What to Do After Discovering Mould — Step-by-Step Australia Guide

Discovering mould in your home is alarming, but the instinct to clean it immediately can make the situation significantly worse. The first steps are about assessing — not acting.

• Do not disturb the mould before documenting. Any disturbance — brushing, wiping, even walking past — releases spores into the air. Photograph the affected area first. Include a scale reference (a coin, ruler, or your hand) so the area can be assessed from the photograph.
• Photograph with good lighting. Use a torch or additional lighting if necessary. Capture the full extent of visible mould, any discolouration on adjacent materials, and any visible water damage or moisture staining near the affected area.
• Smell test — musty odour without visible mould. A persistent musty or earthy odour in a room, even without visible mould, is a strong indicator that mould is present inside wall cavities, under flooring, or behind cabinetry. Mould hidden inside structures is often more extensive than surface mould.
• Check the moisture source before anything else. Mould cannot grow without a moisture source. If you treat the mould without fixing the moisture source, mould will return. Look for water staining, peeling paint, condensation, or damp patches near the affected area to identify the cause.

Not all mould requires professional remediation. The decision depends on the area, the surface type, and whether the moisture source has been fixed.

• DIY may be appropriate when all of the following apply: The surface is hard and non-porous (tiles, glass, painted metal), the affected area is less than 0.1 square metres, the growth is isolated with no spread to adjacent materials, and the moisture source has already been identified and fixed. Use a HEPA vacuum followed by an antimicrobial product rated for mould, and wear an N95 mask, gloves, and eye protection.
• Call a professional when any of the following apply: The affected area is larger than 0.1 square metres, the mould is on porous materials such as plasterboard, timber, insulation, or carpet, the mould is inside HVAC ducting or air conditioning systems, the mould followed a flood event or water damage incident, there is structural mould inside wall or ceiling cavities, or if any occupant is experiencing health symptoms consistent with mould exposure.

When in doubt, a professional mould assessment is a low-cost way to determine the scope and whether DIY is safe. NRPG contractors can assess and advise before any work is committed.

Mould remediation without fixing the moisture source is temporary at best. The underlying cause must be identified and repaired before any remediation begins — or the mould will return within weeks.

• Common moisture sources in Australian homes:
• Roof leaks. The most common cause of mould in ceiling cavities and upper wall areas. Often seasonal — mould appears after rain events and is mistaken for condensation.
• Condensation. Common in poorly ventilated rooms and in Australian homes with air conditioning that creates large temperature differentials. Typically presents on external walls, around windows, and in bathrooms.
• Rising damp. Moisture wicking up from the ground through masonry or concrete slab. Presents as mould and staining on lower wall areas, often with a distinct tide mark. Common in older homes without effective damp courses.
• Plumbing leaks. Slow leaks from supply pipes or drain pipes inside walls are often undetected for months. Look for unexplained increases in water bills, damp patches on walls, or soft spots on flooring as indicators.
• A professional leak detection service can identify hidden moisture sources using thermal imaging and moisture meters before demolition of wall or ceiling linings.

Mould insurance claims succeed or fail based on how well the causal chain is documented. Understanding the coverage boundary and the evidence requirements is essential.

• Covered mould vs non-covered mould. Mould arising from a covered event — such as a storm, burst pipe, cyclone, or appliance failure — is generally covered as a secondary damage item. Mould from gradual moisture buildup over time, condensation, or lack of maintenance is typically excluded. Your Policy Disclosure Statement (PDS) will specify the exact exclusions.
• Causal chain documentation. You must be able to demonstrate that the mould grew as a direct result of the covered event. This means documenting the event, the water ingress pathway, the affected materials, and the timeframe from event to mould discovery. NRPG contractors prepare this documentation as part of the remediation scope.
• Photograph evidence before any cleaning. Once cleaning or remediation begins, the original extent of mould is no longer visible. All mould must be photographed in its original state — including areas that will be opened up (wall linings, flooring) — before any work commences.
• IICRC S520 scope requirement for insurer sign-off. Most insurers require that mould remediation is performed to IICRC S520 standard and that the contractor provides an S520-compliant scope of works and completion certificate. This is the standard required for insurer sign-off. Ensure your contractor can provide this documentation before engaging them.