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Australian home problem guide

Mould keeps returning

Recurring mould is usually a moisture problem. Cleaning alone will not solve a leak, condensation, ventilation or waterproofing defect.

General guidance, not an inspection or diagnosis. Repair advice has not been independently reviewed by a tradesperson. How these guides are prepared.

What to do now

First step

Avoid disturbing large mould-affected areas if you have health concerns or the material is extensively contaminated. Find and stop the moisture source.

Common causes

  • Condensation / poor ventilation
  • Roof or plumbing leak
  • Waterproofing defect
  • Subfloor or rising damp issue

The exact cause cannot be confirmed from a symptom alone. The first professional should inspect before repair work is authorised.

What the professional may do next

  1. Identify moisture source
  2. Measure / inspect affected area
  3. Fix leak or ventilation problem
  4. Clean or remediate affected materials

What should I ask about the price?

Ask for an itemised quote covering the inspection or call-out fee, labour, materials, GST, access, disposal and any after-hours charge. Ask what happens if extra damage is found. A reliable price needs details of the actual job; this guide does not provide an estimate.

Who may be responsible?

Owner / landlord / strata

Responsibility depends on whether mould results from a building defect, leak, ventilation issue or occupant-related moisture.

Tenancy, strata, insurance and boundary responsibilities vary by circumstance and state, so confirm responsibility before non-emergency work where practical.

Questions to ask before hiring

  • Are you appropriately licensed or registered for this work in my state?
  • Does the quote include call-out, labour, parts/materials, GST and disposal?
  • What is excluded from the quoted scope?
  • If you find additional damage, will you get approval before doing extra work?
  • What workmanship or product warranty applies?

Look for a pattern, not a diagnosis

Record the rooms affected, when the patches return and any visible condensation or staining. Recurring mould can be associated with different moisture sources. A visual description cannot reliably distinguish condensation, a leak or a building defect.

Choose help for the underlying moisture

Ask a building moisture inspector what their assessment includes and what evidence they provide. A known plumbing leak may need a plumber; rain-related water entry may need roof assessment. Cleaning a surface alone will not repair an underlying moisture defect.

What to ask before approving work

Does the proposal investigate the moisture source, address a confirmed defect or only clean affected surfaces? Ask how the need for specialist remediation will be assessed and what follow-up checks are included. Do not disturb suspected hazardous materials.

Sources and review status

Prepared for Home Triage Australia. Updated 25 October 2026. This guide has not been independently reviewed by a qualified tradesperson. The sources below support general maintenance and hiring principles, not a diagnosis of your property.

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