UB9 · Harefield & Denham
UB9 straddles the London boundary: Harefield and South Harefield sit in Hillingdon, while Denham and the Colne-side fringe lie outside it, in Buckinghamshire and Hertfordshire — so the deciding authority changes with the address, not the postcode. The Hillingdon side is village core and suburban housing, with Colne Valley farmland and water beyond. Green Belt covers much of this western edge, so scale and openness govern anything beyond a modest addition; the historic village core carries conservation designation; and the borough's Article 4 directions — HMO conversion, and extensions in defined areas — can remove the permitted-development fallback.
Location data: postcodes.io · Constraints: planning.data.gov.uk (borough-level) · Open Government Licence
Constraint context · Hillingdon
Real · planning.data.gov.ukHillingdon has 31 designated conservation areas and 4 Article 4 areas. A district is too coarse to say which apply to your house — postcode districts span many streets and UB9 crosses 3 boroughs. Enter a full postcode below for the point-level check, or read the full borough picture on the Hillingdon planning guide.
Is UB9 in a conservation area?
Partly — and which part matters. A postcode district is never uniformly designated: UB9 contains 1 conservation area within 1km of its centre, and whether your own property sits inside one decides whether permitted development survives. The centre point of UB9 itself does not fall inside one — but many of its streets will.
| Widewater Lock | Nearby |
Conservation areas whose official geometry lies within 1km of the centre of UB9. Source: planning.data.gov.uk · Open Government Licence. Proximity to the district centre is not a statement about your own address — run the address check for that.
Does an Article 4 direction apply in UB9?
Yes — UB9 has 1 Article 4 direction mapped within 1km of its centre. An Article 4 direction withdraws specific permitted-development rights on the streets it covers, which is the most common reason a project that looks like permitted development turns out to need a full application. The centre point of UB9 falls inside Residential extensions.
| Residential extensions | At the centre |
Article 4 directions whose official geometry lies within 1km of the centre of UB9. Source: planning.data.gov.uk · Open Government Licence. The national dataset omits some property-specific directions — the council register is always definitive.
Every designation in the borough: Hillingdon planning guide →
Do you need planning permission in UB9?
Three routes exist, and which one you are on is decided by your address, not your postcode district:
| Permitted development — no application. The work stays inside the GPDO limits and no designation removes them. A Lawful Development Certificate is cheap proof for a future buyer. | No permission |
| Prior approval — the larger single-storey rear extension route, with neighbour consultation. Not available on designated land. | 42 days |
| Full householder application — required once a designation removes your permitted-development right, or the scheme exceeds the limits. | 8 weeks |
UB9 contains mapped conservation-area or Article 4 geometry, so a meaningful share of its streets will have lost some permitted-development rights — which pushes those properties onto the full-application route. Whether yours is one of them is an address-level question, not a district-level one.
What does planning permission cost in UB9?
| Householder planning application | £548 (from 1 April 2026) |
| Lawful Development Certificate — proposed works | £274 (half the application fee) |
| Lawful Development Certificate — existing works | £548 (the full application fee) |
| Listed building consent | No fee |
| Resubmission after a refusal | Free once, within 12 months of the decision |
National statutory figures for England — councils do not set them, so they are the same in every borough. Planning fees re-index every 1 April; confirm the current amount on the Planning Portal fee calculator before you apply. These are the council's fees only — drawings, surveys and any specialist reports are separate.
How long does it take?
| Householder application — statutory target | 8 weeks |
| Householder application — in practice | 8–12 weeks |
| Prior approval (larger home extension) | 42 days |
| Lawful Development Certificate | 8 weeks |
| Householder appeal — deadline to lodge | 12 weeks from the decision date |
| Householder appeal — typical decision | Around 18 weeks |
What if it's refused?
A refusal is a decision notice with reasons attached, and those reasons are a roadmap. Most homeowners in Hillingdon — as anywhere in England — are better served by amending the scheme and using the free resubmission than by appealing: you get one further application on the same site within 12 months without paying again.
| Who can appeal | The applicant only — not neighbours |
| Fee to appeal | None — you bear your own costs |
| Procedure | Written representations for most householder appeals |
| Success rate | Roughly a third — about 36% of householder appeals allowed in 2025/26 |
Appeals go to the Planning Inspectorate, an independent national body. How to read a refusal and choose your route →
Planning permission by project in Hillingdon
Ruislip, Eastcote and Uxbridge stock extends under PD; the village conservation areas, Green Belt and the borough's extension Article 4 can need a full application.
Rear extension in Hillingdon →Workable on the Uxbridge and Hayes terraces; the village conservation areas and the borough's Article 4 directions can need a full application.
Side return extension in Hillingdon →Strong on the Ruislip and Eastcote semis under PD; the village conservation areas scrutinise dormer design.
Loft conversion in Hillingdon →Uncommon on the borough's suburban plots; a full application with structural and ground-condition evidence is expected, with Green Belt limits in the west.
Basement extension in Hillingdon →Large suburban and Green Belt-edge gardens suit garden rooms under PD; conservation areas and the borough's Article 4 directions are where outbuilding rights tighten.
Garden room in Hillingdon →Pinpoint your street
More of Hillingdon
Ruislip and Harefield villages to Heathrow and the Colne Valley; HMO and extension Article 4s.
Borough page →Planning Permission Checker provides planning and cost intelligence for early feasibility only. It is not legal, planning, valuation, architectural, structural, or surveying advice. All estimates are indicative and must be verified by qualified professionals before purchase, design, planning submission, or construction.
Cost estimates are indicative only — not a quotation. Final price depends on survey, specification, structure, access, party wall matters, VAT, professional fees, and contractor availability.
Planning outcomes are not guaranteed. Local planning authorities make final decisions.