Therefore, architects are now designing buildings that combine micro-apartments and large common areas, in which residents can hang out when they want to socialise.

"People sleep in their apartments, but the rest of the building is part of their house too," Frankel told BBC World.

Frankel’s company has built several micro-apartments projects in São Paulo, but none had broken the small-space record of 10 sq m. The company will not be able to construct such small living spaces in the future, since regulation no longer allows it. Regulation does allow, however, to build 11-sq m units. "I would make them smaller if I could," Frankel says.

The legal aspect is key. In most large urban centres, the law does not permit building on such a small scale.

Still, in cities such as Tokyo, known for high rents and for having one of the world’s highest population densities, you can find micro-apartments of as few as 8 sq m.

‘Cities are expelling people’

Micro-apartments have proliferated in other Latin American cities, but with larger sizes of around 20 sq m.

Overcrowding and excessive traffic are not new problems in the region, but they have worsened in many cities. These issues, combined with rising prices and the consolidation of an aspiring middle class, have paved the way for the micro-apartment phenomenon – at least as long as there is a demand.

Similar real estate projects are taking place in Buenos Aires, both in exclusive neighbourhoods and middle-class areas.

"Our products are for middle class people who don’t have access to housing and can’t afford to buy," says Pablo Brodsky, commercial director of Predial, a company that sells micro-apartments ranging from 18 to 30 sq m, which are priced from $40,000. "Cities are expelling people, which is why micro-apartments are here to stay.”

Yet Brodsky says that everything has a limit. For instance, you cannot build houses as tiny as those in São Paulo.

"I would not live in 10 square metres," he says.