Rapid rise of The Pulse is all thanks to prefab

Anyone who regularly drives on the A10 Zuid cannot fail to notice that a new structure is dominating the field of view. Since August 2021, VORM Bouw has been working on the construction of the multifunctional complex The Pulse of Amsterdam – the first year still reasonably out of sight, when the focus was on building the construction pit and the foundations. But since the first floors of the complex were built, it has seemed as if a new floor has been added every single week. ‘That’s not too far from the truth’, laughs project manager Joachim Raap, as we take the builders’ lift to the 24th floor of the office tower. ‘Connecting the two towers to the lower central section was a challenge, so that took longer. Once that was in place, we could head upwards and we added a new floor every eight days.’

The residential and office tower of The Pulse of Amsterdam are connected to each other by a lower part of the building made up of nine floors. This central section will soon be home to amenities, such as a cinema and hospitality facilities, with a real urban forest rising up on top of it. ‘The three sections of the building need to connect to each other, but also be able to move separately. That’s where the challenge lies’, explains Raap. ‘It may sound crazy, but concrete needs to be able to move a little or otherwise it cracks. To enable that movement, we built expansion joints between the buildings. These are then filled with reinforcements. The sections of the building are also pinned to each other by means of dowel bars. The exact calculation and execution of this kind of structure requires real precision.’

The builders’ lift is hot and sweaty, but once on top of it, we are treated to an amazing 360° view of Amsterdam. This tower reached its highest point of 95 m in early September and the roof here has already been waterproofed. ‘We were able to get this high so quickly thanks to the use of prefab elements, which are really easy to apply’, says Raap as he bends slightly over the safety rail to point out the top of one of them. These monsters measuring 3.6 x 3.6 m are made from biocomposite, partly produced using plastic bottles. There is a large window in the centre of each element. ‘You use the lifting eyes to hoist them up. They then serve as the anchor for the façade element on top of them. The façade on this tower is almost complete. I’d estimate that there are around a thousand of these elements on the building, each with two solar panels on it.’

The final floor of the residential tower differs from the floors below it and its construction is especially complex. The top layer is actually made up of two in one, explains Raap. ‘The ceilings on the lower floors are 3.3 m in height, but the ceiling on the top floor will actually reach around 7 m.’ Until now, the contractor has been able to pour the concrete ceilings in situ. This involves the builder using steel shores – posts that press between the floor and the ceiling. On top of these, sheets are used for the formwork for the next floor, which is then reinforced and the floor is poured. And so it continues. Raap: ‘That’s not possible on the top floor because it’s too high. Instead, we’re building a temporary support structure on which a prefab concrete wide-slab floor will be laid. This consists of concrete sheets that are 70 mm thick. Because we’re working at such great heights, we need to secure the scaffolding extra carefully, including with diagonal braces.’

A little later, we are on the scaffolding on the residential tower, which is covered with pieces of brown and red strips. ‘Look, you can see bricks, can’t you?’ smiles Raap. Rather astonished, we take a look at the brown and red strips – no thicker than the sole of a shoe – on the façade, which appear to consist of bricks laid on top of each other. Raap: ‘To the eye, these mineral strips are indistinguishable from real bricks, but producing them consumes three times less energy than it would for a classic façade.’ Raap takes us to a section where we can clearly see the different layers of the façade. ‘Look: a wood-frame element, then a layer of rock wool, followed by a layer of reinforced plaster – and then the glue for the mineral strips. The glue is grout-coloured, so when the strips have been affixed, the job’s done. But don’t be mistaken – the façade is in the style of the Amsterdam School of Architecture, with lots of edges and corners. Applying those strips is precision work.’