Quick answer (BLUF): mould from the 2022 Lismore floods can still be active today inside wall cavities, subfloors and ceiling voids that were never opened during the clean-up, because Category 3 floodwater soaks into timber, insulation and plasterboard and keeps feeding concealed colonies long after surfaces look clean. If your home was inundated in 2022 and you notice musty smells, wall discolouration or respiratory symptoms that ease when you leave the house, arrange a professional assessment with moisture mapping and air sampling; if your home was flooded and has no symptoms but has never been properly assessed, testing first is the sensible move.
The Flood That Changed Everything, and the Mould Problem Nobody Warned You About
On 28 February 2022, the Wilson River peaked at 14.4 metres above sea level in Lismore, the highest flood height ever recorded in the town’s history. More than 10,000 properties were inundated. The scale of destruction was unprecedented for inland northern NSW.
The recovery effort that followed was also extraordinary. Thousands of volunteers descended on Lismore. Government assistance was provided, insurance claims were lodged, and many homeowners undertook heroic clean-up efforts under devastating conditions.
But for thousands of Lismore households, the full extent of the damage was not apparent in the immediate aftermath. Because the most persistent, health-affecting consequence of the 2022 floods was not the mud, the structural damage, or the lost contents.
It was the mould.
This guide is written for Lismore homeowners, those who were flooded in 2022, those who are still dealing with the mould consequences, and those who aren’t sure whether their home’s current condition is flood-related or not.
Why Flood Mould Is Different From Ordinary Mould
Category 3 Water: The Critical Distinction
The floodwater that entered Lismore homes during the 2022 event was not clean water. It was not water from a burst pipe or even from rainfall alone. It was river floodwater, Category 3 contaminated water in the IICRC classification system.
Category 3 water (often called “black water”) is grossly contaminated with:
- Sewage and faecal matter (from overwhelmed septic and sewerage systems)
- Chemical runoff (agricultural chemicals, industrial pollutants, vehicle fluids)
- Biological contamination from the river system
- Debris, sediment, and biological material accumulated upstream
When Category 3 water infiltrates building materials, and it infiltrates deeply, driven by the duration and height of inundation, it does not simply evaporate and leave those materials clean. It introduces a contamination load into the material itself. The mould that establishes in the aftermath of Category 3 water events can include species and contamination conditions not seen in mould from clean water damage.
This is why the IICRC S520 standard requires Category 3 water-affected materials to be treated as contaminated, and why the standard recommends removal rather than in-situ treatment in most cases.
The Concealed Mould Problem
The most important thing to understand about Lismore flood mould is this: what you can see is usually not the full extent of the problem.
When floodwater enters a building, it soaks into porous materials, plasterboard, insulation, timber framing, MDF skirting boards. The water that is absorbed into the paper facing of plasterboard cannot be fully removed by surface drying. The water that soaks into insulation batts cannot be dried out without removing the insulation. The water that saturates timber wall frames does not fully evaporate even after the visible surface appears dry.
These saturated materials, inside the wall cavity, behind the internal lining, above the ceiling, provide the perfect substrate for mould establishment. Permanently dark. Continuously elevated in moisture. Rich in the nutrients (from the organic components of Category 3 water) that feed mould.
Mould in these concealed spaces grows without detection until it either breaks through to the visible surface (typically as a patch or discolouration on the plasterboard face, often appearing first at corners, around skirting boards, or adjacent to power points) or reaches a colony density where MVOCs (microbial volatile organic compounds) permeate through the lining and into the living space as a musty smell.
The Lismore Timeline: Why It’s Not Over
Concealed mould after flooding typically becomes symptomatic:
- 3-6 months post-flood: First musty smell reports, first patches of discolouration on plasterboard surfaces. Often dismissed as residual dampness.
- 6-12 months post-flood: Plasterboard patches become more extensive. Health symptoms (respiratory irritation, headaches, fatigue at home) reported by household members. First professional mould assessments undertaken.
- 12-24 months post-flood: Homes with unaddressed concealed mould show more extensive plasterboard breakthrough. Mould has now had multiple Northern Rivers wet seasons providing additional humidity to sustain growth.
- 24 months+: Chronic mould in unaddressed properties. Some have extensive structural timber involvement. Remediation remains possible and effective but scope is larger.
If your home was flooded in 2022 and it is now 2025 or 2026, you are in the chronic phase. This does not mean remediation isn’t possible. It means it needs to happen.
Update: Where Rebuilt Lismore Homes Stand Now
Several years on, the pattern in Lismore is no longer about the flood itself. It is about the quality of the rebuild. Homes that were stripped to the studs and re-sheeted can still harbour active mould where any of the following happened:
- Framing timbers were not fully dried before re-lining. Moisture content in 90x45 mm hardwood studs can stay elevated for 12 to 24 months. Where lining went back on before readings dropped below 18 to 19 percent, mould has been growing inside the cavity ever since. Slab-on-ground rebuilds have their own version of this: concrete releases moisture into wall base plates for far longer than most people expect, which we cover week by week in our guide to drying out a flooded slab-on-ground home.
- Subfloor debris retained moisture. Flood silt packed under elevated homes holds moisture for months. Where subfloor spaces were not thoroughly cleaned, dried and treated, the underfloor environment stays a reservoir. The same problem inside wall cavities rather than under the floor is covered in our guide to flood mud in wall cavities.
- The rebuild used green or freshly milled timber. Material shortages meant some repair work used unseasoned timber, adding to the moisture load inside the cavity.
- Ventilation was not improved during the rebuild. Many of these homes had inadequate cross-ventilation before the flood. A like-for-like repair simply restores the original problem.
Three groups of rebuilt homes
Fully remediated and holding. Thorough professional remediation before or during the rebuild: cavity strip-out, antimicrobial treatment of framing, post-treatment testing, and adequate drying time before re-lining. These homes are generally performing well, though annual inspection is still worthwhile given the climate and the damage history.
Re-sheeted without full remediation. The pressure to get families back into homes meant some repairs prioritised speed over process. Wall linings went back without cavity treatment, subfloors received surface treatment only, or drying times were compressed. These homes often looked fine in the first year or two and are the group now showing renewed mould activity in the newly lined cavities.
Ongoing active contamination. A smaller but significant group, particularly on the lower-lying streets of North and South Lismore that saw deeper or longer inundation. Some have been through several rounds of surface cleaning without the cavity source ever being addressed. These need full professional remediation, which may mean selective demolition of the new lining to treat the framing behind it.
The pattern is not limited to private homes. Community halls, clubs and other shared-use buildings flooded in 2022 have followed the same trajectory, and carry an added public liability dimension when they reopen to hirers without a documented professional assessment. See our guide on community halls and clubs reopening safely after a flood.
Warning signs in a rebuilt home
| Warning sign | Possible cause | Urgency |
|---|---|---|
| Musty odour returning after a dry spell | Active mould in cavity or subfloor | High |
| New paint bubbling or staining on re-sheeted walls | Moisture migrating from framing | High |
| Household members with worsening respiratory symptoms | Elevated airborne spore counts | High |
| Skirting boards lifting, or wall plaster soft to touch | Persistent moisture in the floor system | Medium to high |
| Visible mould returning within weeks of cleaning | Untreated source still active | High |
| Condensation on windows despite warm weather | High indoor humidity, poor ventilation | Medium |
Two or more of these together point to a professional inspection with thermal imaging and moisture readings, not another round of cleaning products. If your repair work was more recent, our 12-month mould watch plan for flood-recovered homes sets out a monitoring schedule for the first year after repair, when hidden recurrence is most likely to develop.
What the work looks like at this stage
- Comprehensive assessment. A mould inspection and testing at this point should include thermal imaging to find moisture pockets in wall cavities, moisture meter readings at multiple heights on affected walls, air sampling in living areas and inside cavities where accessible, and a visual subfloor inspection.
- Targeted cavity treatment or strip-out. Where readings or imaging indicate wet framing, selective demolition of the re-lining may be necessary. Framing is cleaned, treated with an appropriate antimicrobial, dried to below 15 percent moisture content, and only then re-lined.
- Subfloor treatment. Any elevated home with a flood history should have the subfloor inspected, silt-cleared if that has not been done, and treated. Ventilation improvements, cross-ventilators or mechanical fans, are often warranted in this climate. See our guide on subfloor ventilation for elevated homes.
- Post-remediation air testing. Do not accept clearance on visual inspection alone. Comparison of indoor and outdoor spore counts is the standard way to confirm the remediation actually worked.
How to Know If You Have Concealed Flood Mould
Signs to Look For
Musty smell. A persistent earthy, musty smell, particularly at floor level near flood-affected walls, or in rooms that were significantly inundated, is the most consistent indicator of active concealed mould.
Plasterboard discolouration. Dark staining, greyish patches, or brownish-yellow stains that appear on internal walls, typically:
- Near floor level on walls that were submerged
- At corners where two flood-affected walls meet
- Around power points and light switches (where the wall lining has penetrations)
- Along the base of plasterboard where it meets skirting boards
Soft or hollow plasterboard. Tap the wall surface. A dull, soft sound (rather than the normal hollow tap) indicates the plasterboard is wet or delaminated inside, a strong sign of concealed moisture and mould.
Elevated moisture readings. A moisture meter reading on the surface of internal walls affected by flooding will typically show elevated readings even when the surface appears dry, if there is moisture still trapped in the wall cavity.
Household health symptoms. Respiratory irritation, frequent coughing or sneezing, eye or throat irritation, persistent headaches, or fatigue that is worse at home and improves when away, particularly in household members who spend the most time in flood-affected rooms.
Professional Investigation Methods
Visual inspection alone is not sufficient for identifying concealed flood mould. The methods we use:
Thermal imaging. Temperature differentials on wall surfaces can indicate moisture pockets inside wall cavities, cooler areas where evaporating moisture is drawing heat from the wall face. Thermal imaging can identify moisture without any invasive investigation.
Calibrated moisture mapping. Systematic moisture meter readings across all wall surfaces affected by flooding, at multiple heights. Patterns of elevated moisture readings indicate areas where wall cavity investigation is warranted.
Air sampling. Laboratory analysis of air samples from within flood-affected rooms can identify elevated mould spore concentrations even before visible mould is present. This provides objective evidence of active mould colonisation.
Borescope investigation. Small-diameter cameras inserted through minimal penetrations in the wall lining allow visual inspection of the wall cavity without full demolition. The most direct method for confirming whether mould is present in the cavity.
Testing vs Remediating: When to Do Each
This is the most common question we receive from Lismore homeowners.
Test First If:
- You have a strong suspicion of flood mould but no definitive visual evidence
- You need objective documentation for an insurance claim or recovery assistance application
- You want to establish a baseline before deciding on remediation approach
- The household includes members with respiratory conditions who need to know whether occupancy is safe
Remediate Without Delay If:
- You have visible mould breakthrough on walls that were flooded
- A persistent musty smell has been present for more than a few weeks
- Household members are experiencing health symptoms consistent with mould exposure
- Moisture readings on flood-affected walls are significantly elevated
- You can see soft or delaminating plasterboard on flood-affected walls
Test AND Remediate If:
- You need insurance documentation that covers both the pre-remediation extent and the post-remediation clearance
- A comprehensive paper trail is required for legal, insurance, or recovery purposes
Insurance Claims for Lismore Flood Mould
Many Lismore homeowners have faced significant difficulty with insurance claims for flood mould, particularly where:
- The initial claim was settled without accounting for concealed mould that presented later
- The insurer disputes the connection between the flood event and the current mould condition
- The policy excludes mould as a standalone condition
Several things help:
Professional documentation of the causal link. An inspection report that establishes the connection between the 2022 flood event and the current mould condition, based on the location of mould (walls flooded in 2022), moisture patterns consistent with inundation history, and the building’s flood record, is the most important piece of documentation for a flood mould claim.
Pre-remediation assessment. Do not undertake any remediation before documenting the current condition in a professional report. Insurers need to see what was there before remediation to assess the claim.
IICRC-standard remediation scope. An insurer assessing a mould remediation claim needs a scope of works that follows IICRC S520 protocol. Our scopes are written to meet this standard.
The contractor provides documentation in the format required by major insurers and can liaise with loss adjusters on your behalf. Contact us to discuss your specific situation.
What Proper Flood Mould Remediation Involves
Post-flood mould remediation in Lismore homes generally follows this process:
- Pre-remediation assessment, inspection, moisture mapping, air sampling, photographic documentation, scope of works
- Containment, sealing off affected areas to prevent cross-contamination during remediation
- Material removal, removing mould-affected plasterboard, insulation, and skirting boards
- Structural drying assessment, checking that timber frames are dry enough for treatment and rebuilding
- Antimicrobial treatment, application of commercial-grade antimicrobials to structural timber, ceiling framing, and all surfaces within the containment zone
- HEPA vacuuming, removing residual spores from the treated area
- Clearance testing, air sampling post-remediation to confirm mould levels have returned to baseline
- Documentation, completion report for insurance purposes
Frequently Asked Questions
My Lismore home was flooded in 2022 but I’ve been living in it since. Is it safe? This is not a question we can answer remotely. If your home shows signs of concealed flood mould, musty smell, plasterboard discolouration, elevated moisture readings, then occupying it while the mould remains unaddressed means ongoing exposure to elevated mould spore and MVOC levels. The health significance depends on the individuals in the household, the severity of the mould, and the ventilation of the home. A professional assessment will give you objective information to make that decision with.
I had my walls cleaned after the flood. How do I know if the mould is gone? If the cleaning addressed only the visible surface and did not involve professional investigation of wall cavity conditions, moisture mapping, and post-treatment air sampling, the answer is that you can’t know without additional assessment. Surface cleaning of flood-affected walls that were not also moisture-mapped and professionally dried does not reliably address concealed mould in the cavity. A post-treatment air sampling test is the only objective way to confirm clearance.
Are there any current government programs that help with flood mould in Lismore? Recovery assistance programmes have changed significantly since 2022. We recommend contacting NSW Reconstruction Authority directly for current programme information. The contractor can provide the documentation required for most recovery assistance applications.
Should I move out while mould remediation happens? For major structural remediation involving containment and HEPA filtration equipment, yes, occupants should not be present during active work, particularly children, elderly, and anyone with respiratory or immune conditions. We will advise on the specific requirements for your job.
Getting Help
If your Lismore home was flooded in 2022 and you have not had a comprehensive professional mould assessment, or if you have had an assessment and the mould was not fully addressed, contact us for a free consultation.
We flag Lismore enquiries as priority, we know the 2022 flood context, and the contractor provides the documentation that insurance claims and recovery assistance applications require.