House Extension Drawings in City of London

Which City of London postcodes does this house extension service cover?

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

What changes about a house extension in each part of City of London?

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

• Barbican (EC2Y) — a house extension in Barbican starts from listed brutalist apartments (barbican estate), and Barbican reads as Brutalist listed estate. Post-war houses on these estates often sit under an estate management scheme in EC2Y. City of London Corporation assesses Barbican house extensions against its own Barbican character guidance, and the location plan we draw for Barbican references Barbican Centre.
• Smithfield (EC1A) — a house extension in Smithfield starts from mostly commercial, residential lofts, and Smithfield reads as Georgian and Victorian commercial. The side-return infill is the classic move on these Victorian terraces — 3 m of permitted development depth plus the width of the original side passage in EC1A. City of London Corporation assesses Smithfield house extensions against its own Smithfield character guidance, and the location plan we draw for Smithfield references Smithfield Market.
• Fleet Street (EC4) — house extension work in Fleet Street means mostly commercial, residential conversions. Fleet Street is Georgian and Victorian commercial. The side-return infill is the classic move on these Victorian terraces — 3 m of permitted development depth plus the width of the original side passage throughout EC4. City of London Corporation decides the Fleet Street application, and Royal Courts of Justice anchors the Fleet Street location plan.
• St Paul's (EC4M) — Listed heritage commercial core defines St Paul's, where mostly commercial, listed residential set what a house extension can do. The side-return infill is the classic move on these Victorian terraces — 3 m of permitted development depth plus the width of the original side passage across EC4M. Any St Paul's house extension is validated by City of London Corporation, with St Paul's Cathedral the usual St Paul's reference point on the site plan.

How do conservation areas and Article 4 affect a house extension in City of London?

City of London conservation designations: there are 27 across City of London Corporation, St Paul's, Barbican, Smithfield among them. Designation costs a City of London owner the permitted-development route: a house extension then needs a £548 householder application over 8 weeks, in place of the £249 prior approval route that takes 6 weeks. Barbican is the City of London designation that most often changes a house extension design.

What Article 4 removes near City of London: Multiple Article 4 Directions around office-to-residential, demolition, and shopfront changes. Before pricing a house extension we check whether the EC1A address is inside the mapped area, because City of London Corporation draws the City of London boundary street by street rather than across the whole of City of London.

City of London housing stock: Very limited residential — Barbican Estate (listed post-war), Golden Lane Estate, modern luxury flats; overwhelmingly commercial. Overwhelmingly commercial; residential planning extremely constrained; one of the two highest listed-building densities in London. Read that before choosing a house extension route in City of London — construction, not postcode, sets what is achievable. City of London Corporation charges £548 for a householder application and has 8 weeks to determine it.

Who decides a house extension on the edge of City of London?

• Southwark — adjoining City of London, with 43 conservation areas centred on SE1. A house extension on the far side of the City of London line is determined by Southwark Council, so the City of London quote for house extensions is checked against Southwark guidance before it is issued.
• Westminster — the Westminster boundary runs against City of London, so a house extension a street from City of London is decided by Westminster City Council instead. Westminster runs 56 conservation areas across SW1 and its neighbours, which is why house extensions priced for City of London are re-checked against Westminster policy whenever the City of London address sits on that edge.
• Camden — adjoining City of London, with 40 conservation areas centred on NW1. A house extension on the far side of the City of London line is determined by Camden Council, so the City of London quote for house extensions is checked against Camden guidance before it is issued.
• Islington — adjoining City of London, with 40 conservation areas centred on N1. A house extension on the far side of the City of London line is determined by Islington Council, so the City of London quote for house extensions is checked against Islington guidance before it is issued.

Sources for this City of London 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.