining a dry indoor climate from using humidity monitors to scheduling regular checks on roofing, gutters, and basement waterproofing.
What Are the Best Building Materials to Prevent Mould?
The best building materials to prevent mould are mould-resistant plasterboard, anti-mould paint, vinyl flooring, ceramic tiles with waterproof backing, proper sealants, and ventilation systems like exhaust fans.
These materials work by resisting moisture absorption, creating sealed surfaces, and promoting airflow. For example, in bathrooms, laundries, and kitchens, installing waterproof membranes behind tiles and using silicone sealants prevents water from seeping into walls or floors.
In living areas, using treated plasterboard (also called green board) and low-permeability flooring materials like vinyl reduces the risk of hidden dampness. Adding exhaust fans and dehumidifiers further controls indoor humidity, stopping mould before it starts.
Contact Us for Mould Resistant Materials Advice ➔Why DIY Mould Cleaning Doesn’t Work for Big Jobs
DIY mould cleaning doesn’t work for big jobs because household bleach, detergent and sprays can’t penetrate porous materials like plasterboard or timber, hidden mould often goes undetected behind walls or under floors, and cleaning attempts can release airborne mould spores, spreading contamination.
While small surface patches may be manageable, larger infestations or hidden mould require professional mould remediation. Experts use HEPA vacuums, air scrubbers, and antifungal treatments designed for deep cleaning, combined with moisture detection tools and air quality testing to address the root cause, not just the visible mould.
For mould patches larger than a dinner plate or when mould is suspected behind walls, floors, or inside HVAC systems, it’s safer and more cost-effective to call professional services.
- Using bleach on porous materials (it doesn’t penetrate effectively).
- Scrubbing without proper PPE, spreading spores into the air.
- Ignoring hidden sources behind walls or under floors.
What Should I Do If I Find Mould When Renovating or Repairing?
If you find mould while renovating such as under old carpet, inside wall cavities, or near plumbing pipes; stop work immediately to avoid spreading mould spores.
For small areas of mould, visible patches (smaller than a dinner plate), you can wear protective gloves, like rubber gloves and an N95 mask to clean the area with approved mould removal products.
For larger areas, hidden mould, or contamination near HVAC systems, timber framing, or insulation, call professional mould remediation experts like Water Damage Restoration Melbourne. We use HEPA-filtered equipment, moisture detection tools, and air scrubbers to safely remove mould and address the underlying moisture issue.
How to Stop Mould From Coming Back
To stop mould from coming back, eliminate moisture sources and improve airflow in your home:
1. Fix leaks quickly – repair leaks under sinks, around windows, and in the roof to prevent damp patches.
2. Install and use exhaust fans – place in bathrooms, kitchens, and laundries to remove excess humidity.
3. Run a dehumidifier – especially in basements, crawl spaces, or damp rooms to control indoor humidity levels.
4. Opening windows regularly – improve air circulation and reduce trapped moisture inside the house.
5. Schedule regular inspections – after storms, flooding, or if you have an older home with risks like rising damp or foundation cracks.
Can Indoor Plants or House Decor Increase Mould Risk?
Yes, indoor plants, fish tanks, and humidifiers can increase mould risk by raising moisture levels indoors. These items add humidity to rooms, and when combined with poor ventilation or low airflow, they create damp conditions where mould can thrive. Overwatering plant pots, placing wet decor near walls or windows, or using humidifiers without control can lead to condensation, especially on window frames, plasterboard walls, or timber surfaces.
To reduce mould risk, ensure:
- Proper ventilation (use exhaust fans or open windows)
- Moderate watering of indoor plants
- Regular checks for condensation on windows, walls, and around decor
Legal Responsibilities for Mould Issues in Australian Homes
In Australia, both landlords and homeowners have clear legal obligations regarding mould under state and national regulations.
Under the Residential Tenancies Act (varies by state, e.g., Victoria, New South Wales, Queensland), landlords must:
- Provide a safe and habitable property free from health hazards, including mould.
- Maintain the property in good repair, addressing causes like leaking pipes, roof leaks, rising damp, and structural defects.
Tenants are responsible for:
- Taking reasonable steps to ventilate the property, such as using exhaust fans, opening windows, and avoiding activities that increase indoor humidity without airflow.
- Reporting maintenance issues like water leaks promptly.
Tenants are not responsible for underlying building faults that lead to mould, such as cracked foundations, failed waterproofing, or damaged roofs.
Consequences of Ignoring Mould Issues
Ignoring or failing to address mould can result in:
- Formal complaints to regulatory bodies like Consumer Affairs Victoria, NSW Fair Trading, or equivalent state agencies.
- Compensation claims or legal action under tenancy laws for harm, inconvenience, or property damage.
- Public health concerns, especially if the mould spreads to common areas in apartments or multi-unit dwellings.
For homeowners selling a property, the Sale of Land Act (Victoria) and similar legislation require:
- Disclosure of known defects, including mould, water damage, or structural dampness.
- Failure to disclose can trigger contract disputes, price reductions, or even legal penalties.
Conclusion
Mould isn’t just ugly; it’s a sign that something’s wrong in your home. The good news? You don’t have to face it alone.
At Water Damage Restoration Melbourne, we help local families remove mould safely and fix what’s causing it, so you can breathe easy again. From small patches to whole-house problems, we’re here to help.
Worried about mould coming back again and again?
Let our experts find the cause, fix it for good, and make your home safe and healthy.
Book Expert Help ➔Frequently Asked Questions
How do you clean air after mould removal?
After mould removal, professionals clean the air using HEPA air scrubbers and HEPA filters, which capture airborne mould spores and improve indoor air quality. These machines work by filtering out microscopic particles, including mould fragments, dust, and allergens, from the air inside your home. Professionals also check moisture levels, humidity, and ventilation systems (like HVAC ducts and exhaust fans) to ensure the environment stays dry and mould-free in the long term.
How often should I service my HVAC or aircon to prevent mould?
You should service your HVAC system or air conditioner at least once a year to prevent mould growth. Over time, air filters, ductwork, and evaporator coils collect dust, moisture, and organic debris; perfect conditions for mould to develop. Annual maintenance includes cleaning these components, checking for leaks or condensation, and ensuring the ventilation system runs efficiently. This keeps your indoor air clean, reduces humidity, and protects your home from hidden mould problems.
Can new homes or newly built houses get mould?
Yes, new homes and newly built houses can get mould, often due to construction defects or leftover building moisture. Common causes include poor waterproofing, improper ventilation systems, unsealed wall cavities, or wet building materials like timber and plasterboard that weren’t dried properly during construction. Even minor leaks around windows, roofs, or plumbing systems can create damp spots. To prevent mould, ensure early inspections for airflow, moisture control, and proper sealing; no matter how new the home is.
Can mould affect the value of my home when selling?
Yes, mould can reduce your home’s value and make it harder to sell because buyers are concerned about hidden structural damage, health risks, and future repair costs. Unresolved mould problems in walls, ceilings, basements, or HVAC systems can signal water issues like leaks, poor ventilation, or rising damp; all red flags during a home inspection. To protect property value, get professional mould remediation, fix the underlying moisture source, and obtain a clearance certificate or remediation report to show buyers the home is safe and mould-free.
