In short: An HMO loft conversion adds one or two letting rooms, often with an ensuite, in the roof space. We carry this out across Cardiff, priced against the HMO rules for Wales and the council’s own standards.
- Nation
- Wales
- Pricing region
- Wales
- Postcode areas
- CF
- Main towns
- Cardiff, Whitchurch
What do loft conversions for extra rooms in Cardiff involve?
- New stair within the protected route
- Ensuite where space allows
- Structural design and steelwork
- Building control sign-off
- Fire doors and extended alarm system
- Feasibility and head-height check
Which rules apply in Cardiff?
- 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.
- Council HMO standards and the fire risk assessment set detection, fire doors and escape routes.
- England’s national room sizes do not apply in Wales; councils set their own room standards.
- Mandatory licence for HMOs with 3 or more storeys and 5 or more people in 2 or more households; Wales did not adopt England’s 2018 change.
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 loft conversions for extra rooms cost in Cardiff?
| Item | UK typical | Local guide | Per |
|---|---|---|---|
| Dormer loft conversion, about 30 m² | £40,000 – £60,000 | £37,600 – £56,400 | project |
| Rooflight loft conversion, about 30 m² | £22,500 – £30,000 | £21,150 – £28,200 | project |
Typical time on site: 6–10 weeks. For a figure for your house, try the guide-price tool.
Loft conversions for extra rooms by town in Cardiff
Questions about loft conversions for extra rooms in Cardiff
Does a loft room need a fire escape window?
In an HMO the main protection is usually a protected stair and fire doors. The building regulations and fire strategy decide the detail.
How much head height do I need?
As a rule of thumb, about 2.2 metres at the highest point of the existing roof space before any work. Less can work with a dormer or lowered ceilings.
Do you carry out loft conversions for extra rooms 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.
Other HMO services in Cardiff
- Extensions for extra rooms in Cardiff
- Large HMO conversions (7+ sharers) in Cardiff
- Escape routes, emergency lighting and fire stopping in Cardiff
- Ensuite installation in Cardiff
- Layout changes and room reconfiguration in Cardiff
- Fire alarm and detection systems in Cardiff
- Licence condition and schedule-of-works in Cardiff
- EPC and energy upgrades in Cardiff