The steel and glass atrium roof will be supported by a steel ‘tree’ in the atrium. The ‘tree’ forms part of the architectural design for the new UB and will also function as a stairwell to the various floors. The roof will cover 1,200 m2 with a total glass surface of more than 1,500 m2. The curved roof will pass over the old ‘telephone tower’ of the original building, reaching more than 24 metres at its highest point. It will incorporate 383 steel bars intersecting at 1,052 points. The entire steel structure was put together on the premises of the contractor Buiting, dismantled and then transported to Amsterdam. From its hub in Amsterdam’s Oosterdokshaven, Buiting will use electric boats to move the steel to the Grimburgwal, where the roof will be welded together again at the construction site. The steel structure will be topped by an aluminium frame with glass panels.
The steel ‘tree’ in the atrium will consist of 12 pillars. It is currently surrounded by massive scaffolding. The stairs inside the pillars will be made of steel and natural stone and will be connected to the floors in the buildings by three wire-cable walking bridges. Furthermore, the steel ‘tree’ will incorporate two balconies with study places. In total, the steel components of the roof and the ‘tree’ will weight around 270 tonnes.
The atrium will be the new UB’s central meeting spot. Because of the cellar construction, the atrium will have a partially sunken floor, making it suitable as an event space. The roof will expand the new UB’s usable floor area considerably.
Not just the atrium tree and the roof will be crowd-pullers, but the historical walls and the window frames that have been restored to their original colour as well. This is thanks to the recent completion of the restoration and cleaning of the façades of the former Binnengasthuis, a job that started in late 2021. All the walls have been cleaned and the joints refilled. At the behest of the City of Amsterdam’s Monuments and Archaeology Department, workers uncovered the original colour of the window frames by scraping away more recent layers of paint. Some of the window frames have already been repainted in their original green colour. In conjunction with the restored façade, they return the exterior of the building to its original state to beautiful effect.
Construction on the load-bearing pillar of the ‘tree’ started several months ago. The new atrium roof is now also well under way to being completed. The accompanying video shows what has changed in the past year through a time-lapse of the construction of the atrium tree and the roof.