Basement in City of London: Planning Permission Guide
What you need to know about basement extensions in City of London — planning requirements, costs, and professional guidance.
Based on 32 decided applications in City of London over 12 months (30 granted, 2 refused).
The City of London is almost entirely conservation area, with extensive listed building coverage reflecting centuries of heritage. Residential permitted development is extremely limited due to the dense mix of commercial and listed contexts. Any external alteration typically requires both full planning permission and listed building consent. The City Corporation maintains detailed design guidance for each conservation area.
Personalised odds
5 nearest comparables & refusal reasons for your address.
Get my report — £9See a sample →Recent basement decisions in City of London
The 5 most recent decided applications. Addresses redacted to postcode area.
Non-material amendment under Section 96a of the Town and Country Planning Act 1990 (as amended) to planning permission 22/00882/FULMAJ da…
Application under section 19 of the Planning (Listed Buildings and Conservation Areas) Act 1990 to vary condition 5 of Listed Building Co…
Consultation by London Borough of Tower Hamlets on an application for demolition of the existing building and erection of a new building …
Internal and external alterations including (i) replacement HVAC units to first floor roof (ii) replacement retractable awning at ground …
Continued temporary change of use of basement, part ground and first floor level from office (Class E) to use as construction welfare fac…
These are borough-wide. See the 5 nearest to your address.
Get my report — £9Permitted Development Rules
Basement excavation requires a full planning application.
Basement excavation does not have permitted development rights under Part 1 of the GPDO. A full planning application is always required.
Typical Costs in London
Basements are among the most expensive home improvement projects. Costs vary enormously depending on depth, ground conditions, and access.
Cost per m²
construction rate
Typical total
Based on 25–50 m²
Typically includes
Typically excludes
Basement projects are complex and costs vary enormously depending on depth, ground conditions, waterproofing, and access. Professional advice is essential.
Get a personalised cost estimate based on your actual basement dimensions.
Get my estimateWhich Professionals Do You Need?
Basement projects are complex and always require specialist professional input — an architect, structural engineer, and usually a party wall surveyor.
You'll need an architect, a structural engineer, and a party wall surveyor for this project.
Basement projects are complex and require specialist architectural and structural design.
Typical fee: £5,000–£15,000 (Full architectural service)
Basement excavation requires detailed structural engineering for underpinning, retaining walls, and waterproofing.
Typical fee: £2,000–£5,000
Basement excavation almost always triggers the Party Wall Act due to work near neighbouring foundations.
Typical fee: £700–£1,500 (per neighbour)
This guidance is based on a typical semi-detached house with no special constraints. Listed buildings, conservation areas, and attached properties may require additional professional input.
Find out exactly which professionals you need for your basement.
Get personalised guidanceConservation Areas & Listed Buildings
In conservation areas, basement applications receive additional scrutiny. The council will consider the impact on neighbouring properties and the character of the area.
Properties in conservation areas often have reduced permitted development rights. Some project types (like side extensions) lose PD rights entirely. An Article 4 Direction can remove additional PD rights.
Listed buildings (Grade I, II*, or II) have no permitted development rights at all. Any external alteration requires Listed Building Consent in addition to any planning permission. An architect experienced in heritage work is essential.
Check if your property is in a conservation area or has other planning constraints.
Check my propertyFrequently Asked Questions
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