Subfloor Mould Remediation in Leichhardt, Sydney: Uncovering the Hidden Danger

image taken during mould inspection of the subfloor in Leichhardt shows the floor joist has mould growth

By Michael Nguyen — AAA Mould Removal

Introduction: Why Subfloor Mould Is More Than Just a Cosmetic Issue

Mould beneath your home poses a serious threat to your property's structure and your family’s health. Left untreated, it can weaken timber supports, reduce indoor air quality, and trigger respiratory illnesses. When a homeowner in Leichhardt, part of Sydney’s Inner West, contacted us about a persistent musty smell, our inspection revealed a severe case of subfloor mould — and we delivered a full-service remediation that followed industry best practice.

This video is a subfloor inspection completd by one of our mould inspection at a site in Leichhardt fromour Youtube Channel https://www.youtube.com/@aaamouldremoval9147

The Discovery: Rising Damp and Severe Subfloor Mould

First Warning Signs

The client reached out when they noticed musty air and suspected something lurking under their timber floors. During our professional mould inspection, we entered the crawl space and found widespread visible mould growth across all timber joists, especially in a low-lying section where the infestation was densest.

Diagnosing the Root Cause

We quickly identified the source: rising damp caused by water ingress from the soil under the house footings. Humidity levels in the subfloor ranged between 80% and 100%, particularly during Sydney’s recent heavy rains — creating the perfect breeding ground for mould.

Scientific Assessment: Sampling & Monitoring for a Data-Driven Plan

Air & Surface Mould Sampling

We collected both air and surface samples throughout the subfloor. Lab results confirmed elevated levels of Aspergillus/Penicillium species, which are reliable indicators of moisture-related contamination.

Environmental Data Logging

To verify ongoing moisture patterns, we installed data logging equipment for 10 days. These loggers continuously recorded dangerously high humidity, confirming the chronic nature of the problem and helping us plan an effective long-term solution.

A section of the yellow tounge was remove and dispose due to heavy mould growth and cannot be cleaned

Our Remediation Process: IICRC S520-Backed and Built for Results

At AAA Mould Removal, we follow the internationally recognised IICRC S520 Standard for Professional Mould Remediation to ensure health, safety, and effectiveness.

Phase 1: Containment & Pre-Cleaning

• Negative air setup using HEPA-filtered scrubbers

• Thorough HEPA vacuuming of all accessible timber

• Damp wiping with an antimicrobial solution

• Secondary HEPA vacuuming to eliminate dislodged spores

  
  

Phase 2: Deep Treatment for Inaccessible and Embedded Mould

• Hydrogen peroxide spray for hard-to-reach areas and porous timber

• Sanding of severely affected surfaces to remove top layers of contamination

• Dry ice blasting — a moisture-free, non-abrasive solution ideal for delicate timber

See the full breakdown of our mould removal process and black mould remediation methods.

Phase 3: Structural Drying and Humidity Control

• Use of Drymatic Thermal Drying System for rapid timber drying

• Air movers and commercial dehumidifiers to pull moisture from the subfloor

• This step was vital to prevent immediate regrowth and stabilize timber moisture content

Phase 4: Final Mould Testing

We performed post-remediation mould monitoring to confirm that airborne spores and surface contaminants had returned to safe levels. This validated that the remediation was successful.

Phase 5: Independent Hygienist Verification (PRV)

To ensure transparency, we engaged an independent occupational hygienist to perform a Post-Remediation Verification (PRV). Their sampling confirmed a mould-safe environment, giving the homeowner total peace of mind.

Part of the subfloor after the first round of HEPA Vacuum as part of phase 1 mould removal

Project Snapshot

• Location: Leichhardt, Inner West Sydney

• Treatment Area: 150 m² subfloor

• Timeline: 7 days

• Cost: $8,000 (includes inspection, remediation, drying, sampling & lab reports)

• Status: Cleared by internal QA and third-party PRV

  
  

Outcome: A Safer, Healthier Home in Sydney’s Inner West

The homeowner now enjoys a clean, dry subfloor with significantly improved indoor air quality. The musty smell is gone, structural timber is safe, and the environment is no longer hospitable to mould.

“The crawl space is now dry, and the smell is completely gone. It feels like a new home underfoot.”— Leichhardt Homeowner

Book Your Mould Inspection Today

If you're noticing damp odours, musty air, or timber damage, it could be hidden mould.

Learn why a mould inspection is your first defence and get:

• Air & surface testing

• Environmental data logging (if needed)

• A full science-backed remediation plan

• Optional independent hygienist verification

  
  

Call AAA Mould Removal or request your inspection online.Your home's health starts with what’s beneath your feet.

About the Author

Michael Nguyen is the founder of AAA Mould Removal and a leading expert in mould remediation and building science. His mission is to help Sydney residents maintain healthy indoor environments through scientifically-backed, professional remediation services.

With a unique combination of hands-on and academic expertise, Michael's qualifications are extensive:

• IICRC Certified: Water Damage Restoration, Applied Microbial Remediation & Applied Structural Drying.

• Microbiology: Completed specialised study in Microbiology at RMIT University.

• Licensed Builder & Carpenter with a Diploma in Building & Construction.

• Current University Studies: Double Bachelor’s degree in Medical Science and Environmental Science at Macquarie University.

This deep understanding of building structures, environmental science, and microbiology allows Michael to diagnose the root cause of mould problems, not just treat the symptoms. He specialises in residential and commercial mould removal, black mould treatment, and water damage restoration.

Need a true expert to assess your property? Contact AAA Mould Removal today for a comprehensive mould inspection.