Integral · Detached · Annexe · Fixed price
Garage Conversions in London
Integral and detached garage conversions across London. Full insulation to walls, floor and ceiling. Electrics, plastering and decoration. Building Regulations managed and completion certificate provided. Fixed price before we start.
Types of garage conversion we deliver
Every garage conversion is different — the structure, the use, and whether planning is needed all vary. We assess all of this for free before you commit.
Integral garage conversion
The most common type in London. Your garage is already attached to and part of the main house structure. We remove the garage door, insulate the walls, floor and ceiling to current Building Regulations standards, add a window or door, rewire for electrics, and plaster and finish to habitable room standard.
Guide cost: £18,000–£30,000
Detached garage conversion
Freestanding garage in the garden converted to a habitable room, home office, studio or annexe. Typically requires a connection for electrics and potentially plumbing. May require planning permission depending on use and size.
Guide cost: £20,000–£40,000
Garage conversion with extension over
Convert the garage and build above it at the same time — adding a bedroom, bathroom or study above the new habitable room. Structural engineer coordinated. Usually requires planning permission.
Guide cost: £55,000–£90,000
Garage to annexe or rental unit
Fully self-contained living unit within a garage structure. Kitchen, bathroom, bedroom and living space. Change of use planning permission required. Building Regulations managed throughout.
Guide cost: £40,000–£70,000
What a garage conversion includes
Garage door removal & infill
- ✓Garage door and frame removed
- ✓Opening infilled with brick or block to match existing
- ✓New window installed in former door opening
- ✓Or new French / bifold doors where preferred
- ✓Lintel and structural head retained or upgraded
Insulation to Building Regulations
- ✓Wall insulation — internal thermal board or full external wall wrap
- ✓Floor insulation — rigid insulation board beneath new screed or boarding
- ✓Ceiling insulation — above new plasterboard ceiling
- ✓Draught sealing to all openings
- ✓All insulation to current Part L standards
Electrical works
- ✓New consumer unit circuit or extension from main board
- ✓Sockets, switches and lighting to agreed positions
- ✓Heating provision — radiator connected to existing system or electric
- ✓EV charger provision where specified
- ✓TV aerial and data point where specified
Plastering and finishing
- ✓Full plasterboard and skim to all walls and ceiling
- ✓Coving where matching existing rooms
- ✓Skirting boards and architraves
- ✓Door from house into converted room where specified
- ✓Mist coat and two coats of emulsion
Floor finishes (carpet, LVT, tiles) are client-supplied unless specifically agreed otherwise. RCB does not install carpet.
How we manage your garage conversion
Survey and planning check
We visit, assess the garage structure and advise on whether planning permission is required. Most integral garage conversions are permitted development — we confirm this before you spend anything.
Structural assessment
We check the existing slab, walls and roof structure. If the conversion goes above the garage, we coordinate a structural engineer. For a standard conversion, no SE is normally required.
Fixed price issued
Written scope and fixed price — insulation, electrics, plastering, window/door, decoration included. No hidden extras.
Building Control notification
We notify Building Control before work starts and manage all inspections. Thermal insulation, ventilation, and electrics are all inspected. You receive a completion certificate.
Works on site
Garage door removed and opening closed up or infilled. Insulation to walls, floor and ceiling. First fix electrics. Plastering. Window and door installation. Second fix electrics. Decoration.
Completion
Building Control sign-off and completion certificate issued. Room handed over clean and fully finished — ready to use as a habitable room immediately.
Why choose RCB Design & Build?
Planning checked upfront
We confirm whether your conversion needs planning permission before work starts. No nasty surprises after you've committed.
Building Regulations managed
We handle the notification, manage all inspections, and provide the completion certificate. This is essential for selling or remortgaging later.
Fixed price guaranteed
Your price is agreed before work starts and doesn't change unless you change the scope. We absorb material and labour cost movements.
4–6 week programme
A standard garage conversion is a clean, fast project. We give you a programme before we start so you know exactly when you'll have your new room.
All trades managed
Bricklaying, carpentry, electrical and plastering are all managed by our team. You don't coordinate multiple contractors.
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Garage conversion questions answered
Do I need planning permission for a garage conversion in London?
For an integral garage conversion that does not extend beyond the existing footprint and does not create a self-contained unit, planning permission is usually not required — it is permitted development. However, if you live in a conservation area, a listed building, or an area with an Article 4 Direction removing permitted development rights, planning permission may be required. Detached garages and annexes with kitchens and bathrooms (self-contained units) almost always require a change of use planning application. We check this for your specific property before starting.
Do garage conversions need Building Regulations approval?
Yes. All garage conversions that create a habitable room require Building Regulations approval. The inspection covers thermal insulation (walls, floor, ceiling to Part L standards), ventilation, electrics, structural stability, and fire safety where the garage is attached to the house. We manage the Building Control notification and all inspections as part of the project.
How much does a garage conversion cost in London?
An integral garage conversion to a habitable room in London typically costs £18,000–£30,000. This includes removing the garage door and closing up the opening, full insulation to all walls and ceiling, concrete floor insulation or replacement, electrics, plastering, a new window or French doors, and decoration. Detached garages, annexes, and conversions with plumbing (bathroom, kitchenette) cost more — typically £25,000–£50,000.
How long does a garage conversion take?
A standard integral garage conversion typically takes 4–6 weeks on site. A detached garage conversion or an annexe project with plumbing and a bathroom typically takes 6–10 weeks. We issue a programme before work starts.
Can a garage conversion add value to my property?
Yes — converting a garage to a habitable room typically adds more value to a London property than a garage provides. In most parts of London, an additional bedroom, home office, or reception room is worth significantly more to buyers than parking or storage. The main exception is if the property has no off-street parking at all — the loss of covered storage may be a factor in some markets.
Can I convert my garage to a home office or gym?
Yes. A garage converted to a home office, gym, studio or playroom follows the same Building Regulations process as a bedroom conversion. The thermal insulation and ventilation standards are the same. The only difference with a bedroom conversion is fire safety requirements where the garage is integral to the house — we manage this as part of the project.
Convert your garage — free survey
Planning checked. Fixed price. Building Regulations managed. 4–6 week programme. One team from survey to sign-off.
Or call 07359 872594