Basement in Hounslow: Planning Permission Guide
What you need to know about basement extensions in Hounslow — planning requirements, costs, and professional guidance.
Based on 33 decided applications in Hounslow over 12 months (27 granted, 6 refused).
Hounslow has conservation areas around Chiswick (including the Bedford Park fringe shared with Ealing), Brentford, Isleworth, and Syon. Listed buildings are concentrated around Syon House, Osterley Park, Chiswick House, and Boston Manor. Article 4 Directions cover parts of Chiswick and Brentford. Flood zones apply along the Thames, particularly around Brentford and Isleworth. Heathrow noise contours affect some planning considerations in the west.
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5 nearest comparables & refusal reasons for your address.
Get my report — £9See a sample →Recent basement decisions in Hounslow
The 5 most recent decided applications. Addresses redacted to postcode area.
Installation and excavation of new external electrical supply cables to upgrade the building's electrical infrastructure.
Details of waste and recycling storage submitted pursuant to condition 18 of planning permission P/2025/1018 dated 20/11/2025 for demoli…
Alterations to and change of use of Chiswick Tower to provide 394 rooms shared living accommodation Sui Generis and 486 sqm co-working sp…
Enlargement of the existing basement, including the installation of a front lightwell and a rear lightwell with an external access stairc…
Demolition of existing building and erection of a four-storey building with commercial space on the ground and basement, with seven flats…
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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