In short: damp and mould in HMOs are usually caused by condensation from cooking, showers and drying clothes, sometimes with leaks or penetrating damp. Councils treat them as hazards, and in Scotland Awaab’s Law sets repair timescales for most private tenancies from 6 October 2026.
Why shared houses get mould
- More people means more moisture: cooking, showers and laundry.
- Rooms are often heated unevenly, leaving cold spots.
- Extraction is often missing, blocked or switched off.
The rules
- England and Wales: damp and mould are assessed under the HHSRS. In England, councils can fine up to £7,000 where a Category 1 hazard is not removed. Awaab’s Law for private renting in England is at consultation.
- Scotland: Awaab’s Law applies to most private tenancies from 6 October 2026: investigate within 10 working days and start repairs to substantial damp or mould within 5 working days.
- Northern Ireland: licence conditions and council enforcement cover disrepair.
Fixing it properly
- Find the cause with moisture readings.
- Fix leaks, gutters and defects.
- Install extraction with overrun or humidity control, or positive input ventilation.
- Insulate cold spots and improve heating.
- Treat and make good, then monitor.
Questions
Is a dehumidifier enough?
It can help, but the cause needs fixing: ventilation, heating and repairs.
Does mould mean rising damp?
Rarely. Condensation is the most common cause in shared houses.
How much does mould treatment cost?
Around £250–£500 per room for treatment and making good, plus whatever is needed to fix the cause.
Checked 31 October 2026. General information for landlords planning works, not legal advice. Check the council’s pages for the exact address.