Cleaning removes visible growth but does not change the conditions that allowed it to develop. Mould can return while a surface remains persistently damp, whether from condensation, a leak, rainwater entry or another building defect.
Common reasons for recurrence
- Bathroom or kitchen extraction is absent, ineffective, switched off too soon or poorly ducted.
- Cold corners, lintels or walls remain below the temperature of surrounding surfaces.
- Furniture restricts air movement against an external wall.
- A plumbing, roof, gutter or external-wall defect continues to supply moisture.
- Heating and ventilation patterns allow humidity to remain high for long periods.
Choose the response after diagnosis
The next step may be improved source extraction, background ventilation, a repair to the building fabric, or a review of insulation and heating. A PIV unit is not automatically the right answer, and decorating over mould before the surface is clean and dry can conceal rather than solve the problem.
For health symptoms or advice about cleaning products, consult an appropriate medical or product-safety source. A building inspection addresses the property conditions, not personal medical diagnosis.