That black stuff growing around your bathroom window isn’t just ugly—it’s probably telling you something about your house. Most people ignore it, spray some bleach on it, and maybe wipe it down. Then it comes back. Because the real problem isn’t the mould you can see.
Hamilton’s damp climate is rough on houses. Between our wet winters and clay soil that holds moisture like a sponge, properties here face constant moisture challenges. And where there’s moisture, there’s mould. Sometimes visible, often hidden behind walls or under floors, where you won’t spot it until there’s a bigger problem.
Hamilton sits in a bowl surrounded by hills, which traps moisture. We get over 1,100mm of rain each year, and our winters are cold and damp. Add fog, poor ventilation in older homes, and modern homes built too tightly without proper airflow, and suddenly every second house we inspect has some level of mould issue.
A client in Rototuna called us about a funny smell in their eight-year-old home. Our inspector found mould growing inside the cavity behind their feature wall. Water had been getting in through badly installed flashings since the house was built. Eight years of slow water damage, completely hidden until the smell gave it away.
Most people walk through a home during an open inspection and see fresh paint, clean carpets, and tidy gardens. What they don’t see is the history. Has it flooded? Did the previous owners patch up a leak without fixing the actual problem? Are there hidden moisture issues that will become your expensive problem three months after settlement?
Mould issues are one of the most common deal-breakers we find. Our inspectors check moisture levels throughout the property, look for signs of previous water damage, test walls and floors with specialised equipment, and identify conditions where mould is likely growing even if you can’t see it yet.
A proper mould inspection isn’t just someone walking around looking at walls. Our inspectors use thermal imaging cameras that detect temperature differences, indicating moisture behind surfaces. We use moisture metres that measure actual water content in materials.
Roof spaces are a big one. Hamilton’s roof cavities often have poor ventilation. When warm, moist air hits cold roof surfaces in winter, you get condensation. That condensation drips down and soaks into insulation and ceiling linings. We’ve seen homes where the insulation was completely saturated and covered in mould, but the ceiling looked fine from below.
Subfloors are another problem zone. Many Hamilton homes sit on clay soil that expands and contracts with moisture changes. Poor drainage means water can pool under the floor. Add poor subfloor ventilation, and you’ve got a mould farm underneath your feet.
Commercial properties get mould problems too, and the stakes can be higher. A retail space in central Hamilton had black mould growing in the staff bathroom. The landlord thought it was just because the tenants weren’t opening windows. Our inspection found water leaking through the roof into the wall cavity. The mould had spread through the wall into the customer area behind a display unit. The business closed for three weeks while repairs were done.
Office buildings often have mould issues in ceiling spaces and behind wall panels. Modern air-conditioning systems can create condensation problems if they’re not properly maintained. We inspect commercial properties for buyers, tenants, and property managers who need to know exactly what they’re dealing with.
Warehouses present different challenges. Large open spaces with varying temperatures, concrete floors that can sweat, and minimal heating create perfect conditions for mould growth.
Here’s something most people don’t realise—pests love damp, mouldy conditions. Silverfish, cockroaches, and even rodents are attracted to moisture and the organic material that mould grows on. We often find both problems together.
Borer beetles are particularly fond of damp timber. If you’ve got moisture issues leading to mould, chances are you’ve also got conditions that attract timber pests. A client in Flagstaff had what they thought was just a small mould patch. Our inspection found borer in the wall framing, attracted by moisture from a slow leak in the bathroom on the other side of the wall.
Killing mould is pointless if you don’t fix the moisture problem causing it. You can bleach mould off a wall, but it’ll just come back if water keeps getting in. That’s why proper moisture testing matters.
Common moisture sources in Hamilton homes include leaking gutters and downpipes, cracked or missing roof tiles, poorly sealed windows and doors, plumbing leaks in walls or floors, rising damp from ground moisture, and condensation from inadequate ventilation. Each source needs a different fix.
A rental property owner contacted us about mould in a weatherboard villa. The tenant complained about black spots appearing faster than they could clean them. We found moisture coming from three different sources—a leaking gutter, failed window seals, and rising damp because the property had no foundation moisture barrier.
Sometimes, property owners need more than just an inspection report. They need someone to explain what’s happening, why it’s happening, and what their options are for fixing it. We’ve had clients who received insurance assessments that didn’t make sense, quotes from builders that seemed excessive, or disputes with vendors over who should pay for mould remediation.
We explain the inspection findings in plain language, help you understand the scope of work needed, provide realistic timeframes for repairs, and sometimes act as an intermediary between you and contractors or insurance companies. Morgan Kircher, our Managing Director with over 20 years in the industry, has seen just about every type of mould problem Hamilton properties can throw up.
One family discovered mould during renovations. They pulled down one wall and found extensive growth throughout the framing. Their insurance company initially declined the claim, saying it was a maintenance issue. We provided a detailed assessment showing the mould resulted from a building defect—improper waterproofing during original construction. The claim was eventually accepted.
Our inspection reports are detailed but readable. You’ll get photos of every problem area, moisture readings, explanations of what’s causing the issues, and recommendations for fixing them. We don’t do the remediation work ourselves, which means our recommendations are genuinely independent.
The report helps you make informed decisions. If you’re buying, you can negotiate the purchase price. If you own the property, you know what needs fixing and in what order.
Different Hamilton suburbs have different mould risk profiles. Properties near the Waikato River can have higher moisture levels due to groundwater. Older character homes in Frankton and Hamilton West often have poor subfloor ventilation. Newer subdivisions like Rototuna sometimes have mould issues from building defects.
The clay soil across Hamilton is particularly problematic. It holds water during wet periods and cracks during dry spells. This affects foundations and can create pathways for moisture to enter. We’ve inspected homes where ground moisture was wicking up through concrete slabs because no moisture barrier was installed.
If you can see mould, get it checked. But there are other signs. A musty smell that won’t go away often indicates hidden mould growth. Increased allergy symptoms or respiratory issues at home can result from mould spore exposure. Water stains on walls or ceilings mean water has been getting in.
Get an inspection before buying any property. If you’re a landlord, regular inspections help you stay on top of maintenance. If you’re selling, knowing about mould issues before you list means you can address them on your terms.
People sometimes think they’ll just deal with mould problems later. Paint over it, wipe it down, stick a dehumidifier in the room. That approach rarely works. Mould doesn’t just affect surfaces. It grows into materials—into timber framing, into plasterboard, into insulation. Once it’s established in structural elements, surface treatments are useless.
Health impacts are real. Prolonged exposure to mould spores can trigger asthma, cause persistent coughing and throat irritation, lead to chronic sinus problems, and create long-term respiratory issues. Some moulds produce mycotoxins that can cause more serious health problems.
Then there’s property value. A home with known mould problems becomes harder to sell and is worth less money. Buyers are increasingly aware of mould risks and will either walk away or demand significant price reductions.
If you’re concerned about mould in your Hamilton property, get a proper inspection done. It’s not expensive compared to the cost of dealing with undiscovered mould problems.
We inspect properties across Hamilton and the wider Waikato. Our team knows local building types and understands the challenges Hamilton’s climate creates. You get detailed photo documentation, accurate moisture readings, and realistic advice.
Don’t wait until you’re facing a repair bill that could have been avoided. Book a mould inspection and get the facts about your property.
Alert Building Inspection Services provides comprehensive building reports across Hamilton and New Zealand. Trust our expert inspectors to give you clarity and confidence in your property decisions. For professional building inspection services and expert advice, visit our website. You can also read more articles like this on our blog.