Mega-basements in prime London have sparked frequent debate in recent years, as homeowners look to maximise living space in properties with limited potential for outward expansion by building below ground.
However, research by Jefferies London* shows that despite the considerable time and disruption involved in constructing such extensions—often testing neighbourly goodwill—they can significantly enhance a property’s value.
Across the capital, the average asking price for a home with a basement stands at £1.2 million, which is 97% higher than the typical London property.
This premium is even more pronounced in Westminster, where basement-equipped homes command an average price of £2.762 million—122% above the borough’s overall average of £1.247 million.
In Kensington and Chelsea, the premium stands at 100%, while in Camden it is 98%.
Yet for those with the financial means, the greater challenge is locating such a property. Their limited availability undoubtedly contributes to the elevated premiums.
Hammersmith and Fulham boasts the highest concentration of prime properties with basements, but even here, they make up just 5% of homes currently on the market.
In Kensington and Chelsea, as well as Camden, basement properties account for only 3% of listings, while in the City of London, they represent just 1%.
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 that is otherwise limited in this respect.
These often multi-storey additions are utilised for a range of luxury purposes from swimming pools to cinemas and even wine cellars and it’s clear that they add serious value, whether it’s a property that has already been converted, or simply one offering the ability to do so.
However, the real issue isn’t the premium such properties command but their availability in the current market, with such homes making up around five percent or less of current prime property listings depending on where you’re looking to buy.”
