A garage conversion in 2026 costs between £8,000 and £25,000. A simple conversion (insulating, flooring, electrics, new front wall) costs £8,000–£15,000. A full conversion with plumbing, heating, and premium finishes costs £15,000–£25,000. It's the cheapest way to add a habitable room — no foundations, no roof, no planning permission in most cases.
Garage Conversion Costs at a Glance
Simple Conversion
Insulation, damp-proof membrane, new floor, electrics, plastering, new front wall with window. 2–3 weeks. Good for a home office or playroom.
Full Conversion with Utilities
Everything above plus plumbing, central heating extension, underfloor heating option, higher-spec finishes, and potentially a WC/shower room. 3–5 weeks.
Detached Garage Conversion
Extra insulation, service runs from the house, potentially new drainage connections. Works well as a home office, studio, or granny annexe. 3–6 weeks.
Double Garage Conversion
Converting both bays. Enough space for a large living room, bedroom with ensuite, or even a self-contained annexe. 4–6 weeks.
Partial Garage Conversion
Convert half, keep half for storage or parking. A partition wall divides the space. Popular when you still need some garage space. 2–3 weeks.
Garage to Bedroom with Ensuite
Full conversion with plumbing for ensuite shower room. Popular for downstairs bedroom/accessible living. 4–6 weeks.
Detailed Cost Breakdown
What Goes Into a Garage Conversion
A garage conversion is essentially about making an uninsulated, cold, damp box into a warm, dry, comfortable room. Here's where the money goes:
Replacing the garage door with a wall and window (£1,500–£3,500): The biggest visual change. You'll remove the roller or up-and-over door, build a blockwork wall with a DPC, fit a window (and potentially a door), render or brick-slip the exterior to match the house, and plaster internally.
Floor (£1,500–£4,000): Most garage floors are a thin concrete slab — too cold and often slightly lower than the house floor level. You'll typically lay a damp-proof membrane, rigid insulation (100mm Celotex or similar), and either a self-levelling screed or a floating chipboard floor. If the floor is significantly lower than the house, you may need to build it up, which adds cost.
Insulation (£1,000–£2,500): Walls need insulating — either internally with insulated plasterboard (cheaper, but you lose 50–75mm per wall) or with external wall insulation (more expensive but preserves internal space). The ceiling/roof needs insulation too — mineral wool between joists or insulated plasterboard.
Electrics (£800–£2,000): New consumer unit or spur from existing, lighting, sockets, switches, and a smoke alarm. If you're adding a lot of sockets or a dedicated circuit for a home office, costs rise.
Plastering (£700–£1,500): Walls and ceiling, ready for decoration. Over insulated plasterboard on walls and ceiling.
Heating (£500–£2,000): Extending your existing central heating with a radiator or two is cheapest (£500–£1,000). Electric underfloor heating is popular (£30–£50/m²). Water underfloor heating costs more (£60–£100/m²) but is cheaper to run.
Plumbing (£1,500–£4,000): Only needed if you're adding a WC, shower, or utility connections. Running waste pipes to the nearest drain and water supply from the house. Cost depends on distance and complexity.
Simple vs Full Conversion — What's the Difference?
A simple conversion (£8,000–£15,000) covers the essentials: new front wall, insulated floor, insulated walls, electrics, plastering. You get a dry, warm room ready for decoration. Ideal for a home office, playroom, or extra living space where you don't need water.
A full conversion (£15,000–£25,000) adds plumbing for a WC or shower room, central heating tied into your existing system, underfloor heating, higher-spec windows, and premium finishing. Suitable for a bedroom, self-contained annexe, or any room where you want water access.
Regional Pricing (Full Conversion)
What Affects the Price
Garage floor level
If the garage floor is significantly lower than the house floor (common — garages are often 50–150mm lower), you'll need to build it up with insulation and screed. A big step-down adds £500–£1,500.
Damp issues
Garages often lack a DPC (damp-proof course). If moisture is coming through the walls or floor, you'll need tanking, a new DPC, or cavity drain membrane. Budget £1,000–£3,000 for damp remediation.
Integral vs detached garage
Integral garages share walls with the house — they're warmer and services are closer. Detached garages need more insulation and longer service runs, adding £2,000–£5,000 to the cost.
Front wall specification
Replacing the garage door with a basic blockwork wall and window costs £1,500–£2,500. Matching brickwork (rather than render) or adding bi-fold doors costs £3,000–£5,000.
Adding plumbing
No plumbing = simple job. Adding a WC, shower, or utility sink means running water supply and waste pipes. If the nearest drain is far away, costs rise. Budget £1,500–£4,000 for plumbing.
Roof condition
If the garage roof is flat and in poor condition, it may need replacing. A new flat roof (EPDM or GRP) costs £2,000–£4,000 for a single garage. If the roof is fine, you just insulate from below.
External matching
Making the new front wall look like it was always part of the house. Brick slips: £40–£60/m². Full brick face: £80–£120/m². Render to match: £30–£50/m². Getting this right matters for property value.
Creating internal access
If the garage already opens into the house (integral), it's simple. If you need to knock through an external wall to create internal access, budget an extra £1,500–£3,000 for the opening, lintel, and making good.
How to Save Money on Your Garage Conversion
💡 Keep costs down without cutting corners
- Skip the plumbing if you don't need it. A home office or playroom doesn't need water. Omitting plumbing saves £1,500–£4,000.
- Use insulated plasterboard (dot-and-dab). Faster and cheaper than building a stud wall and insulating separately. Saves £500–£1,000 on a single garage.
- Electric panel heaters instead of central heating. If you're only using the room occasionally, electric heaters (£100–£300 each) avoid the cost of extending your central heating (£500–£1,000+).
- Do your own decoration. Get the builder to plaster and prime, then you paint and lay flooring. Saves £500–£1,500.
- Keep the garage door. If you want to maintain the option to revert, an insulated roller door (£800–£1,500) behind a stud wall lets you keep the original opening. But building a proper wall is better for insulation and building regs.
- Render rather than brick-slip the front wall. Render (£30–£50/m²) is cheaper than brick slips (£40–£60/m²) or matching brickwork (£80–£120/m²). If the rest of the house is rendered, it'll match perfectly.
- Use laminate instead of engineered wood flooring. Good laminate costs £15–£25/m² versus £40–£80/m² for engineered hardwood. Modern laminates are hard to distinguish from real wood.
What Should Be in a Builder's Quote
- Removal of garage door — disposal and making good the frame
- New front wall — blockwork, DPC, window, external finish (render/brick slips)
- Floor — DPM, insulation, screed or floating floor
- Wall insulation — insulated plasterboard or stud wall with mineral wool
- Ceiling insulation — between joists or insulated plasterboard
- Electrics — new circuit or spur, lighting, sockets, smoke alarm
- Plastering — walls and ceiling, ready for decoration
- Heating — radiator, electric heater, or UFH (should be specified)
- Plumbing — if applicable (WC, shower, utility connections)
- Internal access — if knocking through to the house, include lintel, structural support, and making good
- Waste removal — old garage door, rubble, skip hire
Common exclusions: Decoration, flooring, building regulations fees, and any external landscaping (new driveway surface where the garage apron was). Check the quote carefully.
Hidden Costs to Budget For
Building Regulations
Required for all garage conversions. Covers insulation, structural adequacy, fire safety, damp-proofing, and electrics compliance.
Driveway Making Good
The area where the garage door was may need a new surface — especially if you've changed the threshold level. A small patio or path section.
Boiler Capacity
Adding radiators to a new room may exceed your boiler's capacity. If your boiler is already on its limits, a replacement costs £2,500–£4,500.
Decorating & Flooring
Often excluded from builder's quotes. Paint (£100–£300), flooring (£15–£80/m²), and skirting boards (£150–£400).
Alternative Parking
Losing garage parking? You may need to create a driveway parking space or drop kerb (£1,000–£2,500 for the kerb crossing application and work).
Alternative Storage
Where will the stuff from your garage go? A garden shed (£300–£1,000) or external storage unit. Factor this in before you start.
Frequently Asked Questions
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