RIJSWIJK, The Netherlands — Early next year when a converted cargo container on a floating foundation of plastic bottles opens on the flood-prone shores of Korail Bosti, Bangladesh’s largest slum, few of its users are likely to celebrate the 320-square-foot space as a revolution. Yet, according to Koen Olthuis, the lead architect on the project, it is part of the greatest transformation in urbanism since Elisha Otis built the safety brake that gave rise to the modern elevator, skyscrapers and ultimately urban density.

“It will change the DNA of cities,” Mr. Olthuis said of the technology at the heart of his designs in an interview in his studio, a converted supermarket in this suburb of The Hague that also serves as his business headquarters.

In an era when the needs of growing urban centers are changing rapidly and rising sea levels threaten waterside construction, Mr. Olthuis has been busy working on a solution: the floating building.

Mr. Olthuis founded Waterstudio — which he describes as the first modern architecture firm to exclusively build floating houses — in 2003. More than a decade on, he and his team consider themselves pioneers in a growing movement. The firm has completed more than 200 floating homes and offices, many of them in the Netherlands, where several floating neighborhoods have sprung up in the last decade.