Zalmhaven, Rotterdam | World's highest residential tower to be prefabricated

The 215 meter high tower Zalmhaven I will be constructed entirely of prefab elements. Based on the aesthetic design by architect Van Dam & Partners, the structural design by BAM Advies & Engineering and commissioned by BAM Bouw en Techniek - Grote Projecten, Brabant-based Byldis Prefab is supplying and assembling a rich variety of prefab elements. From interior walls in 300, 400 and 500 millimeter thicknesses to facade elements and elevator walls of 300 and 400 millimeters and balconies and wide slab shells of 100 millimeters. A total of 770 complete façade elements, 1,140 interior walls, 400 balcony slabs and 250 staircases and landings are being installed from the 5th to 54th floors at a rate of 1 floor per week.

Our environment is rapidly urbanizing. Especially in the Randstad, where the demand for housing has never been greater. In the congested area between Amsterdam, Rotterdam, The Hague and Utrecht, hundreds of thousands of new homes must be built by 2030 to meet the growing demand. The only solution to this, is to go up in height. "However, inner-city high-rise construction is not an easy job," knows Jacco van Dijk, CEO at Byldis. "Developers, contractors and other stakeholders are faced not only with crowded city centers, limited spaces, noise restrictions and time-consuming traffic and safety measures, but also with limited budgets and a shortage of craftsmanship. Byldis - until recently known as Hurks building components and engineering - offers a solution to this."

50% construction time savings

Byldis' ambition, as the market leader in integral assembly solutions within the European high-rise segment, is to permanently change the construction world. "We do this with more than 50 years of experience in engineering, precast concrete and facade technology," said Van Dijk. "Together with over 400 skilled colleagues, we work extremely hard on innovative building concepts every day. From inquiry and design to prefabrication and assembly in one of our plants, followed by assembly at the construction site. With our innovative prefabricated building concepts, we deliver projects within half the normal construction time, made to measure and of a very high quality. In addition, safety on and around the construction site is significantly increased. Only a few personnel are required to assemble the elements. Fewer transport and lifting movements are required and noise pollution for the surroundings is reduced to a minimum. In the construction of Zalmhaven I, these advantages come into their own perfectly."

Assembly from a lifting shed

Originally, Zalmhaven I was to be built traditionally, Van Dijk explains, with walls, floors, columns and beams poured in-situ. "Because of the busy inner-city location, tight construction site and short lead time, however, prefabricated concrete elements were chosen. In a construction team with the chief structural engineer, architect and contractor, we turned the building design into a precast system, focusing not only on the engineering and structural calculations, but also on the feasibility of the project. All precast concrete sections are broken down into manageable, repetitive elements, which can be easily transported, hoisted and assembled." A self-climbing lifting shed with 2 pieces of 40-ton overhead cranes is used for assembly. This methodology was previously used successfully at Erasmus MC, which also involved BAM Bouw en Techniek - Grote Projecten and Byldis. "Our trucks deliver all the facade elements, columns, wide slabs, internal walls and stairs just-in-time under the crane, after which the overhead crane lifts them up directly from the truck. On the floor, the elements are placed on a yoke, after which an assembly crane picks them up and puts them in the right place. After pouring the wide slab floors, the building shed can be raised one floor, after which the hoisting and assembly cycle is repeated. This makes it possible to work very quickly and in a sheltered way. In fact, the skyscraper is built entirely indoors."

Challenging corner elements

All exterior façade elements are constructed from a load-bearing interior wall, an insulation layer and a façade finish of natural stone, and are delivered on site including profiles, doors and glass. "One challenge is the structural corners of the building, for which we have developed a special, three-dimensional corner template," says Van Dijk. "Zalmhaven I will be - as far as is known - the tallest residential tower in the world to be built in a 'dry' precast concrete system. That brings with it specific challenges. Because the higher a building, the greater the instability and wind load. In order to absorb these forces properly, the correct execution and coupling of the load-bearing elements is indispensable. The corner elements play a key role here. The concrete for these elements is poured vertically in a single pour in a floor-high mold, resulting in very dimensionally stable corners."

Because storage is impossible for a 215-meter-high residential tower, all concrete elements are produced assembly-by-assembly. Meanwhile, production of the first elements has started. In week 6-2020, assembly will start, after which 50 weeks later the work will be completed.

While Byldis Prefab provides all the concrete elements for Zalmhaven I, specialist in aluminum facade systems Byldis Facades is responsible for the production, supply and assembly of the aluminum facades of the two low-rise towers and connecting plinth.