Basement in Bromley: Planning Permission Guide
What you need to know about basement extensions in Bromley — planning requirements, costs, and professional guidance.
Based on 35 decided applications in Bromley over 24 months (24 granted, 11 refused).
Bromley is one of London's largest and greenest boroughs, with substantial Green Belt in the south and east around Biggin Hill, Downe, Orpington rural areas, and parts of the North Downs. Conservation areas include Keston, Chislehurst, Shortlands, Farnborough Village, and Hayes. Listed buildings cluster around Down House (Darwin's home), Chislehurst, and Farnborough. Properties in Green Belt locations face tight restrictions on extension size and outbuilding coverage.
Personalised odds
5 nearest comparables & refusal reasons for your address.
Get my report — £9See a sample →Recent basement decisions in Bromley
The 5 most recent decided applications. Addresses redacted to postcode area.
Removal of existing air handling heating/cooling unit and installation of replacement plant comprising 4 no. external condenser units to …
To carry out excavations and potentially root-pruning within the nominal calculated Root Protection Areas of the x3 Pine trees located at…
Demolition of the existing dwelling and erection of a four storey (including basements) building to create 4 self-contained residential f…
Phased mixed-use redevelopment of the site comprising: Demolition of all existing buildings/structures, site preparation, and enabling wo…
Erection of detached part single storey, part two storey 3 bedroom self/custom-build dwelling (including basement) on land adjacent to Sw…
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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