London may have found a radical solution for its housing crisis—building new homes on roofs.

Britain’s capital could benefit from 41,000 new homes if it developed properties on unused rooftops, adding a potential 28 million square feet of real-estate to its two most central zones, according to research from Knight Frank, a global property consultancy firm.

The real-estate firm says there are as many as 23,000 buildings in the heart of the city that are suitable for rooftop development, which would ease the pressure on developers to find unused plots of land in London’s dense center.

The data was produced using Skyward, new geospatial mapping software, developed to investigate the feasibility of the UK government’s suggestion that “buildings can be extended upwards by using the ‘airspace’ above them” in a recent housing white paper.

Image: Quartz

In recent years, there has been growing concern that London’s famous skyline is being ruined by new developments, but rooftop developments could offer a solution.

The volume of roof space that could be used for new housing is equal to eight of Dubai’s Burj Khalifa, the current tallest building in the world at 830 meters. By spreading volume across thousands of buildings in London’s center, it avoids the need to build new, taller towers to house Londoners. (But of course, this is unlikely to stop developers building more skyscrapers to meet demand for office space.)

Housing volume isn’t just an issue that London is facing alone. Cities across the world are all grappling with the same problem: how to meet rising demand for housing and how to make homes cheaper for those living there. New Zealand is planning to ban foreigners from buying existing homes. Meanwhile, Canada has already tried imposing a steep tax on foreign buyers, with limited success.