Having a roof terrace or balcony can add an average of 12% to the value of a flat according to research by estate agents Marsh & Parsons.

The research also found that this value increase rises to 25% in coveted Chelsea and access to a communal garden commands an 11% premium.

Marsh & Parsons CEO Peter Rollings said: “Vendors have long been aware of how much value traditional home improvements such as a new kitchen or bathroom can add to a property and this research may just persuade them to covert flat roofs or balconies into habitable outdoor oases.”

Currently Marsh & Parsons estimates that just under a third of flats that come on to the market have a balcony, roof terrace or communal garden.