Prime London Mega-Basements Command Property Premiums as High as 122%

New research by Jefferies London, the prime London residential brokerage, has revealed that basement properties in the capital’s most desirable areas are commanding a staggering premium of up to 122% over typical market values — despite accounting for just 3% of current listings.

Once controversial due to their complex construction and impact on neighbours, prime London’s mega-basements are now a key feature of luxury homes, often housing amenities such as swimming pools, cinemas, gyms and wine cellars. As outward expansion is limited in many historic central London locations, these subterranean additions have become a sought-after method of significantly increasing internal square footage.

According to the research*, homes with basements across Greater London are currently listed at an average of £1.2 million, which is 97% higher than the average asking price of a property without a basement.

The premium is even more pronounced in Westminster, where homes with basement space are listed at £2.762 million, compared to the borough-wide average of £1.247 million — a 122% uplift.

Other boroughs with notable premiums include:

• Kensington & Chelsea: +100%
• Camden: +98%

Despite the clear demand, basement homes remain extremely rare.

• In Hammersmith & Fulham, where supply is highest, they account for just 5% of all listings.
• In Kensington & Chelsea and Camden, basement homes represent just 3% of listings.
• The City of London has the lowest availability, with just 1% of homes featuring basement space.

Damien Jefferies, Founder of Jefferies London, commented:

“Whilst their construction may have caused controversy in recent years, the mega-basement continues to be a feature that many prime homeowners are keen to implement, as it tends to be the only viable option when it comes to adding serious additional space to a home.

These often multi-level spaces are used for a range of luxury purposes, and the value they add is clear — whether already built or simply a possibility for future development.

The real challenge today isn’t the price premium, it’s the lack of availability. Properties with basements make up just a fraction of current listings in the capital’s prime markets.”

? Data Sources

*Figures based on current Zoopla listings and average asking prices for basement homes across selected London boroughs as of May 2025.
Full data tables and methodology are available upon request.

? About Jefferies London

Jefferies London is a specialist prime residential property brokerage, focused on the luxury market in central and south-west London. Leveraging a digital-first strategy and decades of combined market expertise, Jefferies London delivers precision marketing and tailored client service for both UK-based and international buyers and sellers.