Side return extension in Hillingdon
Do you need planning permission for a side return extension in Hillingdon?
Workable on the Uxbridge and Hayes terraces where they survive; village conservation areas, Green Belt and extension Article 4 parcels can all force a full application. Side extensions have no permitted-development route inside a conservation area.
Workable on the Uxbridge and Hayes terraces; the village conservation areas and the borough's Article 4 directions can need a full application.
True side-return stock is a smaller slice of Hillingdon than continuous inner-London belts. On the dominant suburban semis, wrap-arounds with side access are often more natural. Officers still focus on boundary wall height, neighbour daylight and materials where a full application is needed.
What actually applies in Hillingdon
Conservation areas in Hillingdon
Real · planning.data.gov.ukEvery designated conservation area in Hillingdon from the official dataset — inside one, permitted development narrows and design scrutiny rises.
- Black Jacks Lock
- Botwell: Nestles
- Botwell: Thorn EMI
- Bulls Bridge
- Copper Mill Lock
- Coppermill Lock
- Cowley Church (St. Laurence)
- Cowley Lock
- Denham Lock
- Eastcote (Morford Way)
- Eastcote Park Estate
- Eastcote Village
- Harefield Village
- Harlington Village
- Harmondsworth Village
- Hayes Village
- Hillingdon Village
- Ickenham Village
- Longford Village
- Northwood Town Centre, Green Lane
- Northwood, Frithwood
- Old Uxbridge / Windsor Street
- Rockingham Bridge, Uxbridge
- Ruislip Village
- Ruislip, Manor Way
- Springwell Lock
- The Glen, Northwood
- The Greenway
- Uxbridge Moor
- West Drayton Green
- Widewater Lock
Source: planning.data.gov.uk · Open Government Licence. Boundaries are checked at address level by the area report.
Article 4 directions in Hillingdon
Real · planning.data.gov.ukHillingdon's Article 4 directions are recorded in the national dataset and are unusually wide-ranging: a borough-wide HMO direction (planning permission to convert a house to a small HMO), a direction removing permitted development for residential extensions in defined areas, and directions controlling commercial-to-residential conversion and the demolition-and-rebuild of commercial buildings. Green Belt covers much of the borough's west. Use the area report, or the council's Article 4 register, for the direction that applies at a given address.
Source: planning.data.gov.uk · Open Government Licence · 4 directions recorded. Checked at address level by the area report.
Prices: HM Land Registry UK House Price Index, December 2025 · Open Government Licence.
The planning route — PD or permission?
Under permitted development, side extensions (GPDO Class A) must be single storey, no more than 4m high and no wider than half the original house — but side extensions are excluded from PD entirely in conservation areas. Wrap-around schemes combining side and rear elements usually exceed PD limits and need full permission everywhere.
In practice, most London side returns proceed by full householder application. The good news is the precedent base: on streets of identical terraces, a consented side return three doors down is the strongest evidence your scheme can cite. Officers focus on the boundary wall height, neighbour daylight and the junction with the host roof.
Permitted development limits — side return extension
| Storeys | Single storey only |
| Maximum height | 4m |
| Maximum width | No wider than half the original house |
| Conservation areas | Side extensions excluded from PD entirely |
| Wrap-around (side + rear combined) | Usually exceeds PD — full permission |
Limits summarise the General Permitted Development Order (Schedule 2, Part 1) as it applies in London. In Hillingdon, a conservation area, Article 4 direction or listed status changes the route — the panels above show what is designated, and the address check confirms what applies at your property.
How much does a side return extension cost in Hillingdon?
| Cost per m² (low) | £3,200 |
| Cost per m² (expected) | £4,000 |
| Cost per m² (high — wrap-around, conservation spec) | £4,800+ |
| Typical project (9–15m² incl. structural opening) | £45,000 – £110,000 |
| Professional fees, surveys, party wall (add) | 10–18% of build |
Side returns price higher per m² than plain rear extensions because steelwork, underpinning the party wall and roof glazing are spread over fewer metres. Indicative ranges from real project data; VAT excluded.
Realistic timeline
| Design and drawings | 4–8 weeks |
| Planning decision | 8–12 weeks (8-week statutory target) |
| Party wall award (boundary wall works) | 6–10 weeks (parallel) |
| Build | 3–4 months |
What catches people out in Hillingdon
Party wall procedure on a shared flank is unavoidable. Do not design as if every Hillingdon plot keeps side-extension permitted development.
Postcode districts in Hillingdon
UB10 covers Hillingdon village and eastern Uxbridge — the Hillingdon Village conservation area among them.
UB10 — Hillingdon & Uxbridge →UB8 is Uxbridge — the Old Uxbridge / Windsor Street and Uxbridge Moor conservation areas and the Grand Union Canal.
UB8 — Uxbridge →HA4 covers Ruislip and Eastcote — the Ruislip Village, Eastcote Village and Eastcote Park Estate conservation areas, with Ruislip Woods beyond.
HA4 — Ruislip & Eastcote →HA6 is Northwood — the Frithwood and Green Lane conservation areas and the wooded, higher-value streets on the borough's northern edge.
HA6 — Northwood →UB7 covers West Drayton and Harmondsworth — the West Drayton Green and Harmondsworth Village conservation areas (the latter with its medieval tithe barn), near Heathrow and the Colne Valley Green Belt.
UB7 — West Drayton & Harmondsworth →UB3 is Hayes in Hillingdon — industrial-edge and suburban streets with regeneration pockets.
UB3 — Hayes →UB4 covers Yeading and the Hayes end of Hillingdon — suburban plots with more side access than inner terraces.
UB4 — Yeading & Hayes end →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.
UB9 — Harefield & Denham →Side return extension in Hillingdon, asked straight
Is a side return permitted development in Hillingdon?
How much does a side return cost?
What do officers focus on?
Will I need a party wall agreement?
Does a neighbour's consent help?
What applies at your address?
Borough-level rules only narrow it down. Enter a Hillingdon postcode for the live constraint check — conservation area, Article 4 and sold-price comparables, cited to source.
Need it in writing for one address? A planning permission report for a Hillingdon property — from £59, or surveyor-reviewed from £295.
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.