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Maroubra Apartment Aircon Leak: Ceiling Mould Strip-Out & HEPA Cleaning Case Study
By Michael Nguyen | Indoor Environmental Professional (IEP) | IICRC WRT, AMRT, ASD (69486970) | Mould Testing Technician (NAT10913005) | Licensed Builder NSW 392154C (Supervisor, KBL+RENO)
Quick answer: An air conditioner drip tray leaked into the ceiling of an apartment unit in Maroubra, and mould was visible inside the ceiling hatch. We set up containment, stripped out the water-damaged plaster, then HEPA vacuumed every surface with slow, overlapping passes. An independent building biologist will carry out the clearance test (post-remediation verification).
Aircon drip trays catch the water that the indoor unit pulls out of the air. When the drain line blocks, the tray cracks or the unit sits out of level, that water spills into the ceiling below. Because it happens slowly and out of sight, the plaster can stay wet for weeks before anyone sees a stain or a sag.
The Job
On 13 November 2026 we started work on an apartment unit in Maroubra, in Sydney's Eastern Suburbs. Water from the air conditioner drip tray had leaked into the ceiling and damaged the plaster, and mould could be seen inside the ceiling hatch. In an apartment, a leak like this can also affect the unit below or common property, so the strata manager may need to be kept informed. The plan:
Set up containment so dust and debris stay in the work area
Strip out the water-damaged ceiling plaster
HEPA vacuum all exposed surfaces in the room
Independent clearance testing (PRV) before any rebuilding
Why an Aircon Leak Leads to Ceiling Mould
Plasterboard soaks up water quickly. Once wet, it loses strength, stains and can sag or collapse. If building materials stay wet for more than 24 to 48 hours, mould can start to grow on the paper face of the plaster and on the framing above. That is why a leaking aircon needs to be fixed at the source and the wet ceiling dealt with, not just painted over.
What We Did
Containment first. Before any plaster came down, we set up containment with plastic sheeting and protected the floor. This keeps the dust from the strip-out inside the work area and away from the rest of the property.
Strip-out. We removed the water-damaged ceiling plaster.
HEPA vacuuming. With the ceiling out, we HEPA vacuumed the walls and other exposed surfaces. How you vacuum matters as much as the machine:
Go slow. Fast strokes skip over fine dust. Slow passes give the HEPA vacuum time to pick it up.
Overlap each pass. Each stroke overlaps the last one a little, so no strip of wall is missed.
Cover every surface. Walls, edges and corners all get the same slow, overlapping passes.
Full PPE. Coveralls, a respirator, gloves and shoe covers for the whole clean.
Watch the HEPA vacuuming on the day, with the original sound:
Independent Clearance
Post-remediation verification (PRV) will be carried out next week by an independent building biologist. Having someone independent of the remediation contractor do the clearance test means the result can be trusted by the owner, the insurer and anyone buying or renting the property later. Rebuilding should only start once the area passes.
Standards We Follow
Our water damage work follows ANSI/IICRC S500, and our mould work follows ANSI/IICRC S520, including containment, HEPA cleaning and independent clearance. Fixing the source of the water, in this case the aircon drip tray and drain, is the owner's responsibility before rebuilding.
What It Costs
This job runs over 6 days and costs $8,000 + GST. The independent PRV is separate. Our mould inspections and quotes are free, and professional moisture and mould reports start from $500 + GST. See our mould removal price guide for more.
For more on our work in the area, see our Eastern Suburbs mould removal page, or read about a nearby subfloor mould job in Matraville.
About the Author
Michael Nguyen is the director of AAA Mould Removal and leads our water damage and mould remediation work across Sydney. His qualifications include:
Indoor Environmental Professional (IEP) – Testing Water-Damaged Buildings, Australian College of Environmental Studies (RTO 21740), 2026. Includes nationally recognised units NAT11429003 Conduct a comprehensive mould and moisture assessment and NAT11429007 Conduct post remediation verification mould testing (11429NAT Advanced Diploma of Building Biology)
IICRC Water Damage Restoration Technician (WRT)
IICRC Applied Microbial Remediation Technician (AMRT)
IICRC Applied Structural Drying (ASD), IICRC no. 69486970
Mould Testing Technician (NAT10913005)
Licensed Builder NSW 392154C (Supervisor, Kitchen, Bathroom & Laundry and Renovation)
Carpentry Licence
AAA Mould Removal is an IICRC Certified Firm. Michael is also completing a double degree in Medical Science and Environmental Science at Macquarie University.
Worried About Mould or Water Damage?
Call AAA Mould Removal on 1300 739 783 or contact us online. We will find the moisture, remove the mould properly and dry your home to IICRC standards.
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