Single & integral garage conversions
A single garage gives you about 14m² — the size of a double bedroom. It is already built and already under your roof. This page shows what we do to it, surface by surface, and what it costs.
Integral, attached — and why it matters
An integral garage sits inside the footprint of the house, under the same roof, usually with a connecting door from the hall. This is the standard arrangement on Aylesbury's newer estates, and it's the simplest conversion there is. Three of the four walls are already house walls. The ceiling usually has a heated room above it. Your heating and electrics are within a few metres. The work concentrates on one wall, one floor, and the services.
An attached garage shares one wall with the house and has its own roof. The conversion adds two jobs: the roof needs insulating (and occasionally re-felting while we're up there), and connecting the room to the house properly usually means forming a new doorway through the shared wall — a structural opening with a lintel, and the one point where the Party Wall Act can come into play if that wall is shared with a neighbour rather than your own house.
Everything on this page applies to both; where the attached case costs more, the cost table says so. Detached garages are a different conversation — services have to cross the garden and the planning position changes (see the permitted development guide) — and we quote those individually after a survey.
What's actually involved — in plain English
Most quotes hide the work behind the word "conversion". This is what physically happens to each part of the garage, and the standard each element has to reach before building control will sign it off.
The door opening
The up-and-over door comes out, and the opening gets a proper foundation trench and a new insulated cavity wall — not a sheet of studwork behind a fake door. We tooth the outer brick or blockwork into your existing wall and match the brick, the mortar colour and the joint style, so from the street it reads as a wall with a window in it, not a filled-in garage. Because this is a brand-new piece of external wall, building regs hold it to the strictest insulation standard on the whole job: a U-value of 0.18 W/m²K or better.
The floor
Garage slabs are usually 50–150mm lower than the house floor, laid to a slight fall towards the door, and cast without a damp-proof membrane — none of which matters for parking a car and all of which matters for a bedroom. We lay a heavy-gauge membrane across the slab, lapped into the existing damp-proof course in the walls, then rigid insulation, then a screed or chipboard deck that lands the finished floor level with the house — a step-free threshold, with the slope swallowed inside the build-up. Target U-value: 0.25 W/m²K.
The walls
A garage's external walls are often a single skin of brick — fine for a car, hopeless for a living room. Each external wall gets an insulated lining: treated battens or metal frame, insulation between and over, a vapour control layer, then plasterboard and skim. Done properly this costs you only about 60–90mm per wall. Upgraded walls need to hit 0.30 W/m²K; where a wall shows any history of damp we tank it first, because insulation over damp brick just hides a problem you'll meet again.
The ceiling
In an integral garage with a bedroom above, the ceiling is already inside the insulated envelope and mainly needs fire-rated boarding and acoustic quilt. Where the garage has its own roof, we insulate at ceiling level or between rafters to 0.16 W/m²K — the tightest target after the infill wall, because heat leaves upwards first.
Heating
Usually one of two routes: a radiator teed off the house circuit (cheapest where pipe runs are short, which in an integral garage they almost always are), or electric underfloor heating laid in the new floor build-up — no wet pipework, gentle even warmth, and it doesn't depend on your boiler having spare capacity. We check the boiler at the survey and recommend accordingly rather than defaulting to whichever is easier for us.
Electrics
The single garage socket and strip light don't survive the conversion. A new circuit (or circuits) runs from your consumer unit: typically six to eight double sockets, LED lighting, and any specials — a spur for an electric radiator, wired data for an office. All notifiable work under Part P, all certificated, with the certificates handed to you at the end. If your consumer unit is an older type without spare ways, the survey flags it and the quote prices it — that's a common "surprise" on other people's jobs and it shouldn't be.
The window
The new window sits in the infill wall where the door was — the room's main daylight, so we size it generously and align its head height with your existing windows so the elevation looks original. Double-glazed as standard, trickle vents for background airflow, and if the room could ever be used as a bedroom we spec it as an escape window from day one: clear opening of at least 0.33m², minimum 450mm each way, cill no higher than 1100mm — it costs nothing extra to get right at order time and future-proofs the room.
Every element above, with the full requirement list and what building control measures, is in the building regulations guide.
What it costs: £12,000 – £20,000
Nearly every single garage conversion we price lands inside this band. Your quote is fixed once we've surveyed — here's the anatomy of the number, and what moves it up or down.
| Element | Typical share | Notes |
|---|---|---|
| Infill wall, foundation & new window | £2,500 – £4,000 | Matched brickwork; the window spec moves this most |
| Floor: membrane, insulation, screed/deck | £1,800 – £3,000 | Deeper slabs need more build-up |
| Wall & ceiling linings, insulation, plaster | £2,800 – £4,200 | Attached garages add roof insulation here |
| Heating & electrics | £1,800 – £3,200 | Radiator tee vs electric UFH; consumer unit condition |
| Drawings & building control | £700 – £1,400 | We prepare, submit and attend all inspections |
| Second fix & decoration | £1,400 – £2,600 | Flooring, skirting, internal door, paint |
| Typical total — dry room | £12,000 – £17,500 | Snug, office, playroom, dining room |
| With plumbing (utility / WC) | £15,500 – £20,000 | Adds drainage, water, extract ventilation |
What moves the number
- Up: plumbing of any kind; a consumer unit that needs upgrading; a slab with damp or level problems; attached garages needing roof work or a structural opening; premium windows or bi-fold-style glazing in the infill.
- Down: an integral garage with sound slab and dry walls; keeping the existing internal door position; a simple radiator tee; standard white uPVC window; you handling the final decoration yourself.
What never moves it: extras invented mid-job. If the survey can't fully de-risk something — say, slab condition under existing flooring — the quote says so explicitly and prices the worst case, so surprises can only be in your favour.
Timeline: what happens when
- Before we start (1–2 weeks)
Survey, covenant and permitted development checks, fixed quote, drawings, building control submission and materials ordering — all off-site, no disruption.
- Week 1 — structure
Door out, foundation and infill wall built, window in, floor membrane and insulation down. The room is weathertight by the end of the week.
- Week 2 — services & linings
First-fix electrics and heating, wall and ceiling linings, insulation, plasterboard and skim. Building control's insulation inspection happens here.
- Week 3 — finish
Screed cured, flooring, second-fix electrics, radiator on, skirting, doors, decoration. Final building control visit and sign-off.
That's the typical 2–3 week pattern for a dry room in an integral garage. Plumbing adds around a week; attached garages with roof work add a few days. You get the programme in writing with the quote, and because the approval and ordering happen before day one, on-site overruns are rare.
Building regs sign-off is part of the job
Every conversion we do runs through building control — either Buckinghamshire Council's team or an approved inspector — with the application made by us, inspections attended by us, and the completion certificate delivered to you at handover alongside the electrical certificates.
This isn't bureaucratic box-ticking. The certificate is what makes your conversion an asset instead of a liability: without it the room legally isn't habitable space, your buyer's solicitor will flag it, their surveyor will discount it, and you'll end up paying for a regularisation application on someone else's timetable. With it, the room counts — in the floor area, in the bedroom count if it qualifies, and in the valuation.
What building control actually inspects
Foundations for the infill wall before they're poured · the floor membrane and insulation before screed · wall and ceiling insulation before boarding · and a final visit checking ventilation, fire safety and the finished room. We schedule all of it; you don't chase anyone.
And on the planning side: whether your conversion needs any application at all is covered in the permitted development guide.
Single garage questions
How much does a single garage conversion cost?
Between £12,000 and £17,500 for a dry room around Aylesbury, or £15,500 – £20,000 with plumbing. The cost table above shows where every pound goes — and your written quote is fixed, not indicative.
Do I need planning permission for a single garage conversion?
Usually not — internal conversion works fall under permitted development for most houses. The exceptions we check for at every survey: conservation areas, listed buildings, flats, estates where permitted development rights were removed by planning condition, and deed covenants requiring the garage to stay a garage. Around nine in ten of our jobs need no application at all.
Will it be as warm as the rest of the house?
It should end up warmer than most of it. The insulation targets for converted elements — 0.30 walls, 0.25 floor, 0.16 ceiling, 0.18 for the new infill wall — are modern-house standards, stricter than what most 1990s-and-earlier houses achieve anywhere else. Cold converted garages are unregulated conversions; that's precisely what the sign-off prevents.
Will it look like a converted garage from outside?
Not if the infill is done as a real cavity wall with toothed-in, colour-matched brickwork and a window aligned to the house's existing openings — which is how we build them. The conversions you can spot from the street are the ones built as studwork behind a retained door, or bricked up without matching.
Where does everything in the garage go?
Honestly: for most people, into the loft, a slimline shed and two trips to the tip — the car hasn't fitted in years. If you have genuine bulk storage needs, look at a half-conversion on our double garage page, or we can build generous storage into the new room's design.
Get a fixed price for your garage
Free survey with covenant and permitted development checks included. Fixed written quote — typically built in 2–3 weeks.