In short: An HMO extension adds space to a shared house, usually a ground-floor bedroom with ensuite or a bigger communal kitchen. We carry this out across Cornwall, priced against the HMO rules for England and the council’s own standards.
- Nation
- England
- Pricing region
- South West
- Postcode areas
- PL, TR, EX
- Main towns
- Redruth, Falmouth, St Austell, Truro, Camborne
What do extensions for extra rooms in Cornwall involve?
- Fire separation and detection extended to the new space
- Party wall coordination where needed
- Planning route check and drawings
- Kitchen or bedroom fit-out
- Heating, insulation and glazing
- Building control completion
Which rules apply in Cornwall?
- 3–6 unrelated sharers is use class C4; changing from a family house is usually permitted development unless an Article 4 direction applies.
- Building regulations cover structural changes, new partitions, ensuite drainage, fire-resisting construction and notifiable electrical work.
- Smoke alarms on every storey with living accommodation and CO alarms by fixed combustion appliances (other than gas cookers) are required by law.
- National rules ask for an adequate number of bathrooms, WCs and basins and suitably located kitchens; numeric ratios are set by each council.
- 7 or more sharers is a sui generis large HMO and normally needs planning permission.
Councils in England can add additional licensing and Article 4 directions on top of the national rules. Check the council’s website for the exact address before you buy or start work.
How much do extensions for extra rooms cost in Cornwall?
| Item | UK typical | Local guide | Per |
|---|---|---|---|
| Single-storey extension, about 15 m² | £35,000 – £60,000 | £36,400 – £62,400 | project |
| Single-storey extension per m² | £1,800 – £4,000 | £1,850 – £4,150 | 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 Cornwall
Questions about extensions for extra rooms in Cornwall
Do you handle building control?
Yes, from application to completion certificate.
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 carry out extensions for extra rooms across Cornwall?
Yes, across the whole of Cornwall, including Redruth, Falmouth, St Austell.
Who licenses HMOs in Cornwall?
HMOs in Cornwall are licensed by the local council for the address. Where an area has several councils, each runs its own licensing and planning policies.
Other HMO services in Cornwall
- Loft conversions for extra rooms in Cornwall
- Communal kitchen refits in Cornwall
- Layout changes and room reconfiguration in Cornwall
- Large HMO conversions (7+ sharers) in Cornwall
- Ensuite installation in Cornwall
- House to HMO conversion in Cornwall
- Sound insulation in Cornwall
- Professional and co-living HMO refurbs in Cornwall