Garage Conversion London
The cheapest square metre you can add to a London house, provided the floor, the damp proofing and the insulation are done properly rather than skipped.
- Garage conversion: £10,000 to £25,000+
- Rated 4.9 from 31 reviews on MyBuilder
- Free site survey, itemised quote
A garage conversion is the cheapest square metre you will ever add to a London house, because the roof, the foundations and three of the four walls already exist. What you are really buying is a floor that meets current standards, a wall where the door used to be, insulation, and the services to make the room usable.
It is also the conversion most often done badly. An integral garage was built as an unheated, unventilated store with a floor below the level of the house and no damp proofing worth the name. Turning that into a habitable room means dealing with all four of those things, and skipping any one of them produces a cold room that smells of damp within a year.
What does a garage conversion cost in London?
| Conversion | Typical London cost | Time on site |
|---|---|---|
| Single garage, simple room | £10,000 to £15,000 | 3 to 4 weeks |
| Single garage with plumbing, office or shower room | £15,000 to £20,000 | 4 to 5 weeks |
| Double garage or high specification | £20,000 to £25,000+ | 5 to 7 weeks |
| Detached garage, converted and serviced | £15,000 to £28,000 | 5 to 8 weeks |
The element breakdown is where the variation lives, and it is worth seeing which of these your quote includes.
| Element | Typical cost | Notes |
|---|---|---|
| Infilling the garage door with a wall and window | £1,000 to £1,500 | Cavity wall built off a new foundation or thickened slab |
| Supporting beam or lintel over a wide opening | £750 to £1,500 | Needed where the opening is wide or only partly infilled |
| Damp proofing and wall insulation | £500 to £1,000 | Membrane, battens or insulated board |
| Raising and insulating the floor | £1,000 to £2,500 | Garage slabs usually sit below the house floor level |
| Electrics, heating and second fix | £1,500 to £3,500 | New circuits certified by a registered electrician under Part P, radiator or underfloor |
Our London garage conversion cost guide breaks the figures down further, and which renovations add the most value is worth reading before you commit, because losing off-street parking is not free in every London postcode.
Do you need planning permission?
Usually not for an integral garage, because converting the inside of an existing building generally falls within permitted development, provided the work is internal and the external appearance does not change materially. Infilling the garage door does change the appearance, which is where the caveats begin.
- Permitted development can be removed by an Article 4 direction, and on some estates a condition on the original planning permission removes the right to convert the garage, so check both
- Flats and maisonettes have no householder permitted development rights
- A detached garage converted to habitable use is more likely to need permission than an integral one
- Some estates carry a planning condition or a covenant requiring the parking space to be retained, which is separate from planning permission and binds you anyway
- Building regulations apply in every case, whether or not planning does
Check the title deeds as well as the planning position. A covenant requiring a parking space to be kept is enforceable by whoever holds the benefit of it, and it does not disappear because the council raises no objection. Our permitted development guide covers the planning side.
What building regulations actually require
This is where a garage conversion is won or lost, because a garage was never built to any of these standards.
- Part C, a floor with a damp proof membrane linked to the wall damp proof course, since a garage slab usually has neither
- Part L, insulation to the floor, the walls and the ceiling or roof, which is what turns an unheated store into a room that can be warmed
- Part F, background and purge ventilation, plus extraction where a shower room or utility is formed
- Part B, fire separation where the garage adjoins the house, and a compliant escape window where the room is a bedroom
- Part P, new circuits certified by a registered electrician or notified to building control, since every one of these needs them
- Structural support over the old door opening, sized by a structural engineer where the opening is wide or only partly infilled
The floor is the item most often skimped. A garage slab typically sits a step below the house floor and has no membrane, so it has to be raised, insulated and tanked to arrive level with the rest of the ground floor. Doing that properly is a significant part of the cost and the reason the cheapest quote is usually the one that has not allowed for it. Our building regulations guide sets out the inspection stages.
Is it worth doing?
It depends on what the parking is worth where you live, and that is a genuinely local question rather than a general one. In outer boroughs with unrestricted street parking, converting a garage almost always adds more value than the space it removes. In a controlled parking zone where a resident permit is hard to come by, or on a street where off-street parking is priced into the asking figure, the arithmetic can go the other way.
The honest test is whether you actually park a car in it. Most London garages built before about 1980 are too narrow for a modern car anyway and are used as storage, in which case the conversion is converting a shed into a room and the answer is usually yes.
How we run a garage conversion
We carry out the whole conversion with our own team: the floor raised, insulated and tied into the damp proof course, the door opening infilled on a proper foundation, the walls and ceiling insulated, and the electrics, heating and decoration finished. Where the opening is wide or only part infilled, the structural engineer we appoint sizes the beam or lintel and we install it. We make the building regulations application and book the inspections, and building control issues the completion certificate at the end. If the garage turns out to be the wrong answer, the house extensions page and the side return page cover the alternatives, and a garage conversion inside a wider refit is covered on our whole-house renovation page.
I am very happy to recommend George after he completed the work on my 2 bathrooms. He worked very hard to make sure everything was completed and even came on a Sunday evening to finish the work...which shows how committed he is to…
George was very friendly and helpful from start to finish. He worked really hard to ensure our kitchen was installed to a high standard and was accommodating to the changes we wanted along the way. We're really happy with the end result…
George always kept to commitments and arrived on time. He offered helpful suggestions during his initial visit and promptly provided a reasonably priced quote. The work started on time and George worked really hard every day. There were…
FAQ
Frequently Asked Questions
How much does a garage conversion cost in London?
A single garage converted to a simple room typically costs £10,000 to £15,000, rising to £15,000 to £20,000 with plumbing for an office or shower room, and £20,000 to £25,000 or more for a double garage or a high specification. A detached garage converted and serviced runs £15,000 to £28,000. Indicative London ranges for 2026, quoted after a survey.
Do I need planning permission for a garage conversion?
Usually not for an integral garage, because the work is largely internal and generally falls within permitted development. Infilling the garage door changes the external appearance, which is where it can tip over. The right can be removed by an Article 4 direction or by a condition on the estate's original planning permission, and flats have no householder permitted development at all. Check the deeds too, since a covenant may require the parking space to be kept.
Does a garage conversion need building regulations approval?
Always. A garage was not built to habitable standards, so the conversion has to add a damp proof membrane and insulation to the floor, insulate the walls and roof, provide ventilation and extraction, meet fire separation requirements where it adjoins the house, and have the new electrical circuits certified under Part P by a registered electrician. Building control inspects at the stages that matter and issues a completion certificate.
How long does a garage conversion take?
Three to four weeks on site for a single garage converted to a simple room, four to five weeks where plumbing is involved, and five to seven weeks for a double garage or a higher specification. A detached garage takes longer, at five to eight weeks, because services usually have to be run to it. Add time beforehand for the building regulations application.
Will a garage conversion add value?
Usually, but it depends on what off-street parking is worth on your street. In outer boroughs with unrestricted parking it almost always adds more than it removes. In a controlled parking zone, or where off-street parking is priced into local asking figures, the arithmetic is closer. A useful test is whether you actually park a car in it, since most garages built before about 1980 are too narrow for a modern one.
Can you convert a garage into a bedroom?
Yes, provided it meets the requirements for a habitable room. That means insulation to current standards, a damp proofed and usually raised floor, adequate ventilation, and under Part B a compliant escape window or an alternative approved escape route. Fire separation from any remaining garage space or from an integral door into the house also has to be dealt with.
Adding Space
Other Ways to Add Space
If the garage is not the right answer, these are the routes that usually are.
Related pages
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