Which Hillingdon postcodes does this house extension service cover?
The Hillingdon postcode districts we cover, what was mostly built in each, and who signs off an extension there. Charges shown are the 2026 statutory application fees, quite separate from the drawing fee we quote you.
| Postcode | Area | Dominant stock | What it means for a house extension |
|---|
| HA6 | Northwood | 1930s detached, Edwardian villas | A house extension at an HA6 address in Northwood is determined by Hillingdon Council under its own Local Plan policies for Northwood. |
| UB3 | Hayes / Harlington | 1930s semi-detached, post-war estates | UB3 is Hayes and Harlington, all of it in Hillingdon. Proximity to Heathrow does real work in this district: glazing specification and mechanical ventilation get read closely on any new habitable room, and a scheme whose comfort case depends on opening a window is harder to defend here than three miles north. |
| UB4 | Hayes / Yeading | 1930s semi-detached, post-war estates | UB4 takes in Hayes and Yeading and sits wholly inside the borough, so Hillingdon determines everything submitted from it. Plots here are deep and the stock is mostly inter-war and post-war semi-detached, so a single-storey rear extension tends to run out of appetite before it runs out of permitted depth. |
| UB7 | West Drayton / Sipson / Harmondsworth | 1930s semi-detached, post-war | West Drayton / Sipson / Harmondsworth sits wholly inside UB7, so Hillingdon Council validates every house extension submitted from an UB7 address. |
| UB8 | Uxbridge / Cowley | Georgian fragments, 1930s semi-detached, post-war flats | UB8 covers Uxbridge and Cowley. The older cottage terraces around the town centre fall inside designated areas where permitted development is curtailed, so an identical rear extension can be a £274 certificate on one street and a £548 householder application on the next. We check the designation boundary against the address before quoting. |
| UB9 | Denham / Harefield | Tudor and Georgian fragments, 1930s semi-detached | UB9 is the district to check before you assume anything. Harefield lies in Hillingdon; Denham does not, and sits across the county boundary in Buckinghamshire under a different local plan and a different validation list. Much of the district is Green Belt as well, where the question becomes whether the addition is proportionate to the original dwelling rather than whether it meets householder policy. |
| UB10 | Hillingdon / Ickenham | 1930s semi-detached, Tudor fragments | Hillingdon / Ickenham sits wholly inside UB10, so Hillingdon Council validates every house extension submitted from an UB10 address. |
| UB11 | Stockley Park | Inter-war construction is the defining feature: 29.8% of Hillingdon's 118,250 dwellings were built between 1930 and 1939, while only 1.8% of them are Victorian or older (VOA council tax stock by build period, dated 31 March 2025). Green Belt occupies the north of the borough, Heathrow shaped the south, and the Victorian cottage stock is concentrated in the Uxbridge and Ruislip village cores. | A house extension at an UB11 address in Stockley Park is determined by Hillingdon Council under its own Local Plan policies for Stockley Park. |
What changes about a house extension in each part of Hillingdon?
Plot depth is the variable that moves most across Hillingdon — long rear gardens on the inter-war estates, far tighter ground in the village cores — and it settles more about an extension than borough policy ever does.
- Hayes (UB3, UB4) — 1930s semi-detached, post-war defines Hayes, where 1930s semi-detached, post-war estates set what a house extension can do. 1930s semis here have the deepest rear gardens in the area across UB3. Any Hayes house extension is validated by Hillingdon Council, with Hayes & Harlington the usual Hayes reference point on the site plan.
- West Drayton (UB7) — a house extension in West Drayton starts from 1930s semi-detached, post-war, and West Drayton reads as 1930s semi-detached. 1930s semis here have the deepest rear gardens in the area in UB7. Hillingdon Council assesses West Drayton house extensions against its own West Drayton character guidance, and the location plan we draw for West Drayton references West Drayton station.
- Ickenham (UB10) — 1930s semi-detached, village conservation defines Ickenham, where 1930s semi-detached, tudor fragments set what a house extension can do. 1930s semis here have the deepest rear gardens in the area across UB10. Any Ickenham house extension is validated by Hillingdon Council, with Ickenham Village the usual Ickenham reference point on the site plan.
- Harefield (UB9) — a house extension in Harefield starts from tudor and georgian fragments, 1930s semi-detached, and Harefield reads as village conservation, rural fringe. Georgian rear elevations here are usually the listed or locally listed face of the building in UB9. Hillingdon Council assesses Harefield house extensions against its own Harefield character guidance, and the location plan we draw for Harefield references Harefield Hospital.
- Yiewsley (UB7) — 1930s semi-detached defines Yiewsley, where 1930s semi-detached set what a house extension can do. 1930s semis here have the deepest rear gardens in the area across UB7. Any Yiewsley house extension is validated by Hillingdon Council, with Yiewsley High Street the usual Yiewsley reference point on the site plan.
- Eastcote (HA5) — house extension work in Eastcote means 1930s semi-detached. Eastcote is 1930s semi-detached. 1930s semis here have the deepest rear gardens in the area throughout HA5. Hillingdon Council decides the Eastcote application, and Eastcote Tube anchors the Eastcote location plan.
- Hillingdon (UB10) — house extension work in Hillingdon means 1930s semi-detached. Hillingdon is 1930s semi-detached, post-war. 1930s semis here have the deepest rear gardens in the area throughout UB10. Hillingdon Council decides the Hillingdon application, and Hillingdon Tube anchors the Hillingdon location plan.
How do conservation areas and Article 4 affect a house extension in Hillingdon?
Conservation areas covering Hillingdon: Hillingdon Council runs 29, and Ruislip Village, Northwood, Harefield are the ones Hillingdon owners meet most. A house extension 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 Harefield a house extension is judged on the street elevation first.
No blanket Article 4 over Hillingdon: Hillingdon Council has not withdrawn permitted development across Hillingdon, so a house extension outside a Hillingdon conservation area usually keeps it. The £274 Lawful Development Certificate is still the document a HA4 owner wants on file.
The building fabric around 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. Largest outer west London borough; significant Green Belt; Heathrow noise contours affect planning decisions in Harmondsworth and Sipson. A house extension in Hillingdon is scoped against that stock first, because it decides whether the scheme runs as permitted development, a £274 Lawful Development Certificate, or a full £548 application to Hillingdon Council.
Which neighbouring authorities border Hillingdon?
- Harrow — adjoining Hillingdon, with 29 conservation areas centred on HA1. A house extension on the far side of the Hillingdon line is determined by Harrow Council, so the Hillingdon quote for house extensions is checked against Harrow guidance before it is issued.
- Ealing — cross the Hillingdon boundary and Ealing Council takes the house extension instead, applying 30 conservation areas of its own around W3. We re-price house extensions at the Hillingdon edge because Ealing policy and Hillingdon policy rarely align on house extension depth.
- Hounslow — cross the Hillingdon boundary and Hounslow Council takes the house extension instead, applying 30 conservation areas of its own around W3. We re-price house extensions at the Hillingdon edge because Hounslow policy and Hillingdon policy rarely align on house extension depth.
Sources for this Hillingdon house extension 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.
