Rear extension in City of London
Do you need planning permission for a rear extension in City of London?
Barely applies in practice. The City's homes are overwhelmingly listed flats — chiefly the Barbican and Golden Lane estates — with no permitted development rights, so any external alteration needs planning permission and almost always listed building consent. Conservation-area coverage is near-total. There is no ordinary householder rear-extension market here.
Barely applies — the City's homes are listed Barbican and Golden Lane flats with no PD rights, where listed building consent governs any change.
The Square Mile is a planning authority unlike any other in London: commercial-first, heritage-dense, with very little residential stock. Protected views of St Paul's and the Tower shape massing even where a residential alteration is contemplated. The City's Local Plan and estate management guidelines — not householder permitted development — are the operative regime.
What actually applies in City of London
Conservation areas in City of London
Real · planning.data.gov.ukEvery designated conservation area in City of London from the official dataset — inside one, permitted development narrows and design scrutiny rises.
- Bank
- Barbican and Golden Lane
- Bishopsgate
- Bow Lane
- Brewery
- Chancery Lane
- Charterhouse Square
- Creechurch
- Crescent
- Eastcheap
- Fenchurch Street Station
- Finsbury Circus
- Fleet Street
- Foster Lane
- Guildhall
- Laurence Poutney Hill
- Leadenhall Market
- Lloyd's Avenue
- New Broad Street
- Newgate Street
- Postman's Park
- Queen Street
- Smithfield
- St Helen's Place
- St Paul's Cathedral
- Temples
- Trinity Square
- Whitefriars
Source: planning.data.gov.uk · Open Government Licence. Boundaries are checked at address level by the area report.
Article 4 directions in City of London
Real · planning.data.gov.ukNo householder Article 4 geometry for the City of London appears in the national planning.data.gov.uk dataset, and the City is not an HMO-conversion borough. What constrains residential change here is the near-total conservation-area coverage and the very high concentration of listed buildings — including the Grade II–listed Barbican and Golden Lane estates — where listed building consent and conservation-area control, not Article 4 directions, are the operative regime. Check the City of London Local Plan and the relevant management guidelines.
Source: planning.data.gov.uk · Open Government Licence. Checked at address level by the area report.
Prices: HM Land Registry UK House Price Index, December 2025 · Open Government Licence.
The planning route — PD or permission?
Permitted development (GPDO Class A) covers single-storey rear extensions up to 3m beyond the original rear wall on attached houses and 4m on detached, with a maximum height of 4m. The 'larger home extension' route extends this to 6m/8m through prior approval with neighbour consultation — but that larger route is not available in conservation areas.
In conservation areas, the basic 3m/4m single-storey rear PD allowance usually survives — what conservation-area status removes is side extensions and two-storey rear extensions. An Article 4 direction can remove more, but Camden's directions in Hampstead and Belsize target front-and-side appearance (solar panels, window changes, boundary treatments), not the single-storey rear allowance. Flats have no PD rights at all. Two-storey rear extensions in conservation areas always need full permission.
Practical rule across London: check the address first. If a conservation area or Article 4 direction applies, budget for a full householder application decided on design, neighbour daylight (the 45-degree test) and materials.
Permitted development limits — rear extension
| Single-storey rear depth — attached house | 3m beyond the original rear wall |
| Single-storey rear depth — detached house | 4m beyond the original rear wall |
| Larger extension via prior approval | 6m attached / 8m detached — not in conservation areas |
| Maximum height (single storey) | 4m |
| Two-storey rear in a conservation area | Full planning permission required |
| Flats | No permitted development rights |
Limits summarise the General Permitted Development Order (Schedule 2, Part 1) as it applies in London. In City of London, a conservation area, Article 4 direction or listed status changes the route — the panels above show what is designated, and the address check confirms what applies at your property.
How much does a rear extension cost in City of London?
| Cost per m² (low — straightforward site) | £3,000 |
| Cost per m² (expected) | £3,800 |
| Cost per m² (high — conservation spec, hard access) | £4,600+ |
| Typical build cost (12–18m² single storey) | £36,000 – £83,000 |
| Professional fees, surveys, party wall (add) | 10–18% of build |
Indicative London ranges calibrated from real project data. Conservation-area specifications (matching stock brick, lime mortar, bespoke glazing) and restricted rear access are the two biggest cost drivers. VAT not included.
Realistic timeline
| Design and drawings | 4–8 weeks |
| Planning decision (full application) | 8–12 weeks (8-week statutory target) |
| Prior approval route, where available | 42 days |
| Party wall agreements | 4–10 weeks (parallel) |
| Build | 3–5 months |
What catches people out in City of London
Starting from a suburban rear-extension playbook is the wrong mental model. Confirm listing, conservation designation and freeholder or estate management rules before any design spend.
Postcode districts in City of London
EC2 holds the City's main residential community — the Grade II–listed Barbican and Golden Lane estates, within the Barbican and Golden Lane Conservation Area — alongside Bank, Guildhall and Moorgate.
EC2 — The Barbican & the City core →EC3 covers the eastern Square Mile toward Tower Hill and Aldgate, with commercial floorspace and limited residential stock.
EC3 — Tower Hill, Aldgate & the eastern City →EC4 runs from Fleet Street and the Temples to St Paul's and Blackfriars — one of the densest heritage cores in the country.
EC4 — Fleet Street, St Paul's & Blackfriars →EC2M is the office City.
EC2M — Liverpool Street & Broadgate →EC2V is the civic and banking heart of the Square Mile: Cheapside's retail frontage, Gresham Street's offices and the medieval street pattern threading behind them.
EC2V — Cheapside & Gresham Street →EC2Y is the exception in the City — a genuinely residential district.
EC2Y — The Barbican & Golden Lane →EC3A is the City's eastern edge around Aldgate and Houndsditch, where insurance and back-office floorspace fills most of the frontage.
EC3A — Aldgate & Houndsditch →EC3M is the insurance quarter — broking and underwriting floorspace along Fenchurch Street and Leadenhall Street, with tall towers rising between them.
EC3M — Fenchurch Street & Leadenhall →EC3N runs from the Minories down to Tower Hill, and it holds more housing than most of the Square Mile — flat conversions on the eastern streets plus newer apartment blocks, shading into St Katharine's, Wapping and Whitechapel across the Tower Hamlets line.
EC3N — Tower Hill & the Minories →EC3R covers the Monument, the lanes dropping south to Lower Thames Street and the riverside frontage beyond.
EC3R — Monument & Lower Thames Street →EC4A covers Fetter Lane, Shoe Lane and the streets climbing to Holborn Circus — legal, media and professional offices in post-war and modern blocks, with only a scattering of homes on upper floors.
EC4A — Fetter Lane & Holborn Circus →EC4M is the ground around St Paul's — Ludgate Hill, Paternoster, Ave Maria Lane and the lanes running east toward Bread Street.
EC4M — St Paul's & Ludgate Hill →EC4R is the slope between Cannon Street and the river: Dowgate Hill, Cousin Lane, College Hill and the lanes dropping to Upper Thames Street.
EC4R — Cannon Street & the Dowgate riverside →EC4V runs from Blackfriars along Queen Victoria Street to Queenhithe and the old wharf frontages rebuilt as offices.
EC4V — Blackfriars & Queenhithe →EC4Y is Fleet Street, Whitefriars, Carmelite Street and the Temple — the old newspaper quarter, now offices, wrapped around the Inns of Court.
EC4Y — Fleet Street & the Temple →Rear extension in City of London, asked straight
Can I build a rear extension in the City of London?
How much would a rear extension cost if it were possible?
Do flats have permitted development rights?
What documents should I read first?
Is there an Article 4 householder regime here?
What applies at your address?
Borough-level rules only narrow it down. Enter a City of London postcode for the live constraint check — conservation area, Article 4 and sold-price comparables, cited to source.
Need it in writing for one address? A planning permission report for a City of London property — from £59, or surveyor-reviewed from £295.
Planning Permission Checker provides planning and cost intelligence for early feasibility only. It is not legal, planning, valuation, architectural, structural, or surveying advice. All estimates are indicative and must be verified by qualified professionals before purchase, design, planning submission, or construction.
Cost estimates are indicative only — not a quotation. Final price depends on survey, specification, structure, access, party wall matters, VAT, professional fees, and contractor availability.
Planning outcomes are not guaranteed. Local planning authorities make final decisions.