Garage conversion costs in 2026: real prices, three worked examples
National guides quote £7,000 to £32,000, which tells you nothing. These are 2026 prices for the Aylesbury area, broken down the way we quote them — with three complete worked examples you can hold your own quotes against.
How much does a garage conversion cost in 2026?
Around Aylesbury in 2026: a single garage converts for £12,000–£20,000 (dry room at the lower end, plumbing at the upper), a double for £18,000–£28,000+, and an annexe with en-suite for £26,000–£34,000. Per square metre that's roughly £850–£1,250/m² — under half the rate of building an extension.
Every figure on this page assumes the job is done properly: building regulations sign-off, insulation to current values, certified electrics, and the completion certificate at the end. Quotes meaningfully below these ranges are usually missing one of those things — most often the certificate, which is the expensive thing to be missing. What the money physically buys is described wall-by-wall on the single garage page.
What does each type of room cost?
The use drives the price more than the garage does. A dry room (office, snug, playroom) is the baseline; plumbing adds £3,000–£5,500; sleeping accommodation adds escape-window and fire-safety spec; an annexe stacks most of the above. The table below shows 2026 ranges per use for a typical single garage.
| Use | Typical 2026 range | What pushes it up |
|---|---|---|
| Snug / playroom / dining room | £12,000 – £16,500 | Glazing spec, flooring choice |
| Home office | £13,500 – £18,500 | Acoustic linings, data, heating choice |
| Gym | £12,500 – £16,000 | Floor loading, ventilation capacity |
| Utility room / WC | £15,500 – £20,000 | Drain run length, extract ventilation |
| Guest bedroom | £15,500 – £20,000 | Escape window, acoustic spec |
| Bedroom with en-suite | £18,500 – £26,000 | Drainage answer — gravity vs pumped |
| Annexe (double garage) | £26,000 – £34,000 | Wet room, kitchenette, accessibility spec |
What does an integral single on Kingsbrook cost?
£14,750 — a 2026 home office conversion, start to certificate. A typical Kingsbrook integral garage (5.1m × 2.7m), dry slab, consumer unit with capacity, converted to an office. Includes the covenant consent the estate commonly requires — the line item most quotes forget.
| Item | Cost |
|---|---|
| Developer/management covenant consent (admin fee + drawings pack) | £350 |
| Infill wall, foundation, escape-spec window | £3,200 |
| Floor build-up: DPM, insulation, screed, flooring | £2,500 |
| Wall/ceiling linings with acoustic wool, skim | £3,300 |
| Electrics (new circuit, desk-height sockets, lighting) + 2× CAT6 | £1,900 |
| Electric underfloor heating + smart stat | £1,150 |
| Solid-core door, decoration | £1,200 |
| Drawings, building control, completion certificate | £1,150 |
| Fixed total | £14,750 |
On site: 2.5 weeks. Note what the integral layout saves: no roof work, three walls already house walls, short service runs. That's why integral conversions anchor the bottom of the cost range.
What does a detached single in Wendover cost?
£21,400 — a garden-room/office conversion of a detached brick garage. Detached is the expensive way to convert a single: the roof needs insulating and re-felting, power has to cross the garden in an armoured cable, and there's no house wall to borrow warmth from. Worth it when the building and the need line up — priced honestly here.
| Item | Cost |
|---|---|
| Infill wall, foundation, window + glazed door | £3,900 |
| Flat roof: re-cover + insulate to 0.18 W/m²K | £3,600 |
| Floor build-up: DPM, insulation, screed, flooring | £2,600 |
| Wall linings all four walls (no shared house walls), skim | £3,700 |
| Trenched armoured supply from house, new small consumer unit | £1,900 |
| Electrics, lighting, data over the same trench | £1,700 |
| Air-to-air heat pump (heating + summer cooling) | £2,100 |
| Drawings, building control, completion certificate | £1,200 |
| Decoration | £700 |
| Fixed total | £21,400 |
On site: 4 weeks. Compare before committing: a garden-office pod of similar internal size runs £15,000–£25,000 and isn't masonry, isn't on foundations, and doesn't appraise as permanent floor area. The conversion usually wins if the garage already stands; it rarely justifies building a garage to convert.
What does a double in Princes Risborough cost?
£24,900 — a full conversion of an attached double into two rooms. A 1980s attached double (5.4m × 5.2m) with one wide door, converted to a family room plus utility with WC. The wide opening needs an engineer-checked beam; the utility sits at the house end where the drains are.
| Item | Cost |
|---|---|
| Engineer's calculations + beam verification over wide opening | £650 |
| Infill wall with two windows, matched brick | £4,400 |
| Floor build-up across 28m² | £3,900 |
| Pitched roof insulation + wall linings, skim throughout | £4,600 |
| Internal partition with acoustic insulation, 2 doors | £1,700 |
| Utility/WC: drainage connection (gravity, 4m run), plumbing, extract, sanitaryware | £3,800 |
| Electrics: two circuits, lighting, sockets | £2,300 |
| Radiators teed from house circuit (boiler checked, had capacity) | £1,050 |
| Drawings, building control, completion certificate | £1,300 |
| Flooring & decoration | £1,200 |
| Fixed total | £24,900 |
On site: 4.5 weeks. Per square metre this lands near £890/m² — doubles convert cheaper per metre than singles because the fixed costs (drawings, building control, scaffold, setup) spread across twice the floor. Full options for doubles, including the half-conversion route, are on the double garage page.
What should a garage conversion quote include?
Everything on this checklist — or the price isn't a price. Drawings; building control fees and the completion certificate; structural calculations where openings are involved; damp-proof membrane and floor build-up; insulation to stated U-values; certified electrics; making good externally; and VAT. "From" prices usually omit two or more of these.
- The certificate question: ask "is building control sign-off included, and who submits the application?" A pause is your answer. This is the single best quote-filter there is — the value guide explains what the missing certificate costs at sale time.
- The provisional-sums question: ask what happens if the slab is worse than expected. A fixed quote prices the risk; an estimate passes it to you in week two.
- The covenant question: on a newer estate, ask who's checking the deeds. If the answer is "that's your side", budget the consent process yourself — or find a builder who checks it for you.
Cost questions
Why do 2026 prices vary so much between builders?
Mostly scope, not margin: the cheap quote usually excludes drawings, building control, structural checks or making good — the £3,000–£4,000 of invisible work that makes the room legal. Compare quotes line by line against the checklist above, not total against total.
Is VAT included in these figures?
Yes — every figure on this page and in our quotes includes VAT. A surprising number of "from" prices you'll see elsewhere don't, which flatters them by 20% until the invoice arrives.
What's the cheapest legitimate way to convert?
An integral garage to a dry room, keeping the internal door where it is, radiator teed from the house circuit, standard window, simple flooring — realistically £12,000–£13,500 in 2026 with nothing important skipped. Cheaper than that means something's missing.
How do conversion costs compare with an extension?
Conversions run £850–£1,250/m²; single-storey extensions in this area run £2,400–£3,200/m² before kitchens and glazing. The full comparison — cost, disruption, permission, time — is in conversion vs extension.
Will your quote match these examples?
The examples are real shapes of real jobs, but your slab, drains, consumer unit and deeds are yours — that's why the survey exists. What we promise: the quote you get is itemised like the tables above, fixed once surveyed, and includes the certificate. Book the survey and see.