How to Test a House for Mould

Want to know if your home has mould? Collect air or surface samples from suspect areas and have them analysed, either with a quality DIY kit or by a certified inspector who can also check hidden spots.

Mould can damage your health, weaken building materials, and spoil indoor air. Whether it’s toxic Stachybotrys or common Cladosporium, early detection is key. Modern methods like air sampling, surface swabs, and qPCR testing can uncover spores without tearing into walls.

Think of it as a quick health check for your home fast, accurate, and the easiest way to decide if you need simple cleanup or full remediation.

Why Test for Mould in Your Home

You wouldn’t ignore a strange noise in your car engine, so why overlook signs of mould? Left unchecked, mould spores can:

• Trigger respiratory symptoms, allergies, and asthma flare-ups.

• Compromise indoor air quality through airborne mycotoxins.

• Damage timber, drywall, insulation, and other building materials.

• Indicate hidden water leaks or chronic dampness.

Testing will give you peace of mind. Even if you can’t see mould, it could be thriving behind plasterboard, under carpets, or in ventilation ducts. A proper test tells you:

• If mould is present

• What type of mould is it

• How severe the contamination might be

That information guides whether you can handle the cleanup yourself or need professional remediation.

Warning Signs of a Mould Problem

Not sure whether it’s worth testing? Mould often hides in plain sight—or just out of view—so recognising the early warning signs is essential. Here’s what to watch for before the problem spreads.

Visible spots or staining on walls, ceilings, and floors

A change in surface colour can be your first clue.

• Black, green, or brown blotches aren’t just dirt—they may be active mould colonies or dried spores waiting for moisture to reactivate.

• Discolouration in symmetrical patterns can also indicate water intrusion feeding fungal growth.

Persistent musty odours

When your nose notices what your eyes can’t, pay attention.

• That damp, earthy smell is often caused by microbial volatile organic compounds (mVOCs) released during mould metabolism.

• If the smell lingers despite cleaning, it’s a strong sign spores are hidden nearby.

Damp patches, condensation, or signs of water damage

Moisture problems create the perfect breeding ground for spores.

• Leaks, rising damp, or poor insulation can fuel mould growth.

• Look for bubbling paint, warped skirting boards, or peeling wallpaper as visual cues.

Hidden Risk Areas

Sometimes the worst mould problems are in places you rarely check.

• Enclosed spaces with limited airflow and past water ingress are prime candidates for mould growth.

• Don’t forget HVAC systems—air handlers can spread spores throughout the home.

Mould Testing Options

Not all mould tests are created equal—some are like a quick selfie, others like a full medical scan. The right choice depends on how urgent your situation is, your budget, and whether you want a simple “yes/no” answer or a full contamination profile.

DIY Kits and Their Limitations

If you want a quick, low-cost snapshot, DIY mould kits can give you a starting point.

• These usually involve petri dishes or adhesive slides to capture airborne spores over a set time.

• They’re useful for peace of mind or as a first check before calling in a professional.

• The drawback? Most can’t tell you the mould species, the spore concentration, or the precise source of contamination—meaning you may still need professional testing to confirm results.

Professional Inspections for Full-House Assessment

When accuracy matters, a trained inspector is your best option. Certified mould specialists bring experience, calibrated instruments, and investigative skills that go beyond simply detecting spores.They identify moisture sources, assess the spread, and provide targeted remediation advice.

Common Testing Methods

Depending on your home’s layout and the suspected problem, different testing methods may be used:

• Air quality sampling: Compares indoor airborne spore counts to outdoor levels, revealing hidden mould growth even if no patches are visible.

• Surface swabs: Collects spores or active colonies from building materials, furniture, or fixtures to confirm contamination.

• VOC/mVOC detection: Detects gases emitted by mould during growth, useful for odour-heavy but visually clean environments.

• qPCR lab analysis: A DNA-based method that precisely identifies mould species and quantifies their presence—ideal for detailed health risk assessment.

How to Carry Out a Mould Test

If you’re ready to check your home, following the correct process will give you accurate, actionable results—whether you’re using a DIY kit or hiring a professional.

Identify and Prioritise Areas for Testing

Start with locations most likely to harbour mould.

• Focus on rooms with a history of leaks, condensation, or persistent musty odours.

• Don’t overlook high-risk zones such as attics, crawl spaces, and cold exterior walls where moisture can linger unnoticed.

Select the Most Suitable Test Method

Choose the method that matches your suspected problem.

• Air sampling works best for detecting hidden mould growth.

• Surface swabs are ideal for confirming visible mould patches.

• VOC/mVOC detection helps pinpoint odour-related issues without obvious visual signs.

Collect Samples Following Best Practices

Proper sampling is critical for reliable results.

• Wear gloves and a mask to avoid inhaling spores or contaminating samples.

• Use sterile equipment and follow the kit or inspector’s instructions exactly.

Send to a Certified Lab (if Required)

Lab analysis provides detailed insight into what you’re dealing with.

• Laboratories can identify mould species, measure spore concentrations, and assess potential health risks.

Receive and Review the Results

Understand the findings before deciding your next move.

• Compare indoor results with outdoor baselines to determine if levels are elevated.

• Use the data to guide whether you need simple cleaning or full professional remediation.

Interpreting Mould Test Results

A lab report can feel like alphabet soup—Penicillium here, Aspergillus there, numbers everywhere. Here’s how to decode it:

• Understanding mould species and spore levels

  • Not all mould is equally harmful. Some common household species are more of a nuisance than a danger, while others (like certain strains of Stachybotrys) produce potent mycotoxins.

• Identifying harmful vs. low-risk mould types

  • High counts of allergenic or toxigenic moulds should prompt immediate action. Low-level, common environmental spores may not require urgent remediation.

• Determining the urgency of action based on findings

  • Results will often indicate spore concentration in spores per cubic meter (sp/m³). Extremely high readings or dangerous species suggest urgent removal and moisture control.

Think of it as reading blood test results for your home—numbers alone mean little without context, but in the right hands, they can guide an effective recovery plan.

What to Do if Mould is Detected

A positive mould test isn’t the end of the story—it’s the start of your clean-up and prevention strategy. Acting quickly will protect your health and prevent further property damage.

When to Use Professional Remediation Services

Not all mould problems can be solved with DIY cleaning.

• If mould is widespread, embedded deep in materials, or identified as high-risk types like Stachybotrys (black mould) or certain Aspergillus species, bring in licensed remediators.

• Professionals follow strict containment, removal, and disposal procedures to prevent spores from spreading to unaffected areas.

Fixing Underlying Moisture or Ventilation Problems

Removing mould without addressing the cause means it will likely return.

• This could mean repairing roof flashing, resealing windows, improving drainage, or upgrading bathroom and kitchen ventilation.

• In some cases, adjusting the home’s grading or adding vapour barriers can help keep moisture out.

Confirming Removal with Follow-Up Testing

Always verify that remediation has worked.

• Post-remediation verification (PRV) tests confirm that spore counts have returned to safe, normal levels.

• This step ensures there’s no secondary contamination or lingering hotspots.

Preventing Future Mould Issues

Preventive measures cost far less than dealing with recurring mould outbreaks. Think of it as mould-proofing your property for the long term.

Moisture Control Strategies

Stop mould at its source—water.

• Maintain indoor humidity below 60% with dehumidifiers in basements, laundry rooms, and other damp-prone spaces.

• Fix even small leaks immediately to prevent hidden water damage.

Ventilation Improvements

Good airflow keeps moisture from settling.

• Keep enclosed spaces like lofts, crawl spaces, and wardrobes ventilated.

• Install or upgrade extractor fans in wet rooms, and consider timed fans that continue running after use.

Routine Inspections and Maintenance Tips

A little vigilance goes a long way.

• Include mould checks in your seasonal home maintenance routine.

• Monitor any recurring damp areas or changes in indoor air quality—they may be early warning signs of a new issue.

Finding a Trusted Testing Service

Choosing the right mould testing professional can make the difference between a quick fix and an ongoing problem. A good inspector won’t just take samples—they’ll provide a clear action plan based on accurate results.

What to Look For

Before hiring, check that the service meets these essential standards:

• Qualifications: Look for certification or membership with reputable organisations such as the Indoor Air Quality Association (IAQA) or the American Council for Accredited Certification (ACAC). These credentials show the inspector follows recognised industry practices.

• Method Range: The ability to perform air, surface, and advanced molecular tests ensures they can adapt their approach to your specific situation.

• Reporting Clarity: The report should explain results in plain language, highlight any urgent issues, and suggest next steps—not just present raw numbers.

Smart Hiring Tips

Protect yourself from unnecessary costs and conflicts of interest by following these steps:

• Get Multiple Quotes: Comparing at least two or three services gives you a better sense of fair pricing and service scope.

• Ask for a Sample Report: This shows how detailed and clear their findings will be before you commit.

• Separate Testing from Remediation: To avoid bias, it’s often best to hire one company for testing and another for removal.

A trustworthy testing service leaves you informed, confident, and ready to take the right action—not more confused about what to do next.

Conclusion

With the right testing, whether it’s a quick DIY check or a professional assessment, you can detect issues early, take targeted action, and protect both your health and your property.

At Ex10, we provide thorough, accurate mould inspections using advanced testing methods to identify and address problems at the source. Our expert team gives you clear results, actionable solutions, and peace of mind.

Call us today on 01202 618240 to book your inspection and keep your home safe and healthy.

Frequently Asked Questions

How can I tell if my house has mould without seeing it?

Mould can grow in hidden areas long before it becomes visible. Warning signs include persistent musty odours, damp spots, unexplained allergy or asthma symptoms, and evidence of past water leaks. Professional tests—such as air sampling, surface swabs, or mVOC detection—can confirm the presence of hidden mould colonies.

Are DIY mould test kits accurate enough?

DIY kits can give you a basic yes/no answer, making them useful for an initial check. However, they rarely identify mould species, quantify spore levels, or pinpoint the contamination source. For detailed results and an action plan, professional testing is far more reliable.

What’s the best method for testing mould in a home?

The best method depends on the situation. Air sampling is ideal for detecting hidden growth, surface swabs work well for visible patches, and VOC/mVOC detection helps when there’s an odour but no obvious mould. qPCR lab analysis offers the most precise identification and spore count.

How much does professional mould testing cost?

Most professional mould inspections range from $200–$600. Costs vary depending on the size of the home, number of samples, and whether advanced techniques—such as DNA analysis—are used. Some companies include follow-up testing in their pricing.

What should I do if my mould test comes back positive?

Address the moisture problem first, whether it’s a leak, poor ventilation, or rising damp. Remove or professionally clean contaminated materials to prevent spore spread. Always retest after remediation to ensure the mould has been fully eliminated.