Basement in Lewisham: Planning Permission Guide
What you need to know about basement extensions in Lewisham — planning requirements, costs, and professional guidance.
Based on 39 decided applications in Lewisham over 24 months (31 granted, 8 refused).
Lewisham has conservation areas in Blackheath, Telegraph Hill, Brockley, Lee Manor, and Forest Hill. Article 4 Directions restrict window and door alterations in several Victorian conservation areas. The borough mixes dense inner-city housing in the north with more suburban character in the south. Flood zones along the Ravensbourne and Quaggy rivers restrict outbuilding classes for riverside properties.
Recent basement decisions in Lewisham
The 5 most recent decided applications. Addresses redacted to postcode area.
Application for a Lawful Development Certificate (Existing) submitted under Section (191) of the Town & Country Planning Act 1990 (as ame…
Listed Building Consent for the internal alterations and external works to the existing public house to facilitate its continued use as a…
Change of use and alterations to the existing basement, formation of lightwells in the front and rear elevation, new front wall with rail…
The lowering of existing basement floor space and the creation of a front bay lightwell with 2 windows, door and staircase to form a new …
Change the use of the basement and ground floor of 323-327 Lewisham High St, SE13 from a vacant public house to a 10-bed co-living / HMO …
These are borough-wide. See the 5 nearest to your address.
Check your address freePermitted 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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