In short: An HMO extension adds space to a shared house, usually a ground-floor bedroom with ensuite or a bigger communal kitchen. In Gwynedd we survey first, price each item separately and hand over the certificates and photos a council asks for.
- Nation
- Wales
- Pricing region
- Wales
- Postcode areas
- LL, SY
- Main towns
- Bangor (Gwynedd)
What do extensions for extra rooms in Gwynedd involve?
- Heating, insulation and glazing
- Fire separation and detection extended to the new space
- Kitchen or bedroom fit-out
- Party wall coordination where needed
- Planning route check and drawings
- Building control completion
Which rules apply in Gwynedd?
- 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 Gwynedd?
| 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 Gwynedd
Questions about extensions for extra rooms in Gwynedd
Is a kitchen extension worth it?
Often, when the existing kitchen limits how many people the council will allow. A bigger kitchen can unlock an extra room.
Do you handle building control?
Yes, from application to completion certificate.
Do you carry out extensions for extra rooms across Gwynedd?
Yes, across the whole of Gwynedd, including Bangor (Gwynedd).
Who licenses HMOs in Gwynedd?
Gwynedd council licenses HMOs in its area. Landlords must also register with Rent Smart Wales.
Other HMO services in Gwynedd
- Loft conversions for extra rooms in Gwynedd
- Communal kitchen refits in Gwynedd
- Layout changes and room reconfiguration in Gwynedd
- Large HMO conversions (7+ sharers) in Gwynedd
- Ensuite installation in Gwynedd
- House to HMO conversion in Gwynedd
- Sound insulation in Gwynedd
- Professional and co-living HMO refurbs in Gwynedd