Garage Conversion Cost UK 2026: What to Budget

Full cost breakdown by conversion type, spec level and region — including what most quotes leave out

Buildcostr.ai · July 2026 · 7 min read

How much does a garage conversion cost?

A basic single garage conversion in the UK costs between £10,000 and £20,000 in 2026. A higher-spec conversion — fully insulated, plastered, heated, with new electrics and a bathroom — runs £20,000 to £35,000. The wide range reflects the enormous variation in what "garage conversion" means in practice.

Garage conversions are one of the most cost-effective ways to add usable space to a home. You already have the footprint, the roof and the walls — you are essentially fitting out an existing structure rather than building from scratch.

Cost breakdown by element

Here is a typical cost breakdown for a single garage conversion (approximately 15–20m²) in the UK:

Types of garage conversion

Integral garage conversion

The most straightforward type. An integral garage is already attached to and part of the house — it typically shares the same roof, floor level and party walls. These conversions generally require the least structural work and therefore sit toward the lower end of the cost range: £10,000–£20,000 for a standard fit-out.

Attached garage conversion

An attached garage is connected to the house but may have a separate roof and slightly different floor level. Conversions here often require a step down or up from the main house to be addressed, and the roof may need additional insulation or structural work. Budget £12,000–£25,000.

Detached garage conversion

The most complex and expensive type. A detached garage requires new services runs (electricity, heating, drainage if adding a bathroom) from the main house. The result — a standalone studio, home office or annex — is highly desirable, but costs reflect the additional work: £20,000–£40,000 or more depending on specification.

Double garage conversion

Double garages (typically 35–50m²) cost proportionally more but offer significantly more floor area. A well-specified double garage conversion can create an open-plan kitchen-diner, a large home office or a two-room annex. Budget £25,000–£55,000 for a high-spec double conversion.

The garage door question

One of the biggest decisions — and cost variables — in a garage conversion is what to do with the existing opening. Your main options are:

• Brick up the opening with a window and new external finish — the most thermally efficient option, typically £2,500–£5,000
• Full-height glazing with bi-fold or sliding doors — highly desirable for garden rooms or living spaces, £5,000–£12,000
• Retain the garage door and insulate it — the cheapest option but least thermally efficient, suitable for workshops or utility rooms, £500–£2,000

The choice significantly affects the kerb appeal of the finished conversion and how it reads from the street. For properties where external appearance matters — conservation areas, terraced streets, smart suburban roads — the quality of the new facade deserves serious budget consideration.

Planning permission and building regulations

Most single domestic garage conversions in England do not require planning permission under permitted development rights, as you are not changing the external footprint of the building. However, several situations do require a planning application:

• Properties in conservation areas or national parks
• Listed buildings (where listed building consent is always required)
• New-build properties where the planning condition requires the garage to remain as a garage
• Detached garage conversions that create a separate dwelling (these need a change of use application)

Building regulations approval is required for all garage conversions regardless of planning. This covers structural integrity, fire safety, insulation standards, ventilation and electrics. Budget £600–£1,200 for building regulations fees and allow for inspections at key stages.

Does a garage conversion add value?

In most cases, yes — but the extent depends on what you're gaining and what you're losing. A garage conversion that creates an extra bedroom or a high-quality home office typically adds 5–10% to a property's value.

The caveat: in areas where off-street parking is scarce and highly valued, losing a garage can reduce the property's appeal to certain buyers. If parking is a significant factor in your area, consider whether a tandem driveway space or carport can be created to mitigate this before committing to the conversion.

How long does a garage conversion take?

A straightforward single garage conversion with a competent small builder typically takes 3–5 weeks on site. More complex projects — adding a bathroom, significant structural works, or a high-spec finish — can take 6–10 weeks. Detached conversions that require new service runs tend to add 1–2 weeks to the programme.

Getting an accurate quote for your garage conversion

Garage conversions are frequently underquoted. Builders omit insulation upgrades, forget building regulations fees, exclude VAT or underestimate the electrical works involved. The result is a project that starts at one number and finishes at a significantly higher one.

An independent cost plan before you go to tender protects you. Buildcostr.ai produces a full, itemised cost plan from your architectural drawings in 30 minutes — covering every element of the conversion so you can evaluate builder quotes with confidence. See a sample report or order yours from £99.

Thinking about extending instead? Read our guide to house extension costs in 2026 or compare single vs double storey extension costs.