In short: An HMO extension adds space to a shared house, usually a ground-floor bedroom with ensuite or a bigger communal kitchen. Across Monmouthshire, the work is planned around Wales’s HMO rules and the standards the local council publishes.
- Nation
- Wales
- Pricing region
- Wales
- Postcode areas
- NP
- Main towns
- Brynmawr, Abergavenny
What do extensions for extra rooms in Monmouthshire involve?
- Foundations, structure and roof
- Heating, insulation and glazing
- Fire separation and detection extended to the new space
- Planning route check and drawings
- Ensuite drainage and extraction
- Kitchen or bedroom fit-out
Which rules apply in Monmouthshire?
- 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.
- Fitness for human habitation rules require mains-powered, interlinked smoke alarms on every storey and CO alarms where there is a gas, oil or solid-fuel appliance.
- Kitchen and bathroom ratios are set in each council’s HMO standards.
- More than 6 sharers is a sui generis HMO and needs planning permission; councils such as Cardiff apply concentration limits.
Welsh councils set their own HMO standards and may run additional licensing. In Wales, changing a house to a C4 HMO always needs planning permission, so check planning first.
How much do extensions for extra rooms cost in Monmouthshire?
| Item | UK typical | Local guide | Per |
|---|---|---|---|
| Single-storey extension, about 15 m² | £35,000 – £60,000 | £32,900 – £56,400 | project |
| Single-storey extension per m² | £1,800 – £4,000 | £1,700 – £3,750 | m² |
Typical time on site: 8–14 weeks. For a figure for your house, try the guide-price tool.
Extensions for extra rooms by town in Monmouthshire
Questions about extensions for extra rooms in Monmouthshire
Can I extend an HMO under permitted development?
Some extensions to houses are permitted development, but rules differ for HMOs and by nation and council. We check the address before design.
Will the extension affect neighbours?
Possibly, if it is on or near a boundary. Party wall procedures may apply in England and Wales.
Do you carry out extensions for extra rooms across Monmouthshire?
Yes, across the whole of Monmouthshire, including Brynmawr, Abergavenny.
Who licenses HMOs in Monmouthshire?
Monmouthshire council licenses HMOs in its area. Landlords must also register with Rent Smart Wales.
Other HMO services in Monmouthshire
- Loft conversions for extra rooms in Monmouthshire
- Communal kitchen refits in Monmouthshire
- Layout changes and room reconfiguration in Monmouthshire
- Large HMO conversions (7+ sharers) in Monmouthshire
- Ensuite installation in Monmouthshire
- House to HMO conversion in Monmouthshire
- Sound insulation in Monmouthshire
- Rewires and EICR remedials in Monmouthshire