The Edwardian villas of Chiswick and basements in Hounslow

Which Hounslow postcodes does this basement extension service cover?

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

Which Hounslow neighbourhoods suit a basement extension best?

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

• Chiswick (W4) — a basement extension in Chiswick starts from edwardian villas, victorian terraces, and Chiswick reads as Edwardian villas, conservation. Victorian cellars here convert without planning permission when the footprint and external appearance are unchanged in W4. Hounslow Council assesses Chiswick basement extensions against its own Chiswick character guidance, and the location plan we draw for Chiswick references Chiswick House.
• Brentford (TW8) — Georgian fragments, riverside new-build defines Brentford, where georgian fragments, victorian terraces, new-build set what a basement extension can do. Georgian houses here already have a vault and a lower-ground floor across TW8. Any Brentford basement extension is validated by Hounslow Council, with Kew Bridge the usual Brentford reference point on the site plan.
• Isleworth (TW7) — a basement extension in Isleworth starts from georgian and victorian terraces, and Isleworth reads as Georgian and Victorian terraces. Georgian houses here already have a vault and a lower-ground floor in TW7. Hounslow Council assesses Isleworth basement extensions against its own Isleworth character guidance, and the location plan we draw for Isleworth references Old Isleworth.
• Hounslow (TW3) — a basement extension in Hounslow starts from 1930s semi-detached, post-war flats, and Hounslow reads as 1930s semi-detached, post-war flats. 1930s houses were built without cellars in TW3. Hounslow Council assesses Hounslow basement extensions against its own Hounslow character guidance, and the location plan we draw for Hounslow references Hounslow Central.
• Feltham (TW13) — a basement extension in Feltham starts from 1930s semi-detached, post-war estates, and Feltham reads as 1930s semi-detached, post-war estates. 1930s houses were built without cellars in TW13. Hounslow Council assesses Feltham basement extensions against its own Feltham character guidance, and the location plan we draw for Feltham references Feltham station.
• Hanworth (TW13) — basement extension work in Hanworth means 1930s semi-detached. Hanworth is 1930s semi-detached. 1930s houses were built without cellars throughout TW13. Hounslow Council decides the Hanworth application, and Hanworth Park anchors the Hanworth location plan.
• Turnham Green (W4) — a basement extension in Turnham Green starts from edwardian villas, and Turnham Green reads as Edwardian villas, conservation. Edwardian houses rarely have a usable cellar in W4. Hounslow Council assesses Turnham Green basement extensions against its own Turnham Green character guidance, and the location plan we draw for Turnham Green references Turnham Green.

What local planning policy applies to a basement extension in Hounslow?

Hounslow conservation designations: there are 30 across Hounslow Council, Brentford, Chiswick, Bedford Park among them. Designation costs a Hounslow owner the permitted-development route: a basement extension then needs a £548 householder application over 8 weeks, in place of the £249 prior approval route that takes 6 weeks. Old Isleworth is the Hounslow designation that most often changes a basement extension design.

Article 4 and your Hounslow basement extension: Hounslow Council has made no borough-wide direction, so permitted development for a basement extension in Hounslow generally survives outside Hounslow conservation areas and listed curtilages. A Lawful Development Certificate at £274 is how a W4 owner records that a basement extension was lawful.

What Hounslow is built from: Edwardian villas in Chiswick and Turnham Green; Georgian in Isleworth; 1930s semi-detached in Hounslow and Feltham; riverside new-build in Brentford. Chiswick is one of west London's most conservation-controlled areas; outer Hounslow is permissive suburban. That mix decides the basement extension route in Hounslow more than the postcode does.

Which neighbouring authorities border Hounslow?

• Hillingdon — adjoining Hounslow, with 29 conservation areas centred on HA4. A basement extension on the far side of the Hounslow line is determined by Hillingdon Council, so the Hounslow quote for basement extensions is checked against Hillingdon guidance before it is issued.
• Ealing — the Ealing boundary runs against Hounslow, so a basement extension a street from Hounslow is decided by Ealing Council instead. Ealing runs 30 conservation areas across W3 and its neighbours, which is why basement extensions priced for Hounslow are re-checked against Ealing policy whenever the Hounslow address sits on that edge.
• Hammersmith and Fulham — the Hammersmith and Fulham boundary runs against Hounslow, so a basement extension a street from Hounslow is decided by Hammersmith & Fulham Council instead. Hammersmith and Fulham runs 45 conservation areas across W6 and its neighbours, which is why basement extensions priced for Hounslow are re-checked against Hammersmith and Fulham policy whenever the Hounslow address sits on that edge.
• Richmond upon Thames — the Richmond upon Thames boundary runs against Hounslow, so a basement extension a street from Hounslow is decided by Richmond Council instead. Richmond upon Thames runs 72 conservation areas across SW13 and its neighbours, which is why basement extensions priced for Hounslow are re-checked against Richmond upon Thames policy whenever the Hounslow address sits on that edge.

Sources for this Hounslow basement 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.