In Australia, the scale of the problem is bigger than many realise. According to the WA Department of Health, it’s estimated that up to one-third to half of homes in Australia are affected by indoor mould. The health risks are real, too. Housing-related issues such as damp and mould are believed to contribute significantly to poor health outcomes, particularly in relation to respiratory and cardiovascular conditions, as highlighted by research from the University of Melbourne.

Spotting mould on your ceiling or bathroom wall is never a good feeling — but knowing who to call about it can be just as confusing as the mould itself.

While many people jump straight to cleaning the mould from surfaces, mould is often a symptom of something deeper: a hidden leak, poor airflow, failed insulation, or even rising damp. That’s why treating mould without tackling the root cause usually leads to it coming straight back.

A lot of us are wondering who to call for help in these matters. Many homeowners aren’t sure which type of professional to engage — especially when the source of the problem could be tucked away in a roof cavity or under the floorboards.

This blog will help you take that next step. We’ll guide you through which type of expert to call — and when — so you can get to the bottom of the issue with confidence.

Why finding the source of mould matters

When you find mould in your home, it’s tempting to just reach for a spray and scrub it away. And while surface cleaning might make things look better temporarily, it rarely solves the real problem — because mould isn’t just a cosmetic issue. It’s a sign that something in your home’s structure, airflow, or moisture management isn’t working as it should.

Mould thrives in damp, poorly ventilated spaces — and that excess moisture has to come from somewhere. It might be a slow plumbing leak inside a wall, steam from an unvented bathroom, water seeping in through a cracked roof tile, or even rising damp from under the floor. If you don’t identify and resolve the underlying issue, mould will almost always return.

That’s why finding the source is so important.

Cleaning without fixing is like mopping up water without turning off the tap.

On top of that, hidden mould and moisture problems can silently impact your home’s structure and your health. Mould spores can worsen respiratory conditions like asthma or allergies, and persistent dampness can damage walls, ceilings, insulation, and flooring — leading to expensive repairs down the track.

By investigating the source early on, you not only avoid the cycle of reappearing mould, but you also save yourself a lot of stress, time, and money. And just as importantly, you create a healthier, safer living environment for everyone in your home.

Common areas mould appears and who to call

Mould has a sneaky way of showing up in places you might not expect—on your bathroom ceiling, along a bedroom wall, or even inside cupboards. And depending on where it turns up, the cause (and the person you need to call) can be very different.

Here’s a breakdown of some of the most common mould-prone areas in the home, what might be causing the issue, and the type of professional best suited to help you investigate and fix it.

 

Keep in mind that sometimes mould in one spot can be the result of issues elsewhere. For example, mould on a ceiling could be caused by an exhaust fan that vents into the roof cavity rather than outside—or it could be a cracked tile letting in rainwater. That’s why it’s helpful to get a professional involved who knows what signs to look for.

In the next section, we’ll cover what to do when you’re not quite sure where the problem is coming from.

Don’t know the cause? Here’s who to call first

Sometimes mould just... appears. Maybe it’s creeping along a ceiling corner or showing up behind furniture, but you’re not sure why. There’s no obvious leak, no recent storm damage, and your plumbing seems fine. So, where do you even begin?

If you’re scratching your head trying to figure out what’s causing the mould, the best place to start is with someone who can take a step back and look at the bigger picture—someone trained to identify hidden moisture problems, ventilation issues, or building faults.

✅ Start with a Building Inspector or Building Biologist

These professionals are trained to assess the structure of your home and uncover what might be going on behind the scenes. They’ll look for things like:

• Leaks behind walls or under floors
  

• Poor insulation causing condensation
  

• Exhaust fans venting into roof cavities
  

• Gaps in waterproofing or flashing
  

• High humidity hotspots

Some use thermal imaging, moisture meters, or even borescopes (tiny cameras) to detect damp areas that aren’t visible to the naked eye.

If you’re in a newer home or rental and suspect building design may be part of the issue, a building biologist may also assess things like airflow, material choices, and indoor air quality.

You can find certified Building Biologists at the Australasian Society of Building Biologists here. 

You can hire a licensed Building Inspector anywhere in Australia—just be sure to describe the mould issue clearly when making an enquiry. Let them know where you’ve noticed the problem, how long it’s been there, and whether it seems to reappear after certain events (like rain or showers). And don’t forget to ask for a quotation upfront so you know what’s included in the inspection.

✅ Or call a Mould Assessor or Environmental Hygienist

If you're particularly concerned about health effects—or if the mould keeps coming back despite regular cleaning—this is another excellent option. A qualified mould assessor can:

• Measure airborne mould spore levels
  

• Identify the type of mould present
  

• Track moisture problems to their source
  

• Provide a full report (helpful if you’re a renter or dealing with insurance)

Their goal is to help you understand what’s feeding the mould and how to stop it from returning—not just remove what you can see.

If you’re not sure where to start, you can find more information and a list of organisations and laboratories in Australia that provide mould inspection services through Toxic Mould Support Australia.

🔍 Tip: Ask specifically for a building moisture inspection or an indoor mould assessment—these terms let them know you need a detailed diagnostic, not just a visual check.

When you need a specific expert

Once you've identified what’s likely causing the mould—or a general inspection has pointed you in the right direction—it’s time to bring in a specialist who can address the root of the problem directly.

Here’s a rundown of the most common types of mould-related issues and the professionals who are best equipped to deal with them:

1. Plumber

If your mould problem is traced back to a leaking pipe, water seeping from under a shower recess, or damp patches behind walls or cabinetry, a licensed plumber is your go-to. They can:

• Locate and repair hidden leaks
  

• Reseal showers and wet areas
  

• Check for issues with drainage or water pressure

2. Roofer

Mould on ceilings, especially near cornices or around light fittings, could mean water is getting in from above. This is where a roofing specialist comes in. They can:

• Inspect and repair roof tiles, flashing, and valleys
  

• Identify leaks or weak points in roof sheeting
  

• Ensure proper water runoff

3. Ventilation Specialist

Condensation-related mould—like what you often see in bathrooms or on cold surfaces—can signal poor airflow or improperly installed exhaust fans. They can:

• Install or upgrade exhaust systems
  

• Redirect vents that are dumping moist air into roof spaces
  

• Improve airflow in problem areas

4. Damp Specialist

If the issue is moisture rising from the ground or seeping through foundations, especially in older homes or properties with poor subfloor ventilation, a damp expert is key. They can:

• Treat rising damp
  

• Improve drainage and underfloor airflow
  

• Apply barriers or coatings to prevent further moisture ingress

5. Insulation or Energy Assessor

In homes where condensation keeps forming despite fixing leaks and airflow, thermal bridging or poor insulation might be to blame. These assessors can:

• Identify cold spots that cause moisture to form
  

• Recommend insulation improvements or window glazing upgrades
  

• Help balance indoor temperature and humidity

6. Air Conditioning Cleaning Technician (HVAC Mould Specialist)

If you notice musty smells when your air con is running or see visible mould around vents, there’s a good chance the issue is coming from inside the system.

These technicians can:

• Clean internal components like coils, filters, and ducts
  

• Remove mould build-up from split system units or ducted vents
  

• Ensure moisture isn’t accumulating inside the system
  

• Recommend maintenance schedules to keep it mould-free

Look for companies that offer air conditioner sanitising or HVAC mould cleaning—some specialise specifically in this service, especially in humid or tropical regions where moisture build-up is more common.

Read related article: Is Your Air Conditioner Harbouring Mould? Here's How to Find Out

Bringing in the right expert for the job not only solves the current problem but also helps prevent mould from returning. And the sooner you act, the more manageable the fix is likely to be.

Want to test for mould yourself first?

If you're not quite ready to call in a professional—or you're just curious about what's growing—you can start by doing a simple DIY mould test at home.

The SAN-AIR™ Mould & Bacteria Test Kit is an easy, non-invasive way to collect air, water, or surface samples to see whether mould is present in your environment. It’s especially handy if you suspect something’s off (like a musty smell or unexplained health symptoms), or when there’s a suspicious black patch forming near the windows or walls.

If you’d like to go a step further and identify exactly what type of mould you’re dealing with, you can even send your sample to a specialist lab for analysis. In Australia, some of the labs that accept samples from DIY kits include:

• Mycolab / Mycotec

• Eurofins Environment Testing

They can provide you with detailed insights about the species present and whether they may pose a health risk—information that can be useful when speaking with mould professionals or arranging remediation.

DIY testing won’t replace a full inspection, but it’s a valuable first step if you’re unsure or want evidence before proceeding.

Shop SAN-AIR™ Mould & Bacteria Test Kit at Aussie Pharma Direct.

Extra tips before you call the professionals

Before you jump on the phone with a professional, there are a few things you can do to help make the inspection smoother—and possibly save time and money in the process. A little bit of observation can go a long way in helping the right expert identify the root cause.

Here are some helpful tips to keep in mind:

1. Take clear photos of the mould

Document where it’s showing up, how big the patch is, and whether it’s spreading. Take note of colour, texture, and any signs of water damage nearby (like bubbling paint or stains). If it comes and goes, try to capture it at its worst.

2. Look for patterns

• Does the mould return after heavy rain?
  

• Is it worse after showers or cooking?
  

• Does it only show up in winter or when the room is closed up?

These details can help point to whether the issue is related to plumbing, roofing, condensation, or ventilation.

3. Check nearby moisture sources

Is the mould near a bathroom, kitchen, laundry, or air conditioner? Look for signs of leaks, steamy windows, or damp smells. Sometimes simply knowing what’s behind a wall (like plumbing) can give your inspector an early clue.

4. Prepare some notes before you call

When contacting a building inspector, plumber, or mould assessor, describe:

• Where the mould is appearing
  

• How long it’s been there
  

• Whether it’s reappeared after cleaning
  

• Any renovations or repairs that happened recently
  

• Any signs of water ingress (like ceiling stains or wet carpet)

The more information you give, the easier it’ll be for them to understand the issue and quote accordingly.

5. Ask the right questions

When you make contact:

• Ask if they offer a moisture or mould investigation (not just a quick fix)
  

• Request a quotation in writing
  

• Confirm if a report will be provided (especially useful for renters or insurance claims)
  

• Check what’s included in the service—some may offer thermal imaging or air sampling, while others focus only on repairs

Coming prepared not only helps the professional get to the source faster, but also ensures you’re getting the right service for your situation.

Conclusion: Solving the mould problem starts with the right help

Finding mould in your home can feel overwhelming—but the good news is, you don’t have to figure it out alone.

The key is not just to clean what you can see, but to identify and fix the root cause. That might mean calling in a building inspector for a broad assessment, a plumber to check for leaks, or a mould assessor to investigate air quality and spore levels. And if you don’t know where to start, professionals like building inspectors or mould specialists can help point you in the right direction.

Being proactive now can save you from ongoing damage, health risks, and repeated clean-ups later on.

While you're investigating and resolving the source, using safe and natural mould control products can help keep things under control in the short term. If you're looking for options to help manage mould in the meantime, browse our mould prevention range by SAN-AIR here.

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Allergies Asthma Management Health & Wellbeing Home & Lifestyle Mould Removal Mould Solutions Respiratory Health Safety & Protection Tips Winter