Garage conversion cost in London and Essex (2026)
A garage conversion typically costs between £13,000 and £50,000 in London and Essex in 2026. It is the cheapest way to add a proper room to a house, and the reason is structural rather than clever: the walls, the floor and the roof already exist. You are not paying for foundations. You are not paying for a new roof. That alone puts a garage conversion 60 to 70 percent below a single storey extension of the same floor area.
The catch is that garages were never built to be lived in. Almost every pound you spend goes on bringing an unheated, often damp, single-skin structure up to a standard where Building Control will sign it off as habitable space.
This guide covers what that actually costs in 2026, broken down by garage size and intended use. We convert garages across North London, Brentwood, Chingford and Essex, so these figures sit 15 to 25 percent above national averages, which is the real London and South East picture.
Garage conversion cost by size
| Garage and use | Floor area | Typical London and Essex cost | Cost per square metre |
|---|---|---|---|
| Single, dry room (office or bedroom) | 15 to 18 m² | £13,000 to £20,000 | £1,000 to £1,200 |
| Single, with plumbing (kitchen or bathroom) | 15 to 18 m² | £18,000 to £26,000 | £1,200 to £1,500 |
| Double, dry room | 30 to 36 m² | £24,000 to £36,000 | £900 to £1,100 |
| Double, high spec or wet room | 30 to 36 m² | £36,000 to £50,000 | £1,400 to £1,900 |
Standard integral or attached garages sit at the lower end. Detached garages cost more because all four walls and the roof need a full thermal upgrade.
Integral, attached or detached: why your garage type sets the price
This is the first question worth answering, because it moves the number more than anything else on the list.
An integral garage sits inside the footprint of the house, with living space above it and heated rooms on two or three sides. It is the cheapest conversion available. The surrounding structure is already insulated, the heating system is a few metres away, and forming a doorway into the hall is usually straightforward.
An attached garage shares one wall with the house. You have one warm side and two or three cold external walls to insulate, plus a roof that was probably never insulated at all.
A detached garage stands alone. Every wall is external, the roof is external, the floor sits on unheated ground, and there is no heating or drainage nearby. Running services across the garden is its own line item. A detached conversion can cost 40 to 50 percent more than an integral one for exactly the same floor area, and homeowners are often surprised by that.
What moves the number
Condition of the structure. Many garages are built single-skin, meaning one course of brick with no cavity. That cannot be insulated to standard as it stands, so a new internal blockwork or timber leaf goes up inside the existing wall. You lose around 100mm of floor width on each treated wall.
The floor. Garage floors usually sit 100 to 150mm below the house floor level and often have no damp proof membrane. Raising and tanking the floor to match the house is standard work on most conversions and is rarely optional.
Intended use. A dry room such as an office or bedroom is the cheapest outcome. A kitchen or bathroom adds £3,600 to £7,200 for plumbing and drainage, and considerably more if the garage sits far from your existing soil stack.
The front wall. Removing the garage door, fitting a new lintel and building an insulated wall with a window is the single biggest structural cost on most conversions. Getting the new window proportioned so the front of the house does not look like a filled-in garage is worth the extra design attention.
Insulation and heating. Walls, floor and roof all need insulating, and the space needs a heat source. If your existing boiler cannot carry another radiator circuit, replacing it adds £1,500 to £3,500.
Opening into the house. Forming a new opening in a load-bearing wall between the garage and the hall or kitchen needs a lintel and structural calculations.
What is included in a garage conversion quote
A standard quote covers removing the garage door, the new front wall and window, insulation to the walls, floor and roof, damp proofing, electrics, heating, plastering, flooring and decoration.
Sitting on top of that: Building Control at £360 to £1,200, architectural drawings at £240 to £600, wet-room plumbing where needed, a replacement boiler if the heating cannot reach the space, and VAT.
Garage conversions produce fewer nasty surprises than loft conversions or extensions, because the structure is visible from day one. The exception is the floor. Until it is broken out, nobody can tell you with certainty what is underneath it.
Planning, Building Regulations and the parking condition
Most garage conversions fall under Permitted Development because the footprint of the building does not change. That covers the majority of houses in London and Essex.
Building Regulations approval is a different matter and is nearly always required. Building Control will look at thermal performance in the walls, floor and roof, fire safety and escape, ventilation, electrical work and structural changes around the old door opening. Do not skip this. An unsigned conversion shows up in the conveyancing search when you sell, and the buyer's solicitor will ask for an indemnity policy or a retention.
One trap worth checking early: on newer estates, and on some flats and maisonettes, a planning condition requires the garage to remain available for parking. That condition survives the sale of the house. Look at the original planning permission for the estate before you commit to anything, because reversing a completed conversion is expensive.
Is a garage conversion worth doing?
On cost per square metre of new living space, nothing else comes close. It is quick as well, with most jobs done in two to four weeks, and it causes far less disruption than an extension because the work happens outside the main body of the house.
The honest trade-off is parking. In parts of London where a driveway or off-street space carries real value at resale, giving it up can cancel out some of the gain. Most garages in London are too narrow for a modern car and are used for storage instead, in which case there is nothing much to lose. Worth ten minutes of thought before you start, and worth asking a local agent rather than guessing.
Garage conversion cost: frequently asked questions
How much does it cost to convert a single garage?
Between £13,000 and £20,000 for a standard single garage used as a dry room in London and Essex in 2026. Adding a bathroom or kitchen raises this to £18,000 to £26,000.
How much does a double garage conversion cost?
Between £24,000 and £36,000 for a standard double garage, rising to around £50,000 for a high-spec conversion with plumbing.
Is a garage conversion cheaper than an extension?
Yes, typically 60 to 70 percent cheaper, because there are no new foundations or roof to build.
Do I need planning permission to convert my garage?
Usually not, as the footprint does not change, but you will need Building Regulations approval. Check for any estate planning conditions on newer homes.
How long does a garage conversion take?
Most take 2 to 4 weeks. More complex jobs with plumbing or structural changes can take 6 to 8 weeks.
Thinking of converting your garage in London or Essex?
Mammoth Builds gives you a clear fixed price and handles the structure, insulation, Building Regulations and finish. Get your free quote today.
