Garage conversions with a room above in Cornwall
Cornwall has a wide mix of house types, and most can take a well-designed garage conversion with a room above. Here's what's involved, the rules in England and typical costs.
Cornwall at a glance
- Nation
- England
- Price region
- South West England
- Postcode areas
- PL, TR
- Towns covered
- 10 listed below, plus surrounding villages
- Approval route
- Planning permission is needed: in England, permitted development only allows single-storey extensions to the side.
- Site visits
- Free, no obligation
What a garage conversion with a room above involves
A garage conversion with a room above is a project that turns an attached garage into living space and builds a new room on top, so you gain space on both floors in one build. It suits a single garage beside the house that is no longer used for a car. Doing both together means the walls, foundations and insulation are upgraded once.
The main places we list in Cornwall are Redruth (TR5), Falmouth (TR10), St Austell (PL23), Truro (TR1), Camborne (TR14) and Newquay (PL28). We cover the villages in between too.
Guide price in South West England
Our guide for South West England is £1,800–£2,630 per m² including VAT. On a project with 3 m × 6 m of new first-floor space (18 m²), that puts a garage conversion with a room above in Cornwall at roughly £32,500–£47,500 (for the room above; converting the garage itself is priced after the survey). Keep a contingency of around 10% for things nobody can see until the ground is opened up.
| Spec | Per m² | Typical project |
|---|---|---|
| Essential | £1,660–£2,420 per m² | £30,000–£43,500 |
| Standard | £1,800–£2,630 per m² | £32,500–£47,500 |
| Premium | £2,160–£3,150 per m² | £39,000–£56,500 |
Rules in England
In England, converting a garage on its own often needs no planning permission, but building a room above a side garage makes a two-storey extension beyond a side wall, which needs planning permission costing £548 (or £575 for applications made from 8 December 2026). Some estates have conditions removing garage conversion rights, which we check first.
Approval in England: Householder planning application: £548 (or £575 for applications made from 8 December 2026). Lawful development certificate: £274 (about £288 for applications from 8 December 2026). Councils should decide householder applications within 8 weeks of validation.
Building regulations: Building regulations approval (full plans recommended) from the council or a registered building control approver, with a completion certificate at the end.
The Party Wall etc. Act 1996 applies, so notices may be needed for work on or near a shared wall or boundary.
Getting the design right
Stairs and access
The room above is usually reached from the existing landing, while the converted garage opens off the hall. If the levels do not work, a new stair inside the converted garage can serve the room above, which we test in the layout.
Infilling the garage door
The garage door opening is usually filled with a new wall and a window, on a new foundation, with brick to match. The new front wall needs a cavity, insulation and a damp-proof course, and the window position should line up with the room above.
How we work in Cornwall
Visit and first ideas
One of our team visits your house in Cornwall, checks the walls, roof and drains, and sketches out options with you.
Choose the approval route
Some designs fit permitted development, most need a householder application. We decide which applies in England before drawing in detail.
Structure and building control
A structural engineer sizes the foundations and steels, and we get building regulations approval before work starts.
Build
Foundations, walls, floor, roof, windows, then first and second fix. We break through into the house as late as we can.
Towns we cover in Cornwall
Garage conversions with a room above in Cornwall: questions
How much does a garage conversion with a room above cost in Cornwall?
In South West England our guide is £1,800–£2,630 per m² including VAT, so about £32,500–£47,500 (for the room above; converting the garage itself is priced after the survey) for 3 m × 6 m of new first-floor space (18 m²). Essential and Premium specs move that by roughly 8% down or 20% up.
Do I need planning permission to convert my garage?
In England, converting an attached garage to a room often needs no planning permission when the work is internal, unless a condition or Article 4 direction removes that right. Building regulations approval is always needed. The room above usually needs planning permission when the garage is at the side.
How warm will a converted garage be?
As warm as the rest of the house, if it is built properly. In England the new walls, floor and roof must meet limiting U-values of 0.18 W/m²K for walls and floors and 0.15 for roofs, and new windows 1.4. We add insulation and a damp-proof membrane, and extend the heating.
Will losing the garage affect parking?
It can. If the garage counts towards required parking on your estate, the council may look at whether enough off-road spaces remain. Most households in practice park on the drive. We check your title and any planning conditions about the garage at the start.
Will I need planning permission in Cornwall?
Cornwall is in England. Planning permission is needed: in England, permitted development only allows single-storey extensions to the side.
Neighbouring areas
- Garage conversions with a room above in Devon
- Garage conversions with a room above in Swansea and Neath Port Talbot
- Garage conversions with a room above in Dyfed
- Garage conversions with a room above in Cardiff and the Vale of Glamorgan
All extension services in Cornwall · About garage conversions with a room above
Ready to see what a second storey could do for your home?
Book a free site visit. We'll look at your house, talk through options and explain the approvals you'd need, then price the design stage in writing.