Garage Conversion Guide: Cost, Planning & Design 2026
A garage conversion is one of the most affordable ways to add a room to your home. Since the shell already exists, you are essentially fitting out an existing space rather than building from scratch. It is ideal for a home office, playroom, extra bedroom, or gym.
What you need to know
What is involved?
A garage conversion typically involves: replacing the garage door with a wall and window, insulating the walls, floor, and ceiling to Building Regulations standard, damp-proofing the floor, adding heating, electrics, and plumbing (if needed), and finishing to match the rest of the house.
Single vs integral garages
Integral garages (attached to and under the main roof) are simpler to convert because they share walls and often a ceiling with the house. Detached garages require more work (and may need planning permission) but can become independent spaces like a home office or annexe.
Common uses
The most popular conversions are: home office (especially post-pandemic), additional bedroom with en-suite, playroom or family room, gym or hobby room, and downstairs bedroom for accessibility. The right use depends on your family needs and how it affects parking.
How much does it cost?
| Item | Typical Cost Range |
|---|---|
| Basic conversion (single garage) | £15,000–£25,000 |
| High-spec conversion with en-suite | £25,000–£40,000 |
| Double garage conversion | £25,000–£45,000 |
| Detached garage conversion | £20,000–£40,000 |
| Professional fees | £1,500–£3,000 |
| Heating installation | £1,000–£3,000 |
Prices based on Dorset rates, 2026
Planning permission
Most integral garage conversions fall under Permitted Development. You are changing the use of an existing part of the house, not building anything new. However, if your property has a condition removing PD rights (common on newer builds), or if you are in a conservation area, planning permission may be needed.
Converting an integral garage is usually considered an internal alteration and does not require planning permission. Replacing the garage door with a matching wall and window is also typically PD. However, check for conditions on your original planning permission that may restrict changes.
Building regulations
Building Regulations approval is required. Key requirements: floor insulation and damp-proofing (the garage floor is likely below the level of the house), wall insulation, adequate heating, ventilation, fire safety (fire door if the garage opens into the house), and structural adequacy of any new openings.
Typical timeline
| Phase | Duration |
|---|---|
| Design | 1–2 weeks |
| Building Regulations | 2 weeks |
| Build | 4–8 weeks |
Frequently asked questions
Ready to get started?
Professional design plans for your project. Fixed-price, no obligation.
Every plan drawn by qualified drafters in Poole, Dorset
Serving homeowners across Poole, Bournemouth, Christchurch, Wimborne, Wareham, and the wider Dorset area.