The garage you barely use is most of a room already. The four walls and the roof are there, so a garage conversion gives you a bedroom, home office, playroom or annexe for a fraction of what a brick extension costs — without losing an inch of garden. We design and build to a fixed price, and in North London the conversion is built by Pine Grove's own team to the standard that keeps it warm, dry and signed off. This page covers what your garage can become, what it costs by type, the planning reality (honestly), and why the building regulations are the part you don't skip.
What is a garage conversion?
A garage conversion turns an existing garage — attached, integral, double or detached — into a fully habitable room within the footprint you already have. Because the shell exists, you're not paying for foundations, external walls or a roof. You're paying to make a cold, single-skin, damp-prone store into a room that meets building regulations: insulated, ventilated, weather-tight and warm.
Three numbers explain why it's so popular in London:
- A typical single garage gives you 12–18 m² of new internal space.
- The work takes 3–6 weeks start to finish — far quicker than a rear extension.
- It's usually the most affordable way to add a room to a house, because the structure is already built.
Most London garages — on 1930s semis, post-war estates and newer developments across Enfield, Barnet, Southgate and Cockfosters — sit unused or hold a freezer and some bikes. Converted, they become the spare bedroom, the office that ends the kitchen-table commute, or the annexe for a relative.
What can a garage become?
Almost any habitable room. The most-searched conversion in the UK is "convert garage to bedroom". Here's what London homeowners turn their garages into:
| End use | What's involved | Typical demand |
|---|---|---|
| Bedroom | Insulation, heating, window; carpet/flooring | The spare room or a teenager's room |
| Bedroom with en-suite | As above plus plumbing, drainage, a small shower room | Adds the most value; pushes cost up |
| Home office | Power, data, good insulation and natural light | Surged since home working |
| Living room / snug | Open it to the hall, plaster, heat, decorate | Great for growing families |
| Playroom | Warm floor, durable finish, safety | Keeps the mess in one room |
| Utility room | Plumbing for washer/dryer, worktop, storage | Frees up the kitchen |
| Self-contained annexe | Kitchenette, shower room, own entrance | For relatives or rental — most complex |
The simplest conversions (office, bedroom, playroom) are the cheapest because they need no plumbing. The moment you add a tap — an en-suite, a utility, an annexe — you're into drainage and you move up the price range. We design around what you actually need so you're not paying for plumbing you won't use.
How much does a garage conversion cost in London?
Cost depends almost entirely on the type of garage you're starting with, because each one starts from a different point. An integral garage already has three or four heated walls around it; a detached garage out on its own usually needs new heating runs and often drainage, so it costs the most.
| Garage type | What it starts with | Cost (2026) |
|---|---|---|
| Integral garage | Built into the house — walls already partly heated | £10,000 – £14,000 |
| Single (attached) garage | One external wall, shared house wall | £12,000 – £24,000 |
| Double garage | Twice the floor area, bigger spans | £15,000 – £30,000 |
| Detached garage | Standalone — needs new heating, often drainage | £18,000 – £35,000 |
As a per-square-metre guide, a standard-spec conversion runs around £1,440–£1,920 per m². Three things move you toward the top of any range: adding plumbing (en-suite, utility or kitchenette), a premium finish, and a detached structure that needs services brought to it. All work from a VAT-registered builder carries 20% VAT — always check whether a quote includes it. Our garage conversion cost guide breaks every type down line by line.
Do you need planning permission? (The honest answer)
Most garage conversions are permitted development — you're converting within the existing structure, not enlarging it, so a full planning application usually isn't needed. But "usually" is doing real work in that sentence, and cheap converters who tell you "you never need permission" are wrong. Here's where it isn't permitted development:
- Permitted development rights have been removed. Many newer estates, and homes under an Article 4 direction, have had PD rights stripped — so removing the garage door and changing the use needs permission.
- Listed buildings and conservation areas — common in pockets of Highgate, Winchmore Hill and Monken Hadley — carry extra controls.
- A parking condition exists. This is the big one in London. The original planning permission on many newer developments requires the parking space to be retained. Convert the garage and you've breached the condition. Always check the original permission.
Where none of these apply, you're free to proceed. But you should still get a Lawful Development Certificate (£274) — it's the official document proving your conversion was lawful, and it makes selling the house far smoother. If permission is needed, it's a £548 householder application (April 2026 fee) plus the £91.02 planning portal charge. We check the planning position for your specific address before any work starts — no nasty surprises.
Why building regulations matter (the bit cheap converters skip)
Here's the part that catches people out: planning permission is often optional, but building regulations always apply. Every habitable garage conversion has to meet them, and this is exactly where a cheap quote and a proper conversion part ways.
A garage is built to a lower standard than a house. The floor is usually a bare slab with no insulation and no damp proofing. The walls are often single-skin. There's no controlled ventilation. To make it a room you can legally and comfortably live in, the work has to include:
- Floor insulation and damp proofing — often raising the floor level. This is the single biggest hidden cost versus what people expect, and the most common corner cut.
- Wall insulation — bringing the external walls up to thermal standard.
- Moisture and ventilation control — so the room doesn't end up cold and damp.
Budget roughly £500–£1,200 for the building control side. A conversion that skips the floor and damp upgrade will look finished and then go cold, damp and mouldy within a winter or two — and it won't pass building control or survive a house sale. Every conversion we price includes the full building-regs work and sign-off, because a warm dry room is the entire point.
How it works — four steps
- Free site visit. We come to you anywhere in London, look at the garage, talk through what you want it to become, and check the planning and building-regs position for your address.
- Fixed-price design. You get a clear, itemised, fixed quote and a design — no day-rate creep, no "we found a problem" mid-build surprises.
- Build. The conversion — floor, damp, insulation, walls, glazing, services and finish — typically takes 3–6 weeks.
- Sign-off. Building control signs the work off, and where you've opted for it we sort your Lawful Development Certificate so it's all documented.
Garage conversion guides
Each of these goes deeper on one question:
- The rules: do you need planning permission for a garage conversion?, with parking conditions and Article 4 directions explained · lawful development certificates and when one is worth having
- The room itself: converting a garage into a bedroom, step by step · parking, partial conversions and the other practicalities · granny annexe rules, if the garage is becoming a self-contained annexe
Areas we cover
Pine Grove's own team converts garages across North London, including Enfield, Barnet, Southgate, Winchmore Hill, Palmers Green, Oakwood, Hadley Wood, Highgate and Muswell Hill. The North London house extensions page lists every town we cover there, borough by borough. Potters Bar and the Hertfordshire border are on our map too, and we also cover South London: every area we serve is on our locations page.
Thinking about converting your garage in London? Use our Extension Builder to price your conversion in seconds, or book a free site visit for a fixed, itemised quote. Call 020 3051 9430 — The Extension Company, North London and across London.