New research by real estate advisor Savills and project developer and rooftop development platform Creative City Solutions shows that adding extra storeys, so called ‘Optoppen’, to post-war apartment buildings could substantially reduce Amsterdam’s housing shortage. Constructing one or more additional levels on buildings, could theoretically create nearly 7,000 new homes – equivalent to 9% of the current shortage. This is based on the finding that 699 post-war buildings in Amsterdam have a suitable flat roof for further development. With standardised construction methods and cooperation between municipalities, homeowners’ associations, banks and developers, this approach can be applied at scale.
Furthermore, Savills investigation underlines that this move wouldn’t impact the value of top-floor residents’ homes. A review of 1,062 transactions in post-war buildings (2022–2025) shows that the price per square metre does not decline when an additional storey is added; in practice, accessibility – rather than exclusivity – is what determines value.
Savills analysis shows that lenders consider vertical extension a feasible and socially desirable form of densification, provided it is technically viable and supported by the homeowners’ association (VvE). Furthermore, it is an opportunity for further upgrades as adding extra storeys often coincides with renovation works, such as the installation of lifts and improvements to energy performance.
Charlotte de Mos, Head of Data, Intelligence & Strategy at Savills Netherlands, says:
“Rooftop development is not a silver bullet for the Dutch housing shortage, but it is becoming an increasingly important part of the solution. Our research shows that widely held concerns about value depreciation simply are not supported by the data. As a result, homeowners’ associations can make better-informed decisions about adding additional storeys.’’
Thijs Müller, Co-Founder of Creative City Solutions, adds: “The post-war housing stock was built with a forward-thinking mindset. We need that same mindset today. ‘Optoppen’ offers major opportunities to add affordable and sustainable homes within existing, sought-after neighbourhoods.”
Read the full report here.