A garage conversion in the West Midlands costs between £12,000 and £30,000 in 2026. For most single integral garages turned into a habitable room, the figure lands around £14,000 to £20,000.
It is the cheapest way to add a proper room to a house, and the reason is simple: the walls, the foundations and the roof already exist. You are not digging, you are not building a superstructure, and you are not waiting on a planning decision. Compare that with a single-storey extension at £45,000 and up for similar floor area and the arithmetic makes itself.
The catch is that a garage was never built to be lived in, and the cost sits almost entirely in the work required to change that.
What a garage conversion costs in 2026
West Midlands ranges for a full conversion — insulating the floor, walls and ceiling, building up the door opening, new window, electrics, heating, plastering and finishes.
| Type of conversion | Typical range | What that buys |
|---|---|---|
| Single integral garage → room | £12,000 – £18,000 | Habitable room, insulated and heated, new window, decorated |
| Single garage → room with shower | £18,000 – £25,000 | As above plus drainage, WC and shower room |
| Double garage → open-plan room | £20,000 – £30,000 | Larger span, more glazing, sometimes structural work |
| Detached garage → office or annexe | £25,000 – £40,000 | Services run from the house, separate heating, higher insulation spec |
Why garages are cheap to convert and expensive to get wrong
Three things about a garage make it unfit to live in, and all three cost money to fix.
The floor is the first. Garage slabs are usually laid lower than the house floor, often without a damp-proof membrane, and frequently laid to a fall so water runs out of the door. Bringing it up to level, insulated and damp-proofed, is the single biggest line item in most conversions.
The walls are the second. Many garages, especially on estates built from the 1960s onwards, are single-skin brick with no cavity and no insulation. They have to be insulated internally, which costs money and eats roughly 100mm off each external wall — worth knowing before you plan furniture.
The third is the door opening. Bricking it up properly means matching the existing brick, tying into the existing walls, and building off a foundation that can carry it. Building off the edge of an old slab is a common shortcut and a common source of cracking a couple of years later.
Do you need planning permission?
Usually not. Converting a garage into a habitable room is normally permitted development, provided the work is internal and you are not enlarging the building. That is why it is such a quick win compared with an extension.
There are exceptions, and they matter locally. Some estates carry a planning condition requiring the garage to be retained as parking — this is common on newer developments and on some Sutton Coldfield and Solihull estates. Flats and maisonettes do not have permitted development rights at all. Listed buildings and some conservation areas will need consent.
If you are changing the external appearance significantly — putting in large glazing where the door was, for instance — that can also tip it into needing an application. Worth checking before you commit.
Building Regulations always apply
This is the part people miss. Planning permission and Building Regulations are two different things, and while you often escape the first, you never escape the second. Converting a garage to habitable space is a material change of use and requires Building Control approval.
That covers thermal insulation to current Part L standards, fire safety and escape, ventilation, structural adequacy of the new wall in the door opening, damp-proofing, and electrical work certificated under Part P.
Getting sign-off matters beyond the legality. Without a completion certificate the conversion is a problem at resale — buyers' solicitors ask for it, and an unregularised conversion can hold up or reduce an offer. A conversion done without Building Control is not a cheaper conversion, it is a deferred cost.
What it is worth doing to the specification
Two upgrades pay for themselves. Insulate above the minimum — the difference in cost between meeting Part L and comfortably beating it is small, and a converted garage is usually the coldest room in the house because it has three external walls.
The second is heating. Extending the existing central heating into the room is almost always better than an electric panel heater, provided the boiler has the capacity. Retro-fitting it later means lifting the new floor you have just laid.
Keep some storage if you can. The most common regret is losing every bit of storage the house had. A partition leaving a metre of depth at the front for bikes and bins costs very little and preserves most of the practical use of the space.
How long it takes
Four to eight weeks on site for a standard single garage. A conversion including a shower room runs closer to eight. Detached garage conversions take longer because services have to be run from the house.
Add three to four weeks beforehand for drawings, structural calculations where the opening is being altered, and the Building Regulations submission. Building Control will want to inspect at foundation, damp-proofing, insulation and completion stages.
Frequently asked questions
How much does a garage conversion cost in the West Midlands?
Between £12,000 and £30,000 in 2026. A single integral garage converted to a habitable room typically costs £14,000 to £20,000. Adding a shower room takes it to £18,000–£25,000, and a detached garage converted to an office or annexe runs £25,000–£40,000.
Do I need planning permission for a garage conversion?
Usually not — an internal conversion is normally permitted development. Exceptions include estates with a planning condition requiring the garage to be kept as parking, flats and maisonettes, listed buildings, and some conservation areas. Significant changes to the external appearance can also require an application.
Do garage conversions need Building Regulations approval?
Yes, always. It is a material change of use, so Building Control approval is required regardless of whether planning permission is needed. It covers insulation, fire safety, ventilation, damp-proofing, structural work at the door opening and Part P certificated electrics. Without a completion certificate the conversion causes problems at resale.
How long does a garage conversion take?
Four to eight weeks on site for a standard single garage, closer to eight if a shower room is included. Allow another three to four weeks beforehand for drawings, any structural calculations and the Building Regulations submission.
Is a garage conversion cheaper than an extension?
Considerably. A garage conversion adds habitable space from around £12,000 because the walls, foundations and roof already exist. A single-storey extension of similar floor area starts around £45,000 because you are building all of that from scratch.
Will a garage conversion be cold?
Not if it is insulated properly. Garages are often single-skin brick with an uninsulated slab, so they need insulation to the floor, walls and ceiling. A converted garage typically has three external walls, so it is worth specifying above the Part L minimum and extending the central heating into the room rather than relying on an electric heater.