House to HMO conversion across Cardiff

In short: A house to HMO conversion turns a single-family home into a house in multiple occupation: a shared home for unrelated people with private bedrooms and shared kitchen or bathroom space. 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 does house to HMO conversion in Cardiff involve?

A communal kitchen sized for the number of sharers
Fire doors, fire-rated linings and an interlinked fire alarm
New stud walls, door openings and room splits
Decoration, flooring and a handover pack for licensing
Measured survey and room-size check against the licensing standards
Extra bathrooms, shower rooms or ensuites

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 does house to HMO conversion cost in Cardiff?

Regional adjustment for Wales. Planning budgets: see our prices page.
Item	UK typical	Local guide	Per
Typical 3–4 bed house to a 5–6 bed HMO, all-in	£30,000 – £75,000	£28,200 – £70,500	project
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
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
Interlinked mains alarm system (Grade D type), small HMO (our estimate from installer guides)	£800 – £2,000	£750 – £1,900	house

Typical time on site: 6–14 weeks. For a figure for your house, try the guide-price tool.

House to HMO conversion by town in Cardiff

Questions about house to HMO conversion in Cardiff

How long does a house to HMO conversion take?

Most conversions of a three or four-bedroom house take six to fourteen weeks on site, after drawings and any approvals. Bigger layout changes, extensions or loft rooms add time.

Can you work to a council’s HMO standards document?

Yes. Councils publish their own amenity and space standards. We read the one for your address and work to it, including kitchen and bathroom ratios.

Do you carry out house to HMO conversion 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.