The short answer
Not always. If you can see mould and you know why it is there, testing adds little — the job is to fix the moisture. Testing earns its cost when mould is suspected but hidden, when you are not sure a mark is mould, or when someone else needs documented results: a buyer, an insurer, a landlord or a tribunal.
What the health authorities actually say
The World Health Organization’s 2009 guidelines on dampness and mould concluded that no quantitative health-based guideline values or thresholds could be recommended for mould in indoor air. Its central recommendation is simpler: persistent dampness and microbial growth indoors should be avoided or minimised.
The Australian Centre for Disease Control’s advice is similar in spirit — mould needs moisture, so keep spaces ventilated and dry and fix leaks, plumbing faults and roof problems. Neither tells you to count spores before acting.
That matters, because it means a test is a tool for answering a specific question, not a box to tick.
When testing is worth it
- You can smell it but can’t see it. A musty smell with no visible growth often means mould in a cavity, under flooring or in the subfloor. Air sampling compared with outdoor air, plus moisture mapping, can show whether there is a hidden source.
- You’re not sure it’s mould. Dark marks can be soot, dust tracking, tannin bleed from timber or mould. A tape lift settles it.
- Somebody else needs evidence. Buyers before settlement, owners making an insurance claim, tenants and landlords disagreeing about cause, and anyone signing off works need documented, dated results.
- After a flood or leak. Materials stay wet long after the surface dries. Moisture mapping shows what still needs drying before walls are closed up.
- After works. An independent clearance check confirms the area is dry and spore levels are back to background.
When it probably isn’t
- A patch of mould on bathroom grout or silicone in a room with a weak exhaust fan.
- Mould on a wall behind a wardrobe pushed hard against an external wall, with no sign of a leak.
- A one-off after an unusually wet week that does not come back once the house is aired.
In those cases the Queensland Government’s mould and damp advice — keep the home dry and aired, leave a gap behind furniture, wipe away moisture — is the place to start. If the mould keeps returning, that is the point to get an inspection, because recurring mould usually means a leak or building problem.
What a test can’t do
No test can tell you whether a building caused a particular person’s symptoms. That is a medical question for a GP. A mould inspection describes the building — where it is damp, why, and what is growing — so the decision about the building can be made on evidence.
Questions people ask
Can I just treat visible mould myself?
For a small patch on a hard surface with an obvious cause, many people do. Queensland Health advises protective gear and not dry-brushing, which spreads spores. If it keeps returning, look for a leak or building problem.
What does a test tell me that my eyes can't?
Whether there is hidden growth adding spores to the air, whether a stain is mould at all, and how far damp has spread inside walls and floors.
References
- [1]WHO guidelines for indoor air quality: dampness and mould (2009) — World Health Organization Regional Office for Europe
- [2]Preventing mould exposure — Australian Centre for Disease Control
- [3]Mould and damp — Queensland Government
Checked against these references on 2 November 2026.