Garage conversions with a room above in Oxfordshire

Oxfordshire at a glance

Nation: England
Price region: South East England
Postcode areas: OX, RG, SN
Towns covered: 13 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.

Towns in Oxfordshire include Oxford (OX1), Banbury (OX15), Abingdon (OX13), Bicester (OX6), Didcot (OX11) and Witney (OX7). If yours isn't listed, we still cover it.

Guide price in South East England

Using our South East England rates, a garage conversion with a room above with 3 m × 6 m of new first-floor space (18 m²) comes to about £34,500–£50,500 (for the room above; converting the garage itself is priced after the survey), including VAT. Bigger or more glazed designs cost more per m². Design fees, structural calculations and approval fees are separate and listed on our prices page.

Spec	Per m²	Typical project
Essential	£1,770–£2,580 per m²	£32,000–£46,500
Standard	£1,930–£2,800 per m²	£34,500–£50,500
Premium	£2,310–£3,370 per m²	£41,500–£60,500

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

Raising and insulating the floor

Garage floors are usually lower than the house and have no insulation or damp-proof membrane. We raise the floor to meet the house level where possible, with insulation and a membrane, so the converted room is warm and dry and does not have a step down.

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 Oxfordshire

Measure and listen
A visit to Oxfordshire to understand how you live in the house now and what the extra rooms need to do, plus a first look at the structure.
Get it approved
Once you're happy with the design we submit it to the council for Oxfordshire and deal with any questions from the planning officer.
Technical design
We prepare the building regulations drawings, structural calculations and specification so the build price can be fixed.
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 Oxfordshire

Garage conversions with a room above in Oxfordshire: questions

How much does a garage conversion with a room above cost in Oxfordshire?

In South East England our guide is £1,930–£2,800 per m² including VAT, so about £34,500–£50,500 (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.

Is it worth converting the garage at the same time as building above it?

Usually, yes. Building a room above often means upgrading the garage foundations and walls anyway, so converting it at the same time spreads that cost over two rooms. You also have one period of disruption, one set of drawings and one building regulations approval instead of two.

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.

Does the room above need a fire door if the garage is converted?

Once the garage becomes a habitable room, the fire separation needed between a garage and the house usually falls away. The new bedroom above still needs an escape window or a protected route to the stairs, and smoke alarms. If you keep part of the garage for storage, separation may still be needed, which we confirm with building control.

Will I need planning permission in Oxfordshire?

Oxfordshire is in England. Planning permission is needed: in England, permitted development only allows single-storey extensions to the side.

Neighbouring areas

All extension services in Oxfordshire · About garage conversions with a room above