Basement Conversion Drawings in Hillingdon

Which postcode districts around Hillingdon do we cover for basement conversion work?

Every Hillingdon postcode district we draw in, the stock that dominates it and the authority that validates a basement conversion there. Hillingdon fees below are the statutory England rates for 2026, not basement conversion estimates.

Which Hillingdon neighbourhoods suit a basement conversion best?

Roof pitch, wall build-up and plot depth change every few Hillingdon streets, and each one changes what a basement conversion can achieve at that address.

• Yiewsley (UB7) — a basement conversion in Yiewsley starts from 1930s semi-detached, and Yiewsley reads as 1930s semi-detached. 1930s houses were built without cellars in UB7. Hillingdon Council assesses Yiewsley basement conversions against its own Yiewsley character guidance, and the location plan we draw for Yiewsley references Yiewsley High Street.
• Eastcote (HA5) — 1930s semi-detached defines Eastcote, where 1930s semi-detached set what a basement conversion can do. 1930s houses were built without cellars across HA5. Any Eastcote basement conversion is validated by Hillingdon Council, with Eastcote Tube the usual Eastcote reference point on the site plan.
• Hillingdon (UB10) — a basement conversion in Hillingdon starts from 1930s semi-detached, and Hillingdon reads as 1930s semi-detached, post-war. 1930s houses were built without cellars in UB10. Hillingdon Council assesses Hillingdon basement conversions against its own Hillingdon character guidance, and the location plan we draw for Hillingdon references Hillingdon Tube.
• Uxbridge (UB8) — Georgian centre, 1930s residential defines Uxbridge, where georgian fragments, 1930s semi-detached, post-war flats set what a basement conversion can do. Georgian houses here already have a vault and a lower-ground floor across UB8. Any Uxbridge basement conversion is validated by Hillingdon Council, with Uxbridge High Street the usual Uxbridge reference point on the site plan.
• Ruislip (HA4) — a basement conversion in Ruislip starts from 1930s semi-detached, tudor cottages, and Ruislip reads as 1930s semi-detached, Tudor fragments. 1930s houses were built without cellars in HA4. Hillingdon Council assesses Ruislip basement conversions against its own Ruislip character guidance, and the location plan we draw for Ruislip references Ruislip Lido.
• Northwood (HA6) — a basement conversion in Northwood starts from 1930s detached, edwardian villas, and Northwood reads as 1930s detached and semi-detached. Edwardian houses rarely have a usable cellar in HA6. Hillingdon Council assesses Northwood basement conversions against its own Northwood character guidance, and the location plan we draw for Northwood references Northwood Hills.
• Hayes (UB3, UB4) — 1930s semi-detached, post-war defines Hayes, where 1930s semi-detached, post-war estates set what a basement conversion can do. 1930s houses were built without cellars across UB3. Any Hayes basement conversion is validated by Hillingdon Council, with Hayes & Harlington the usual Hayes reference point on the site plan.

How do conservation areas and Article 4 affect a basement conversion in Hillingdon?

Hillingdon conservation designations: there are 29 across Hillingdon Council, Uxbridge, Ruislip Village, Northwood among them. Designation costs a Hillingdon owner the permitted-development route: a basement conversion then needs a £548 householder application over 8 weeks, in place of the £249 prior approval route that takes 6 weeks. Harefield is the Hillingdon designation that most often changes a basement conversion design.

No blanket Article 4 over Hillingdon: Hillingdon Council has not withdrawn permitted development across Hillingdon, so a basement conversion 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 basement conversion 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.

What happens if a Hillingdon property sits on a boundary?

• Harrow — cross the Hillingdon boundary and Harrow Council takes the basement conversion instead, applying 29 conservation areas of its own around HA1. We re-price basement conversions at the Hillingdon edge because Harrow policy and Hillingdon policy rarely align on basement conversion depth.
• Ealing — adjoining Hillingdon, with 30 conservation areas centred on W3. A basement conversion on the far side of the Hillingdon line is determined by Ealing Council, so the Hillingdon quote for basement conversions is checked against Ealing guidance before it is issued.
• Hounslow — the Hounslow boundary runs against Hillingdon, so a basement conversion a street from Hillingdon is decided by Hounslow Council instead. Hounslow runs 30 conservation areas across W3 and its neighbours, which is why basement conversions priced for Hillingdon are re-checked against Hounslow policy whenever the Hillingdon address sits on that edge.

Sources for this Hillingdon basement 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.