Large HMO conversions across Cardiff

In short: A large HMO is a shared house for seven or more people. Across Cardiff, the work is planned around Wales’s HMO rules and the standards the local council publishes.

Nation: Wales
Pricing region: Wales
Postcode areas: CF
Main towns: Cardiff, Whitchurch

What do large HMO conversions (7+ sharers) in Cardiff involve?

Sound insulation between rooms and floors
Emergency lighting where the escape route needs it
Ensuites or extra bathrooms
Protected stair and landing with fire doors and fire stopping
Planning and building control drawings, coordinated with your designer
Second kitchen or extra kitchen capacity

Which rules apply in Cardiff?

Landlords must register with Rent Smart Wales, and those who manage their own lets need a Rent Smart Wales licence.
England’s national room sizes do not apply in Wales; councils set their own room standards.
Kitchen and bathroom ratios are set in each council’s HMO standards.
3–6 sharers is use class C4, and in Wales changing a house to C4 always needs planning permission; only C4 back to C3 is permitted development.
Building regulations cover structural work, partitions, drainage, fire-resisting construction and electrics; confirm with building control whether the conversion is a material change of use.

Cardiff Council: local HMO schemes

Additional licensing	In force in part of the council area Cathays: 1 Feb 2023 to 1 Feb 2028. Plasnewydd had a scheme from 1 Jan 2021; check with Cardiff Council whether it has been renewed.
Selective licensing	No scheme found

Schemes change. Check the council’s current pages for the exact address in Cardiff before you buy or start work. Source: Cardiff Council HMO licensing page, checked 2026-10-31.

How much do large HMO conversions (7+ sharers) cost in Cardiff?

Regional adjustment for Wales. Planning budgets: see our prices page.
Item	UK typical	Local guide	Per
Conversion works per letting room (walls, linings, electrics, decoration; excludes kitchens, bathrooms and fire systems; our estimate)	£3,500 – £6,500	£3,300 – £6,100	letting room
Panel alarm system (Grade A type), larger HMO	£1,750 – £4,500	£1,650 – £4,250	house
Protected route upgrades: fire-resisting linings, fire stopping, lighting (three-storey house, our estimate)	£2,000 – £6,000	£1,900 – £5,650	house
Ensuite shower room added to a bedroom	£4,000 – £10,000	£3,750 – £9,400	ensuite
Communal HMO kitchen with extra cooking and sink capacity (our estimate from domestic ranges)	£8,000 – £18,000	£7,500 – £16,900	kitchen

Typical time on site: 10–20 weeks. For a figure for your house, try the guide-price tool.

Large HMO conversions (7+ sharers) by town in Cardiff

Questions about large HMO conversions (7+ sharers) in Cardiff

What fire alarm does a large HMO need?

The fire risk assessment and the council decide; alarm grades come from guidance, not statute. For larger HMOs, council guides and the NI fire service guide commonly point to a Grade A panel system covering escape routes and rooms. We fit to the specification set, and give you the commissioning certificate.

Do you handle building control?

Yes. The building work in a large HMO conversion (partitions, fire separation, drainage, electrics) needs to meet the building regulations, and the conversion can also count as a material change of use. We confirm the route with building control, coordinate inspections and give you the completion paperwork.

Do you carry out large HMO conversions (7+ sharers) across Cardiff?

Yes, across the whole of Cardiff, including Cardiff, Whitchurch.

Who licenses HMOs in Cardiff?

Cardiff council licenses HMOs in its area. Landlords must also register with Rent Smart Wales.

Large HMO conversions (7+ sharers) across Cardiff