Where in Hillingdon does a rear dormer actually get determined?
District by district through Hillingdon: the stock behind each one, and who determines an application coming from it. Fees below are 2026 England statutory rates.
| Postcode | Area | Dominant stock | What it means for a rear dormer |
|---|
| HA4 | Ruislip | 1930s semi-detached, Tudor cottages | HA4 covers Ruislip only; Hillingdon Council handles the rear dormer. |
| HA5 | Pinner / Eastcote | Tudor fragments, Edwardian villas, 1930s semi-detached | HA5 straddles Pinner and Eastcote, and with them the line between Hillingdon and Harrow. Which council determines a dormer here follows the address, never the district. |
| HA6 | Northwood | 1930s detached, Edwardian villas | A rear dormer 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 | Hayes / Harlington sits wholly inside UB3, so Hillingdon Council validates every rear dormer submitted from an UB3 address. |
| UB4 | Hayes / Yeading | 1930s semi-detached, post-war estates | UB4 is Hayes and Yeading, wholly inside the borough, so Hillingdon Council determines a dormer application from any address in it. |
| UB7 | West Drayton / Sipson / Harmondsworth | 1930s semi-detached, post-war | West Drayton / Sipson / Harmondsworth sits wholly inside UB7, so Hillingdon Council validates every rear dormer submitted from an UB7 address. |
| UB8 | Uxbridge / Cowley | Georgian fragments, 1930s semi-detached, post-war flats | UB8 covers Uxbridge and Cowley, all of it Hillingdon. Conservation boundaries inside it are drawn street by street, not around the postcode. |
| UB9 | Denham / Harefield | Tudor and Georgian fragments, 1930s semi-detached | Check the county line before a UB9 dormer is drawn. The code reaches over both Harefield, which is Greater London and therefore Hillingdon, and Denham, which is Buckinghamshire. A rear dormer in Denham is assessed by Buckinghamshire Council and one in Harefield by Hillingdon. Heritage designations stop at the same boundary, so the map that governs a scheme is whichever authority is deciding it. |
How does a rear dormer differ street by street across Hillingdon?
Ridge height, rafter depth and how far the roof runs back all vary between Hillingdon streets, and every one of them decides how much dormer you can actually get out of the space.
- West Drayton (UB7) — 1930s semi-detached defines West Drayton, where 1930s semi-detached, post-war set what a rear dormer can do. Hip-to-gable plus rear dormer is the standard sequence on these 1930s semis across UB7. Any West Drayton rear dormer is validated by Hillingdon Council, with West Drayton station the usual West Drayton reference point on the site plan.
- Ickenham (UB10) — 1930s semi-detached, village conservation defines Ickenham, where 1930s semi-detached, tudor fragments set what a rear dormer can do. Hip-to-gable plus rear dormer is the standard sequence on these 1930s semis across UB10. Any Ickenham rear dormer is validated by Hillingdon Council, with Ickenham Village the usual Ickenham reference point on the site plan.
- Harefield (UB9) — rear dormer work in Harefield means tudor and georgian fragments, 1930s semi-detached. Harefield is village conservation, rural fringe. A dormer on a Georgian roof has to sit behind the parapet line to stand any chance of consent throughout UB9. Hillingdon Council decides the Harefield application, and Harefield Hospital anchors the Harefield location plan.
- Yiewsley (UB7) — rear dormer work in Yiewsley means 1930s semi-detached. Yiewsley is 1930s semi-detached. Hip-to-gable plus rear dormer is the standard sequence on these 1930s semis throughout UB7. Hillingdon Council decides the Yiewsley application, and Yiewsley High Street anchors the Yiewsley location plan.
- Eastcote (HA5) — a rear dormer in Eastcote starts from 1930s semi-detached, and Eastcote reads as 1930s semi-detached. Hip-to-gable plus rear dormer is the standard sequence on these 1930s semis in HA5. Hillingdon Council assesses Eastcote rear dormers against its own Eastcote character guidance, and the location plan we draw for Eastcote references Eastcote Tube.
- Hillingdon (UB10) — a rear dormer in Hillingdon starts from 1930s semi-detached, and Hillingdon reads as 1930s semi-detached, post-war. Hip-to-gable plus rear dormer is the standard sequence on these 1930s semis in UB10. Hillingdon Council assesses Hillingdon rear dormers against its own Hillingdon character guidance, and the location plan we draw for Hillingdon references Hillingdon Tube.
- Uxbridge (UB8) — rear dormer work in Uxbridge means georgian fragments, 1930s semi-detached, post-war flats. Uxbridge is Georgian centre, 1930s residential. A dormer on a Georgian roof has to sit behind the parapet line to stand any chance of consent throughout UB8. Hillingdon Council decides the Uxbridge application, and Uxbridge High Street anchors the Uxbridge location plan.
Does Hillingdon planning policy restrict a rear dormer?
Hillingdon conservation designations: 29 in all, Northwood, Harefield and Ickenham among them. Designation removes the permitted development route, so a rear dormer becomes a householder application rather than a prior approval. The householder application fee in England is £548, against an eight-week target. The fee for a larger householder prior approval is £249, on a six-week clock. Nothing published ranks one Hillingdon designation as tougher than another, so what matters is the boundary rather than the name attached to it.
Article 4 and your Hillingdon rear dormer: Hillingdon Council has made no borough-wide direction, so permitted development for a rear dormer in Hillingdon generally survives outside Hillingdon conservation areas and listed curtilages. A Lawful Development Certificate at £274 is how a HA4 owner records that a rear dormer was lawful.
What Hillingdon is built from: 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. That mix decides the rear dormer route in Hillingdon more than the postcode does, and it is what a Hillingdon Council case officer reads first. A householder application costs £548 paid to Hillingdon Council direct, with 8 weeks to a decision once validated.
Who decides a rear dormer on the edge of Hillingdon?
- Harrow — the Harrow boundary runs against Hillingdon, so a rear dormer a street from Hillingdon is decided by Harrow Council instead. Harrow runs 29 conservation areas across HA1 and its neighbours, which is why rear dormers priced for Hillingdon are re-checked against Harrow policy whenever the Hillingdon address sits on that edge.
- Ealing — adjoining Hillingdon, with 30 conservation areas centred on W3. A rear dormer on the far side of the Hillingdon line is determined by Ealing Council, so the Hillingdon quote for rear dormers is checked against Ealing guidance before it is issued.
- Hounslow — the Hounslow boundary runs against Hillingdon, so a rear dormer a street from Hillingdon is decided by Hounslow Council instead. Hounslow runs 30 conservation areas across W3 and its neighbours, which is why rear dormers priced for Hillingdon are re-checked against Hounslow policy whenever the Hillingdon address sits on that edge.
Sources for this Hillingdon rear dormer 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.
