Basement Conversion Drawings in Westminster

Where in Westminster does a basement conversion actually get determined?

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

What changes about a basement conversion in each part of Westminster?

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

• Marylebone (W1U, W1G, W1H) — basement conversion work in Marylebone means georgian terraces, edwardian mansion blocks. Marylebone is Georgian and Victorian terraces, mansion blocks. Georgian houses here already have a vault and a lower-ground floor throughout W1U. Westminster City Council decides the Marylebone application, and Marylebone High Street anchors the Marylebone location plan.
• Pimlico (SW1V) — a basement conversion in Pimlico starts from regency terraces, post-war estates, and Pimlico reads as Regency stucco terraces, grid plan. Post-war slab foundations make basements here expensive and rarely viable in SW1V. Westminster City Council assesses Pimlico basement conversions against its own Pimlico character guidance, and the location plan we draw for Pimlico references Tate Britain.
• Soho (W1D, W1F) — a basement conversion in Soho starts from georgian terraces, mixed-use, and Soho reads as Georgian fragments, mixed-use. Georgian houses here already have a vault and a lower-ground floor in W1D. Westminster City Council assesses Soho basement conversions against its own Soho character guidance, and the location plan we draw for Soho references Soho Square.
• Covent Garden (WC2E, WC2H) — basement conversion work in Covent Garden means georgian terraces, conversions. Covent Garden is Georgian piazza, listed buildings. Georgian houses here already have a vault and a lower-ground floor throughout WC2E. Westminster City Council decides the Covent Garden application, and Royal Opera House anchors the Covent Garden location plan.
• St John's Wood (NW8) — a basement conversion in St John's Wood starts from victorian villas, mansion blocks, and St John's Wood reads as Victorian villas, mansion blocks. Victorian cellars here convert without planning permission when the footprint and external appearance are unchanged in NW8. Westminster City Council assesses St John's Wood basement conversions against its own St John's Wood character guidance, and the location plan we draw for St John's Wood references Lord's Cricket Ground.
• Bayswater (W2) — a basement conversion in Bayswater starts from victorian stucco terraces, and Bayswater reads as Victorian stucco terraces. Victorian cellars here convert without planning permission when the footprint and external appearance are unchanged in W2. Westminster City Council assesses Bayswater basement conversions against its own Bayswater character guidance, and the location plan we draw for Bayswater references Hyde Park.
• Paddington (W2) — a basement conversion in Paddington starts from regency terraces, modern apartments, and Paddington reads as Regency and Victorian terraces, canal-side regen. Modern foundations here are usually raft or piled in W2. Westminster City Council assesses Paddington basement conversions against its own Paddington character guidance, and the location plan we draw for Paddington references Paddington Basin.

Does Westminster planning policy restrict a basement conversion?

Conservation areas covering Westminster: Westminster City Council runs 56, and Covent Garden, St John's Wood, Mayfair are the ones Westminster owners meet most. A basement conversion inside a Westminster conservation area loses permitted development, so the Westminster submission is a householder application at £548 decided in 8 weeks — not a £249 prior approval decided in 6 weeks. In Mayfair a basement conversion is judged on the street elevation first.

What Article 4 removes near Westminster: Multiple Article 4 Directions — office-to-residential restrictions, HMO conversions, retail to residential in shopping zones. Before pricing a basement conversion we check whether the NW8 address is inside the mapped area, because Westminster City Council draws the Westminster boundary street by street rather than across the whole of Westminster.

Westminster below-ground policy: Westminster basement policy restricts to single-storey, typically under 50% of rear garden footprint; lightwells and rooflights strictly controlled in conservation areas. Any basement conversion in Westminster that goes below existing foundations triggers two months notice under section 6 of the Party Wall etc. Act 1996, and Westminster City Council will want the NW8 ground and groundwater position set out.

Westminster housing stock: Grand Georgian and Regency terraces in Belgravia and Pimlico; Victorian and Edwardian mansion blocks; heritage-rich townhouses throughout; very high listed building density. Heritage-first planning approach; listed buildings on almost every street; basement and rear extension policies particularly strict. Read that before choosing a basement conversion route in Westminster — construction, not postcode, sets what is achievable. Westminster City Council charges £548 for a householder application and has 8 weeks to determine it.

Who decides a basement conversion on the edge of Westminster?

• Lambeth — adjoining Westminster, with 64 conservation areas centred on SE1. A basement conversion on the far side of the Westminster line is determined by Lambeth Council, so the Westminster quote for basement conversions is checked against Lambeth guidance before it is issued.
• City of London — cross the Westminster boundary and City of London Corporation takes the basement conversion instead, applying 27 conservation areas of its own around EC1. We re-price basement conversions at the Westminster edge because City of London policy and Westminster policy rarely align on basement conversion depth.
• Camden — adjoining Westminster, with 40 conservation areas centred on NW1. A basement conversion on the far side of the Westminster line is determined by Camden Council, so the Westminster quote for basement conversions is checked against Camden guidance before it is issued.
• Kensington and Chelsea — the Kensington and Chelsea boundary runs against Westminster, so a basement conversion a street from Westminster is decided by RBKC Planning instead. Kensington and Chelsea runs 38 conservation areas across SW1 and its neighbours, which is why basement conversions priced for Westminster are re-checked against Kensington and Chelsea policy whenever the Westminster address sits on that edge.

Sources for this Westminster 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.