Garage Conversion Cost UK 2026

How much does a garage conversion cost? Single and double garage prices with a detailed breakdown of insulation, new front wall, flooring, electrics, plumbing, and finishing.

Last updated: April 2026

A garage conversion is one of the most cost-effective ways to add usable living space to a UK home. Most garages are too small for modern cars, used primarily for storage, and represent a significant volume of wasted space that can be transformed into a bedroom, home office, playroom, gym, or self-contained annex for a fraction of the cost of an extension.

This guide covers the realistic 2026 cost of garage conversions across the UK, including integral (attached) garages, detached garages, and double garages. Whether you are a homeowner planning a conversion or a builder pricing a job, these figures provide a reliable benchmark for all the key elements of the work.

Summary Cost Table

Prices include all structural work, insulation, electrics, plastering, flooring, and decoration. London and the South East are typically 15–25% higher than the national average. Scotland, Wales, and the North of England sit at the lower end of each range.

Detailed Cost Breakdown

New Front Wall

The garage door opening must be replaced with an insulated wall, window, and sometimes a new front door. This is the most visible element of the conversion and must match the existing property for building regulations and kerb appeal.

• Blockwork wall with cavity insulation — £1,000 – £2,000
• Window (UPVC double-glazed) — £300 – £600
• External door (if required) — £300 – £600
• Matching render, brick slip, or facing brick — £300 – £800
• Lintel for window/door opening — £100 – £200
• Total new front wall — £1,500 – £3,500

Matching the existing external finish is important both for aesthetics and planning compliance. If the house is brick, the new wall can use matching facing bricks or brick slips over blockwork. If rendered, the new wall is rendered to match. Most integral garage conversions do not require planning permission under permitted development, but the front wall must comply with building regulations for thermal performance and structural integrity.

Floor

Garage floors are typically 150mm lower than the main house floor and are uninsulated concrete. The floor must be raised, insulated, and finished to match the adjacent rooms.

• DPM (damp-proof membrane) — £3 – £5 per m²
• PIR insulation (Celotex/Kingspan, 75–100mm) — £8 – £15 per m²
• Self-levelling screed or timber joists — £15 – £30 per m²
• Finished flooring (carpet, LVT, laminate) — £15 – £40 per m²
• Total floor for single garage (~15 m²) — £1,000 – £2,500

The most common approach is to lay a DPM, PIR insulation boards, and then either a self-levelling compound or timber battens with chipboard decking. This brings the floor level up to match the house and provides the required thermal insulation. If the existing concrete slab is badly cracked or damp, additional remedial work may be needed.

Walls — Insulation and Dry Lining

Garage walls are typically single-skin brick or blockwork with no insulation. They must be insulated and dry-lined to meet current Building Regulations for thermal performance.

• Insulated plasterboard (PIR-backed, per m²) — £20 – £35
• Timber battens and mineral wool (alternative method) — £15 – £25 per m²
• Skim coat over plasterboard — £10 – £18 per m²
• Total wall insulation and finishing (single garage) — £1,200 – £2,500

Insulated plasterboard (Kingspan Kooltherm or Celotex PL4000) bonded directly to the existing walls is the fastest and most space-efficient method. It reduces room dimensions by approximately 40–60mm on each wall. The alternative — timber battens with mineral wool between — gives slightly better performance but takes up more space (75–100mm per wall).

Ceiling

• Plasterboard and skim (if ceiling joists exist) — £400 – £800
• New ceiling joists, insulation, plasterboard, and skim — £800 – £1,500
• Insulation (mineral wool, 270mm between joists) — £5 – £10 per m²

If the garage is integral (under a bedroom), the ceiling may already have joists in place. Detached garages typically have an open roof structure that needs new ceiling joists installed before insulation and plasterboard can be fitted.

Electrics

• New circuit from consumer unit — £200 – £400
• Sockets (6–8 double sockets) — £400 – £700
• Lighting circuit (downlights) — £300 – £500
• Heated towel rail circuit (if en-suite) — £100 – £200
• Total electrical (basic room) — £800 – £1,500

Plumbing and En-Suite

Adding an en-suite shower room or WC to a garage conversion is popular but adds significant cost due to the need for new drainage runs.

• En-suite (shower, basin, WC) — budget — £3,000 – £5,000
• En-suite — mid-range — £5,000 – £8,000
• New drainage run to soil stack or manhole — £500 – £1,200
• Hot and cold water supply — £300 – £600
• Radiator or underfloor heating — £300 – £800

Heating

The converted garage must be heated to the same standard as the rest of the house. The simplest option is extending the existing central heating system.

• New radiator (teed off existing system) — £200 – £400
• Electric underfloor heating (per m²) — £30 – £50
• Wet underfloor heating (per m²) — £50 – £80
• Electric panel heater (wall-mounted) — £100 – £250

For integral garages, extending the existing central heating with a new radiator is the cheapest and most effective option. Detached garages may require a longer pipe run from the house, adding cost. Electric underfloor heating is a popular alternative for detached garages because it avoids the need for pipe runs across the garden.

Plastering and Decoration

• Skim coat (all walls and ceiling) — £500 – £1,000
• Painting (2 coats emulsion, walls and ceiling) — £300 – £600
• Skirting boards and architraves — £150 – £300
• Internal door (connecting to house) — £150 – £300

Fire Safety

Building Regulations require specific fire protection measures when converting an integral garage, because the garage previously served as a fire barrier between the house and vehicles/fuel.

• 30-minute fire door (FD30, between garage and house) — £150 – £300
• Fire-rated plasterboard (if required) — £3 – £5 per m² above standard board
• Smoke detectors (interconnected, all floors) — £150 – £300

Factors That Affect Cost

• Garage type — integral garages are cheaper to convert because they share walls with the house and have existing services nearby. Detached garages need more work on electrics, plumbing, heating, and drainage.
• Intended use — a simple bedroom or office is the cheapest conversion. Adding an en-suite, kitchenette, or full bathroom significantly increases cost due to plumbing and drainage.
• Floor condition — if the existing concrete slab is badly cracked, damp, or significantly below house floor level, remedial work adds £500–£1,500.
• Roof condition — if the garage roof needs replacing (common with flat-roofed garages), add £1,500–£4,000 for a new EPDM or GRP roof.
• Structural opening — if you want to open the garage into the house (removing the dividing wall), structural work with an RSJ adds £1,500–£3,500.
• Location — London and the South East are 15–25% above the national average.

How Long Does It Take?

These timescales cover the full build from new front wall to final decoration. A basic conversion with no plumbing is one of the fastest home improvement projects. Adding an en-suite or kitchenette extends the timeline due to drainage work and tiling. Building control inspections are required at key stages — foundations (if applicable), damp-proofing, insulation, and completion.

How to Save Money

• Keep it simple — a basic bedroom or office conversion without plumbing is the cheapest option at £8,000–£15,000. Adding an en-suite doubles the plumbing and drainage cost.
• Use the existing structure — if the garage walls, roof, and slab are sound, you avoid structural remedial work. Get a builder to inspect before committing.
• DIY the decoration — painting, laying carpet or LVT, and fitting skirting boards are straightforward DIY tasks that save £500–£1,000 in labour.
• Choose electric heating — extending the central heating system to a detached garage can be expensive due to long pipe runs. Electric underfloor heating or panel heaters are cheaper to install (though more expensive to run).
• Get multiple quotes — garage conversion prices vary widely between builders. Get at least three itemised quotes and ensure they include building regulations fees.
• Apply for council tax exemption — a garage conversion that does not add a self-contained dwelling does not usually increase your council tax band. However, a self-contained annex may be assessed separately.

Common Questions