Introduction
Converting a garage into living space is one of the most cost-effective ways to add a room to your home without the disruption of a full extension. Whether you want an extra bedroom, a home office, a playroom or a self-contained annexe, a garage conversion makes use of a structure that is already there, saving significantly on foundations, walls and roofing.
But how much should you budget for a garage conversion in 2026? The answer depends on a range of factors including the size of the garage, the condition of the existing structure, the specification of finishes and your location within the UK. In this guide, we break down the typical costs for single and double garage conversions, explain what affects the price and help you plan a realistic budget.
If you are a homeowner or self-builder planning a conversion project, having a detailed estimate prepared before you start is the best way to avoid surprises and keep your budget on track.
Why Convert Your Garage?
Garage conversions are popular for good reason. They are typically cheaper per square metre than building an extension, they usually fall within permitted development rights, and they cause less disruption than major structural work. For many households, the garage is underused storage space that could deliver far more value as habitable accommodation.
Common uses for converted garages include home offices, guest bedrooms, utility rooms, gyms, playrooms and self-contained annexes for elderly relatives. The right conversion can add genuine value to your property while improving your quality of life.
Single Garage Conversion Costs
A standard single garage measures approximately 6m x 3m, giving you around 18 square metres of additional floor space. The cost of converting a single garage typically ranges from £8,000 to £18,000, depending on the specification and condition of the existing structure.
| Work Element | Typical Cost Range |
|---|---|
| Floor insulation and levelling | £1,200 – £3,000 |
| Wall insulation and plastering | £1,000 – £2,500 |
| Garage door removal and new wall | £1,500 – £3,000 |
| Window and door installation | £800 – £2,000 |
| Electrics (lighting, sockets, consumer unit) | £1,200 – £2,500 |
| Heating (radiator or underfloor) | £600 – £1,800 |
| Decoration and finishes | £800 – £2,000 |
These figures assume a straightforward conversion where the existing garage structure is in reasonable condition. If the floor needs to be lowered or the damp-proof course replaced, costs will increase accordingly.
Key Point: The garage door opening represents the biggest single element of cost. Replacing it with a fully insulated brick wall, window and external door typically accounts for 15 to 20 per cent of the total project cost.
Double Garage Conversion Costs
A double garage offers around 30 to 36 square metres of floor space, making it large enough for a substantial living area, a bedroom with en-suite or even a small self-contained flat. Costs for a double garage conversion typically range from £15,000 to £30,000.
The per-square-metre cost is usually slightly lower than a single garage conversion because the fixed costs, such as building regulations fees and professional fees, are spread across a larger area. However, a double garage conversion may require additional structural work if you are creating partition walls, installing plumbing for a bathroom or kitchen, or adding separate heating zones.
If you plan to convert a double garage into a self-contained annexe with its own kitchen and bathroom, expect to budget towards the upper end of the range or beyond, as plumbing and drainage work adds significantly to the cost.
What Affects the Price?
Several factors will influence the final cost of your garage conversion:
- Condition of the existing structure – damp issues, subsidence or a poor-quality roof will add to costs
- Floor level differences – if the garage floor is significantly lower than the house, it may need raising or stepping
- Specification of finishes – budget fittings versus high-end materials make a significant difference
- Plumbing requirements – adding a bathroom, shower room or kitchenette increases costs considerably
- Structural alterations – removing or modifying load-bearing walls, adding steel beams or installing new lintels
- Location – labour and material costs vary across the UK, with London and the South East typically 15 to 25 per cent higher than the national average
Building Regulations and Planning Permission
Almost all garage conversions require building regulations approval, even if they do not need planning permission. Building regulations ensure that the conversion meets minimum standards for structural stability, thermal insulation, fire safety, ventilation, damp proofing and electrical safety.
You will need to submit a building regulations application to your local authority, which costs between £200 and £500 depending on the scope of work and the local authority’s fee schedule. An approved inspector can also be used as an alternative to local authority building control.
When Planning Permission Is Required
Most garage conversions fall under permitted development and do not require planning permission, provided you are converting an integral or attached garage and the external appearance of the building does not change significantly. However, you will need planning permission if:
- Your property is in a conservation area, Area of Outstanding Natural Beauty or National Park
- The property is a listed building
- Previous permitted development rights have been removed by planning condition
- The conversion involves a significant change to the external appearance
If you are unsure whether your project needs planning permission, check with your local planning authority before starting work. A planning drawing estimate can help you understand the costs involved if an application is required.
Common Additional Costs
When budgeting for a garage conversion, it is important to account for costs that are often overlooked:
- Building regulations fees – £200 to £500
- Structural engineer – £300 to £700 for calculations and drawings
- Architect or designer – £500 to £1,500 for design drawings
- Skip hire and waste removal – £200 to £500
- Drainage alterations – £500 to £2,000 if adding a bathroom
- Alternative parking provision – creating a new driveway or hardstanding if required
A contingency allowance of 10 to 15 per cent on top of your estimated build cost is advisable to cover any unexpected issues that arise during the conversion, such as hidden damp or structural defects that only become apparent once the work starts.
Getting an Accurate Garage Conversion Estimate
The cost ranges in this guide provide a useful starting point, but every garage conversion is different. The best way to establish a realistic budget for your project is to have a professional estimate prepared from your specific plans and drawings.
At First4Estimating, our qualified Quantity Surveyors can prepare a detailed budget estimate for your garage conversion that covers every element of the work, from structural alterations through to decoration and finishes. This gives you a clear picture of costs before you start, helps you compare quotes from builders and ensures you are not caught out by unexpected expenses.
Ready to find out what your garage conversion will cost? Send us your plans and we will provide a detailed estimate within five working days.