Floor build-up
Damp-proof membrane where required, insulation, screed or suitable floor build-up, and final finish.
Garage conversion cost guide · Hertfordshire
Garage Conversion Cost in Hertfordshire: 2026 Price Guide
A garage conversion can be a lower-cost way to create useful living space than building an extension, but the right budget depends on the garage type, its condition, the intended room and the compliance work required. This guide separates realistic benchmark bands from the scope that a written quote should confirm.
Updated 11 August 2026 · Prices are UK benchmark ranges, not a TCM quotation.
The short answer: budget by garage type before choosing finishes
Checkatrade’s May 2026 benchmark puts a typical 16m² integral or attached conversion at £10,000–£20,000, or roughly £625–£1,250 per m². Its figures assume a sound existing structure and basic fit-out; moving meter boxes, adding a kitchen or bathroom, cutting new openings and serious structural repairs sit outside that simple starting point. The Federation of Master Builders similarly stresses that size, purpose, location, garage style and finish level change the final price.
| Garage type | 2026 benchmark range | What typically changes the price |
|---|---|---|
| Integral single garage | £10,000–£14,000 | Usually the simplest route where the structure and services are already tied into the house. |
| Attached single garage | £10,000–£20,000 | Allow for the existing condition, a new front wall/window and any connection into the home. |
| Detached garage | £15,000–£25,000 | Service runs, insulation, security and access can add complexity. |
| Double garage (around 36m²) | £20,500–£45,000 | More area and layout flexibility; plumbing, structural changes and finish level drive the upper end. |
| Partial conversion | £5,500–£8,500 | A way to retain front-of-garage storage while creating a smaller room at the rear. |
Benchmark sources: Checkatrade, updated May 2026; Federation of Master Builders, updated February 2026. Both describe ballpark averages; a surveyed, written quotation is required for a project decision.
What a habitable-room conversion needs to account for
A garage is often structurally useful but thermally and technically different from the house. A credible budget breaks down the conversion scope rather than treating it as one undifferentiated figure.
Walls and roof
A survey-led insulation strategy for the existing construction; garages are rarely built to habitable-room thermal standards.
Former garage-door opening
Removal or retention strategy, new infill wall, window or door, and an exterior finish that works with the house.
Services
Electrical layout, heating and ventilation; add plumbing and drainage only where the intended use needs them.
Compliance
Building Regulations route, any structural design, fire separation and approval/sign-off allowances.
Planning permission and Building Regulations are separate checks
The Planning Portal states that planning permission is not usually needed where the work is internal and does not enlarge the building. That does not settle every project: a separate dwelling, a listed building, a conservation area, an Article 4 direction, a planning condition or new-development restrictions can change the answer.
Building Regulations remain relevant when a garage becomes habitable accommodation. The design and specification need to deal with the existing slab, wall and roof construction, ventilation, fire separation, electrical work and any structural alterations. Ask the party managing the conversion to identify the approval route and what completion evidence will be provided.
Illustrative planning pattern — not a TCM project record: before pricing an attached garage as a home office, a sensible feasibility sequence is to confirm whether permitted-development rights remain, inspect the floor and wall condition, define the insulation approach, identify the electrical/heating layout and decide whether the garage-door opening becomes a window or entrance. A kitchen, bathroom, annexe or structural opening into the house adds further design and compliance decisions.
How to compare garage conversion quotes fairly
- 1Confirm the assumed garage type, dimensions and intended use.
- 2Check whether floor damp-proofing, insulation and ventilation are included.
- 3Separate structural engineering, new openings and utility connections from the basic conversion allowance.
- 4Confirm Building Regulations, inspection fees, certification, VAT and exclusions in writing.
- 5Keep a proportionate contingency for concealed damp, slab-level or structural issues found after opening up.
- 6Compare finish assumptions: joinery, flooring, heating controls and decoration can make unlike quotes look similar.
Frequently asked questions
How much does a garage conversion cost in Hertfordshire?
A useful 2026 national benchmark is £10,000–£20,000 for a 16m² integral or attached garage. Detached garages commonly cost more because connecting services and upgrading the envelope can be more involved. South East labour and specification can move a local quotation above those benchmarks.
Do I need planning permission for a garage conversion?
Planning permission is not usually required where work is internal and does not enlarge the building. It can be needed for a separate dwelling, material external changes, listed buildings, conservation areas, new-estate restrictions or where permitted development rights have been removed. Confirm the position with the relevant local planning authority before work starts.
Do garage conversions need Building Regulations approval?
Yes. Turning a garage into habitable accommodation normally requires Building Regulations compliance. The design needs to address structure, insulation, ventilation, fire safety, electrics and the specific condition of the existing garage.
What makes a detached garage conversion more expensive?
A detached building can need longer runs for electricity, heating, water or drainage, as well as more work to improve insulation, security and access. The desired use matters too: a home office is usually less service-intensive than a kitchen, bathroom or annexe-style layout.
What should a garage conversion quote include?
Ask for the scope by element: survey assumptions, structural work, floor and insulation build-up, windows or infill wall, electrics, heating, ventilation, plumbing where relevant, finishes, Building Regulations, programme, VAT, exclusions and contingency. Compare like-for-like scopes rather than headline totals.
Plan the conversion before committing to a scope
Use the related pages below to check feasibility, planning and the next practical steps before requesting a surveyed quotation.