Garage conversion cost in Basingstoke ranges from around £9,000 for a basic single garage room to £36,000 for a fully fitted double garage annexe with plumbing. Unlike a loft conversion, where roof structure drives most of the variation, a garage conversion’s cost is decided mainly by what you want the room to do — a home office costs less than a bedroom, and a bedroom costs less than a room with a shower. This guide sets out realistic 2026 figures for the Basingstoke area and what actually moves them.
Garage Conversion Costs by Type in Basingstoke
These are realistic 2026 ranges locally, covering the structural and fit-out work involved. They exclude furniture and any work to the rest of the house.
- Single garage, basic room: £9,000 to £14,000
- Single garage, home office: £9,500 to £14,000, reflecting the additional electrical first fix
- Single garage, bedroom: £11,000 to £16,000, reflecting the escape window and fire door work
- Single garage with en suite: £16,000 to £22,000, or £19,000 to £26,000 as a bedroom with en suite
- Double garage, single open room: £16,000 to £24,000
- Double garage, partitioned into two rooms: £18,000 to £28,000
- Double garage annexe with kitchenette and shower: £26,000 to £36,000
- Partial conversion, room plus retained utility area: £10,000 to £15,000
What Actually Drives the Price
What the room is for
This matters more on a garage conversion than almost any other type of building project, because the shell is already there and the cost is almost entirely in the fit-out. A basic room needs insulation, a floor, plastering and minimal electrics. A bedroom adds an escape window and possibly a fire door. A room with plumbing adds several thousand pounds for drainage that usually has to be run some distance to connect to the existing system.
Integral versus detached
Most Basingstoke garages are integral, built as part of the main house, which keeps costs down because services, the roof and at least one wall are already shared with the house. In Overton and some of the older parts of the district, detached garages are more common, and converting one means treating it as a small standalone building — its own foundations, its own connection to services, sometimes its own planning consideration. Expect £2,000 to £5,000 more on a comparable detached conversion.
Damp proofing the slab
Almost every garage floor was built without a damp proof membrane to modern standards, since garages were never meant to be heated, dry spaces. Bringing the slab up to standard — typically a new damp proof membrane and insulated floor build-up over the existing concrete — is close to unavoidable and adds £1,500 to £3,000 depending on the floor area.
Fire safety for bedrooms
A bedroom needs a suitable escape window and, where the room sits on an escape route through the house, a fire door with self-closer. This is rarely expensive in isolation, but it is a specific design requirement that a home office or playroom does not carry, and it needs planning in from the start.
Age of the property
Newer garages, particularly on Chineham and Hook’s later development phases, tend to start from a better thermal position and need less remedial work to the shell. Older garages on 1960s and 70s stock, and older still on Tadley’s more variable post-war construction, sometimes need more investigation before a firm price can be given.
Access
Most Basingstoke estate properties have straightforward driveway access. Overton’s historic core and some of Old Basing’s older lanes are the exception, where narrow streets and limited parking can add £500 to £1,500 for materials handling.
Three Worked Examples
A 1970s single garage in South Ham, converted to a home office. Standard integral construction, good access, straightforward electrical first fix for a desk, monitor and printer setup. Around £11,500.
A double garage in Hatch Warren, split into a home office and a playroom. Later 1980s construction with reasonable existing insulation, dividing wall built to separate the two spaces, each with its own electrical circuit. Around £21,000.
A detached garage on an older Overton property, converted to a bedroom with en suite. Standalone structure needing its own foundation check and a longer drainage run back to the house, plus escape window and fire safety design. Around £27,000, toward the upper end because of the detached construction and plumbing combined.
Costs That Are Easy to Forget
- Building Regulations fees: £300 to £600 for a typical garage conversion, less than a loft conversion because the scope is usually smaller
- Damp survey: £150 to £300 if the slab condition is uncertain and needs professional assessment before design
- Structural engineer: £400 to £800 where the roof or a partition wall needs calculations, more common on double garage splits
- Planning application: £258 where one is needed, typically only for larger external alterations or detached structures in conservation areas
- Redecoration nearby: the hallway or landing adjoining the converted space sometimes needs minor making good
Does a Garage Conversion Add Value in Basingstoke?
A garage conversion typically adds meaningfully more value than it costs, particularly where it takes a house from three bedrooms to four, since four-bedroom stock commands a real premium over three-bedroom across most of the district. Unlike a loft conversion, a garage conversion is usually the cheapest way to add a bedroom, because there is no roof structure to alter and no staircase to build.
The trade-off worth weighing is parking. Losing a garage that is actually used for a car, rather than storage, can mildly affect buyer appeal on some streets, though this rarely outweighs the value of an additional bedroom or living space. Properties with a driveway in front of the garage, which describes most of Basingstoke’s estate housing, are least affected, since off-street parking remains available regardless.
How Long Does It Take?
- Single garage, basic room or office: two to four weeks
- Single garage, bedroom: three to five weeks
- Single garage with en suite: five to seven weeks
- Double garage, single room: four to six weeks
- Double garage, partitioned or with plumbing: six to eight weeks
Add one to two weeks beforehand for Building Regulations submission, longer if a structural engineer or planning application is involved.
Paying for It
Garage conversions are normally paid in staged payments tied to milestones rather than a deposit and a final bill: a modest deposit for materials, then payments at completion of structural work, first fix, and completion.
Treat a request for a large sum up front as a warning sign. A deposit covering initial materials is reasonable. A demand for thirty or forty per cent before work starts is not, and it remains the single most common precursor to trouble in domestic building work regardless of project size.
Comparing Quotes Properly
Ask whether the contractor has actually been in the garage and checked the slab for damp. A figure given over the phone or from a photograph is a guess, and the guess almost always moves once the floor is properly assessed.
Then check that damp proofing, insulation, Building Regulations submission and making good are all inside the quoted figure rather than sitting outside it as provisional sums. A quote that looks a few thousand pounds cheaper but excludes damp proofing the slab is not actually cheaper.
Structural requirements for insulation, damp proofing and fire escape in converted garages are set out by LABC.
For a figure specific to your property, we survey the garage and issue a fixed written quotation. It is worth reading what a single garage conversion involves, or comparing it against a double garage conversion if you have more space to work with.