A Hillingdon garage that currently stores bicycles can become a bedroom, a study or the far end of an open-plan kitchen. We settle the planning route first, then draw the full building regulations package: Part L thermal upgrade, fire and escape provision, and structural calculations for every wall that goes.
Usually, on an attached garage with no new opening onto a highway. Hillingdon’s Datahub set records 1,124 garage conversion applications at 78% approved, and the borough issued 1,756 lawful development certificates. Its 150 Article 4 areas are the check that most often changes the answer.
| Measure | Hillingdon | Outcome |
|---|---|---|
| Garage conversion applications in the Datahub | 1,124 | 78% approved |
| Lawful development certificates issued | 1,756 | — |
| Article 4 areas in the register | 150 | fifth most of the 16 boroughs in the Article 4 register |
| Householder decisions | 3,978 | 84.2% approved |
| Certificate application fee | £274 | statutory, England 2026 |
| Building regulations package | from £840 | our fixed fee |
Sources: row one from the Planning London Datahub, retrieved 15 August 2026 — phrase-matched descriptions, comparable within Hillingdon only. Rows two and four from MHCLG PS1 and PS2, twelve quarters to March 2026. Row three from the MHCLG Planning Data Platform register, retrieved 1 September 2026. Row five from the Fees for Applications Regulations 2012 as amended; row six is our own published fixed fee.
For Hillingdon homeowners in 1930s semi-detached dominates; Metropolitan Green Belt covers much of north Hillingdon; Victorian cottages in Uxbridge and Ruislip villages; post-war housing near Heathrow, a garage conversion drawings package is the full measured-survey-to-submission drawing set London Borough of Hillingdon needs in order to determine an application: existing and proposed plans, elevations and sections at 1:100 and 1:50, a location and site plan, and the supporting statements the case officer asks for.
Prepared and reviewed by the chartered technologist team at Architectural Drawings London — MCIAT chartered, £2m PI insured.Last reviewed 2026-08-03.
Turn your unused Hillingdon garage into a bedroom, home office or open-plan kitchen-diner. Planning route assessment, full building regulations drawings with Part L thermal compliance, structural calculations for any removed walls.
Housing stock in Hillingdon: 1930s semi-detached dominates; Metropolitan Green Belt covers much of north Hillingdon; Victorian cottages in Uxbridge and Ruislip villages; post-war housing near Heathrow.
Character: Largest outer west London borough; significant Green Belt; Heathrow noise contours affect planning decisions in Harmondsworth and Sipson.
Most integral garage conversions are internal work and need no planning permission at all. A detached garage, a Green Belt plot or a changed frontage can each turn that answer around, so yours is checked before we quote.
A laser-measured record of the garage itself and of the rooms it will open into, because those are the walls the calculations have to account for.
Floor plans, elevations and sections at 1:50 for the garage as it stands and as it will be, specified to the level Building Control signs off rather than the level a builder can price.
A garage floor, walls and roof were never built to hold heat. Meeting Part L means insulation throughout, glazing at compliant U-values, and a heating specification that actually covers the new room.
Where the garage door comes out and a wall with a window goes in, that opening needs a designed steel beam on padstones — as does any load-bearing wall taken down between the garage and the house.
The Full Plans submission goes to Hillingdon Council Building Control or to an approved inspector, whichever you prefer, and we run the inspection stages through to the completion certificate.
Single planning or regs submission.
Planning + building regs + structural.
Listed, conservation, complex sites.
Move the controls for an indicative figure. It anchors your budget — it is not a quote. Every project is priced after a free survey.
Build costs are separate and quoted by your contractor. See our published fees.
The Hillingdon postcode districts we work in, the housing that dominates each one, and the authority that validates the drawings. The fee column carries 2026 statutory application charges set by government, which have nothing to do with what a conversion costs to design.
| Postcode | Area | Dominant stock | What it means for a garage conversion |
|---|---|---|---|
| UB3 | Hayes / Harlington | 1930s semi-detached, post-war estates | Hayes and Harlington sit entirely within UB3, so every conversion drawn from a UB3 address is validated by Hillingdon Council and nobody else. |
| UB4 | Hayes / Yeading | 1930s semi-detached, post-war estates | UB4, covering Hayes and Yeading, is undivided in the same way: the borough is the only authority a UB4 application can reach. |
| UB7 | West Drayton / Sipson / Harmondsworth | 1930s semi-detached, post-war | A garage conversion at an UB7 address in West Drayton / Sipson / Harmondsworth is determined by Hillingdon Council under its own Local Plan policies for West Drayton / Sipson / Harmondsworth. |
| UB8 | Uxbridge / Cowley | Georgian fragments, 1930s semi-detached, post-war flats | UB8 is Uxbridge and Cowley alone, wholly inside the borough, so Hillingdon validates the conversion and its officers work to the UB8 conservation area mapping. |
| UB9 | Denham / Harefield | Tudor and Georgian fragments, 1930s semi-detached | UB9 reaches across the northern edge of the borough at Harefield and out towards Denham. Hillingdon determines the Harefield side; Green Belt designation is the first thing to check here before anything detached is converted. |
| UB10 | Hillingdon / Ickenham | 1930s semi-detached, Tudor fragments | UB10 takes in Hillingdon village and Ickenham, both inside the borough, so one authority and one Local Plan apply right across the district. |
| UB11 | Stockley Park | Interwar semis dominate: the VOA's March 2025 count places 29.8% of Hillingdon's 118,250 dwellings in the 1930 to 1939 band. Green Belt runs across the northern half of the borough, older cottages survive in the Uxbridge and Ruislip villages, and post-war housing fills the ground towards Heathrow. | A garage conversion at an UB11 address in Stockley Park is determined by Hillingdon Council under its own Local Plan policies for Stockley Park. |
| HA4 | Ruislip | 1930s semi-detached, Tudor cottages | A Ruislip address in HA4 is decided by Hillingdon under its own Local Plan, where the older village core carries noticeably tighter expectations than the interwar streets around it. |
Hillingdon spreads over 11,570 hectares, of which 57.2% carries buildings (OS Open Built Up Areas, retrieved 2 September 2026). Plot depth, wall build-up and roof pitch change markedly between Ruislip, Uxbridge and Hayes, and each of those changes what a conversion can achieve at a particular address.
Conservation areas covering Hillingdon: Hillingdon Council runs 29, and Northwood, Harefield, Ickenham are the ones Hillingdon owners meet most. A garage conversion inside a Hillingdon conservation area loses permitted development, so the Hillingdon submission is a householder application at £548 decided in 8 weeks — not a £249 prior approval decided in 6 weeks. In Northwood a garage conversion is judged on the street elevation first.
Hillingdon permitted development status: there is no borough-wide direction from Hillingdon Council, so a garage conversion at a HA4 address is normally still permitted development. We certify that with a £274 Lawful Development Certificate rather than leaving a Hillingdon sale to argue it later.
Hillingdon housing stock: 1930s semi-detached dominates; Metropolitan Green Belt covers much of north Hillingdon; Victorian cottages in Uxbridge and Ruislip villages; post-war housing near Heathrow. Largest outer west London borough; significant Green Belt; Heathrow noise contours affect planning decisions in Harmondsworth and Sipson. Read that before choosing a garage conversion route in Hillingdon — construction, not postcode, sets what is achievable. Hillingdon Council charges £548 for a householder application and has 8 weeks to determine it.
Sources for this Hillingdon garage conversion page: borough policies maps and conservation-area registers (2025–26), Royal Mail postcode district boundaries, the Town and Country Planning (Fees for Applications) (England) Regulations, the Town and Country Planning (General Permitted Development) (England) Order 2015 as amended, and the Party Wall etc. Act 1996.
Converting a garage or an outbuilding into living space is normally decided as a change of use, and 97 such Hillingdon decisions were taken as far as an inspector in the decade of Planning Inspectorate records ending 2026. 44 were allowed, 53 dismissed: 45.4% succeeded, against 29.1% for the same casework type across London. Read that carefully. Only refused applicants who decided to fight ever appear in it, so it is not a permission rate. What it does say is that a Hillingdon refusal is overturned more often than the city-wide pattern would suggest, and that is an argument for exhausting the design conversation with the case officer before the decision rather than after it.
Half of those appeals took longer than 108 days to decide, counted from the day the appeal started and added on top of the council's own determination time — the practical argument for getting the application right at the first attempt. 7.2% touched the setting of a listed building. 92.8% were settled on written representations alone, with no hearing and no inquiry, so an inspector saw nothing beyond the drawings and the written statement.
Drawn from the 97 change-of-use appeals decided for Hillingdon in the Planning Inspectorate casework record, published under OGL v3.0.
The questions Hillingdon owners put to us before starting a garage conversion. One number is worth having in front of you first: the borough received 6,013 applications over twelve quarters of MHCLG reporting ending last March, and 316 were withdrawn before any decision was issued. That is 5.3%, where the 33 boroughs pooled withdraw 6.9% (PS1, Open Government Licence v3.0). Schemes here are seen through rather than quietly pulled, which makes the refusal record, not the withdrawal rate, the thing to plan against.
Start a free quote →Most integral garage conversions in Hillingdon do not require planning permission — they're classed as an internal alteration, which is not development under the TCPA 1990. However, if the conversion materially alters the external appearance (new windows, raising the roof), planning permission may be required. Detached garage conversions to habitable use always need planning. Article 4 Directions in Hillingdon may also affect eligibility. We confirm the planning route before quoting.
Of the ways to add a habitable room, converting the garage is usually the cheapest, because the walls, roof and foundations are already standing. Our package covers the planning route assessment, the building regulations drawings and the structural calculations for the door opening. What moves the build cost is whether the garage is integral or detached, and how much insulation, floor build-up and new services it needs — more than floor area does. Current figures are on our fees page.
Yes, without exception. Turning a garage into habitable space is a material change of use under the Building Regulations. In practice that means insulation to Part L, escape and fire separation under Part B, a damp solution under Part C for a slab never designed to be lived on, ventilation under Part F, and structural design wherever the door opening is filled in.
Usually, though not for the reason most sites give. We will not put a percentage on the value added, because no one publishes one that holds across a borough. Here is what is published: the median Hillingdon home sold for £510,000 during 2025 across 2,458 recorded transactions, 4.1% above the 2024 median of £490,000 (HM Land Registry Price Paid, retrieved 2 September 2026). Set against a figure like that, turning dead storage into a fourth bedroom costs a fraction per square metre of what an extension costs, since the shell exists already. Where parking is tight, or the garage is genuinely in use, the arithmetic can run the other way.
Building an integral conversion takes roughly 4 to 6 weeks once the drawings are approved. Our own stage — survey, drawings, calculations, Building Control submission — runs 3 to 4 weeks. Allow three to four months end to end, from the first site visit to a completion certificate.
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