Rooftop housing could ease Dutch shortage with 100,000 homes, but few built: Study
Building additional housing by adding new floors to existing apartment blocks, a method known as optoppen, could provide 100,000 homes by 2030, according to new research from ABN AMRO. But the study shows progress is falling far short, with only a fraction of that potential being realized.
Two-thirds of those possible units, about 67,000, could be built on complexes owned by housing corporations. Yet only 7.2 percent of that potential has been achieved so far, the study found, citing data from the consultancy Stec Groep.
The bank points to restrictive parking requirements, slow municipal permit procedures, and hesitance from housing corporations as obstacles.
“Cities continue to enforce parking standards,” Claire van Staaij, real estate sector banker at ABN AMRO, told NOS. “If the rule is one and a half parking spaces per household, and you add households by adding extra floors, then extra spaces must be created. But in city centers, space is already scarce.”
Adding new layers on top of existing buildings can be quicker than traditional construction, has less environmental impact, and offers opportunities for sustainability upgrades. Many of the potential projects involve postwar apartment blocks with flat roofs built with strong, overcapacity structures, which make them technically suitable for additional floors.
Still, support from residents and owners remains limited. To add new levels to privately owned apartments or free rental housing, at least 80 percent of owners in a homeowners’ association (VVE) or tenants must approve.
Developers argue the method has strong potential. “You really benefit from this way of building,” Bram Hertzberger of Creative City Solutions told NOS. Prefabricated units can be installed on rooftops within months, though adjustments such as extending stairwells or ventilation remain complicated.
Still, municipal parking requirements continue to block projects. “If you put 44 apartments on top, you need to provide an average of 66 extra parking spaces,” Van Staaij the newspaper. “With existing buildings, that is often impossible.”
Resident resistance also plays a key role. Many tenants and owners are unwilling to support construction above their homes. ABN AMRO frequently hears objections such as “I don’t want people living above me” or “I won’t do that to my tenants.”
Steven Wayenberg of Vereniging Eigen Huis called adding new floors “an interesting opportunity” but warned it is no small undertaking. “Combine it with sustainability, and you kill two birds with one stone: the building is upgraded and future-proof,” he told NOS. “But this is a major project. You cannot arrange it with a few volunteers. Professional parties are needed, and the financial risk should not fall solely on residents, or support disappears quickly.”
