London developers are snapping up empty air above rooftops

LONDON – Look up. Some of the most interesting new developments in London are being built in the airspace above existing structures.

There are listings now popping up across sites like Rightmove for £320,000 (S$558,890) for empty airspace in the residential neighbourhood of Muswell Hill, or £150,000 in Deptford.

Airspace purchases in London largely involve buying the space above a property to create new residential units, like building penthouses above already existing blocks. Industry experts Apex Airspace estimate that this type of construction has the potential for 180,000 new homes in London, and comes at a time when homebuilding has been collapsing across the British capital. 

However, airspace projects can often run into local opposition during the process, with residents saying they cause disruption and complaints about how the extra floors atop buildings change the look and feel of a neighborhood.

In cities like New York, buying up airspace to increase a building’s square footage or to create new buildings entirely has been going on for a long time.

Take 111 West 57th Street, which was completed in 2021, for example. The super-tall pencil tower rises 435m above a 16-storey building from the 1920s. The new apartments are connected to the old building with the same lobby, though high floor apartments have their own elevator banks. A so-called “quadplex” penthouse in that building was put on the market for US$110 million (S$138.8 million) in 2025.

Buying up airspace has not taken off in London for a multitude of reasons. Many old buildings cannot take the extra load from new floors, and it is common for blocks to have multiple owners, which makes agreement on new construction difficult.

There are also complex planning constraints to protect skyline views and so-called conservation areas that make development tricky. But things became easier during the last government, which caused a flurry of airspace rights to hit the market.

In 2020, then housing minister Robert Jenrick introduced reforms that relaxed rules to add airspace builds above existing buildings.

Owners can now construct additional residential stories to either expand their own dwelling or to create new units altogether without going through full planning permissions, which are often a long and costly process. This was part of a broader set of reforms to boost housing supply, and the current Labour government has not shelved these changes. 

The new rules make it easier for developers to create new apartments in desirable areas with less red tape. The airspace is now largely being sold or leased to outside owners – and in many cases the people who live below the new flats have little say in the process. 

London has very old housing stock, the oldest in Europe, with around 60 per cent being built before World War II, according to the Greater London Authority. Much of the housing stock is Victorian, Edwardian and even Georgian houses, which in many cases have been converted from homes into individual flats.

There is little appetite or indeed permission from local councils to tear down 200-year-old buildings to build brand new ones. So utilising airspace can help find pockets to develop that don’t involve demolishing anything.

United Kingdom Sotheby’s International Realty executive partner Becky Fatemi says what was once dismissed as inaccessible air is now being seen as one of London’s most valuable untapped resources. “As London continues to grow within its existing footprint, building in the air isn’t just an architectural trend, it’s becoming a vital part of how our city sustains its future,” says Ms Fatemi.

Architects and developers who work on these projects tote the economic benefits, saying that crucially, building up is cheaper than digging down in London’s famously tricky clay terrain. 

“It’s about half as expensive to do as a basement,” says architect Robert Douge, director of boutique architecture firm Arya Douge, who has been advising on these type of airspace projects in prime central London.

The economics also make sense, he says. “If it costs say, £800 a square foot to build these in central London, and you can sell it for over £1,000 a square foot, it’s just a no brainer to do.”

Mr Douge says that the space on top of buildings is also much more attractive than dark basements.

The biggest challenge is local objections. “On the national level, the government’s been trying to make it easier to extend without planning permission,” says Mr Douge. “At local levels, there’s always been some resistance to that.”

In Camden’s Primrose Hill neighborhood, there is a plan to construct eight new penthouse apartments above a 1970s housing block called Darwin Court. There were around 100 local objections, including one from Labour councillor Patricia Callaghan, who says her concerns were focused on the disruption that locals would experience during construction and the possibility that the new apartments would change the character of the neighbourhood. 

Local resident Ben Olins has been living in the building since 1999, and says beyond the obvious disturbance aspect – no one enjoys their neighbours doing construction – he was worried about the uncertainty of the build. Like many residents who live in London apartments, he owns the leasehold, but not the freehold of the property outright.

“We as leaseholders have no control over this, no guarantee that the project would be done when the developers said, and no guarantee that it’d match the plans we were shown,” he says. He’s also concerned about service charges – annual charges paid to maintain the building – rising as a result of the new airspace builds.

No committed decision has yet been made by Camden Council on the future of the airspace builds on Darwin Court, and as a result, construction has not yet begun. Representatives for the London borough have declined to comment. 

Across town, in the upscale neighborhood of Chelsea, developer Echlin is now in the middle of creating four new luxury apartments atop a red brick apartment building on Sloane Court East. The apartments are connected, with elevators inside the lobby that will take residences up to the new penthouses. 

“What we have here is a relatively low-build building and there’s a real opportunity to add new floors,” says Mr Sam McNally, co-founder of Echlin. The building is particularly suitable for airspace development since it is a more modern structure with a flat roof instead of a classical period townhouse that tends to dominate prime central London areas. 

Sloane Court East is Echlin’s second airspace project after adding eight new apartments atop a modernist 1980s block in the Camden neighborhood in 2024. Two-bed apartments sold for £1.2 million pounds according to the Land Registry, more than the average for the neighborhood and much higher than the older apartments below.  

“There’s not big pockets left of central London to develop,” Mr McNally adds, saying that airspace is just the latest iteration of how London is changing as a city.  

Mr Will Vaughan, director of estate agency House Collective agrees. “One of the most striking shifts in London right now is the number of new homes being built on top of existing buildings. Planning changes have made this far easier, opening up opportunities to create new housing without using up scarce land.”

Still, he warns that for some buyers, these type of new homes might not be as desirable due to the contrast to the rest of the homes in a building, which are likely much older. 

“Not everyone wants to buy a shiny new penthouse sitting above housing stock that is very different, no matter how beautifully finished it is,” says Mr Vaughan. “Location, context and perception matter just as much as design.”

London will not turn into New York anytime soon, but if Londoners look up, they will likely be seeing a lot more cranes hovering above older apartments.

Air rights in New York City differ significantly, and come down to zoning rules and unused development potential. In New York, lots can transfer air rights to neighboring buildings in financial transactions.

For example, 270 Park Avenue for JPMorgan Chase expanded upwards via acquiring the air rights from neighbors like St Bartholomew’s Episcopal Church and Grand Central Terminal. This trading concept doesn’t exist in the same way in London, which is by and large not a vertical city the way New York is.

In Britain, if someone owns a freehold, they own the the building and the land it sits on, whereas a leaseholder has the right to live in or use a property for a fixed number of years and does not own the property in its entirety. BLOOMBERG