Showcases Byldis

Hourglass Amsterdam, The Netherlands

Focus on sustainability

A beautiful building in the shape of an hourglass was created in no time at the Zuidas. Hourglass will be a sustainable office building with 115 long-stay hotel apartments. The various levels are made from 585 precast sandwich elements.

Completion: October 2019 Client: Hurks Bouw

Hourglass Amsterdam, The Netherlands

Focus on sustainability

Completion:

October 2019

Client:

Hurks Bouw

1. The project: Hourglass

Hourglass, the name says it all. This beautiful building in the shape of an 80-metre-high hourglass was built in no time at the Zuidas in Amsterdam. Hourglass is a sustainable office building with 115 long-stay hotel apartments and 700 m2 of hospitality and retail spaces. The building’s architecture was inspired by the work of Romanian sculptor Constantin Brâncuși, and key to the success of the design of the façade are the unusually large natural stones set with very small joints.

Sustainability is the focus of this project. Hourglass makes as much use as possible of natural light and fresh air within the building. This makes Hourglass a healthy building with a high level of comfort (climate class A). The heating and cooling systems are entirely sustainable, and the roofs are fitted with solar cells. Upon completion the building will receive the BREEAM Excellent certificate. This was helped by Byldis using concrete with up to 50% cement replacement products to reduce the embodied CO2.

3. Why was Byldis chosen?

Byldis developed the idea of building up the wall panels offsite in their factory as an alternative to on site construction. This gives the Architect the impression of an open jointed rainscreen while achieving the very high tolerances required for the project. In addition, the manufacture of the panels greatly improved the Health and Safety situation where the heavy stones could be safely manoeuvred mechanically in a factory rather than manually on the scaffold on site. A key benefit of using Byldis precast elements is that the build time is greatly reduced. The construction of Hourglass progressed considerably quicker than would have been possible with an traditional rainscreen.

The chosen design is known as the Byldis integrated system of structure, watertightness, insulation and the architectural façade of stone and windows developed as one item.

Diederik Dam, Hourglass architect: “Doing this without using precast elements is probably not completely impossible, but very nearly impossible. This is due to the complex shape of the building, the circumstances in which it has to be constructed, the large sheet of natural stone we included in the design... this can really only be realised with precast concrete.”

4. Challenges & solutions

Natural stone outer leaf
The outer surfaces of the sandwich elements of Hourglass are finished with natural stone (Turkish Limestone, 40 mm thick) fitted to an insulated panel in the factory.

Extreme precision due to extra narrow joints
The project includes 585 panels including 193 columns, up to ten metres in length. The joint sizes across the building are consistent with the joints between the panels, as well as the natural stones being only twelve millimetres wide. This demands extreme precision in the assembly. The precast elements are put in place using two tower cranes, a working method that is only made possible due to an intensive collaboration between Hurks Bouw and Byldis.

Hourglass silhouette
The facades of the building slope slightly inwards at the bottom and slightly outwards towards the top, thus creating an hourglass silhouette. The complex shape was a challenge that has resulted in over 1000 different stone sizes in the facade. From the third storey upwards, the facades are constructed using precast elements. The principle of M-shaped elements continues from top to bottom. Despite the sloping facades, all the joints between the sheets of natural stone are horizontal.

Complex facades
The curtain walling that runs up the corners is enormously complex benefiting from Byldis’ expertise in 3D design. The curtain wallings on the ground floor and the characteristic corner curtain wallings are installed on site. Due to the sloping shape of the building, it was necessary to develop the drawings in 3D. These drawings were then used to control the CNC machine tools in order to produce the profiles in the right way. All windows were developed and produced using the 3D model. Custom-made swing-out scaffolding was developed to give safe external access where required locally without the need for general scaffolding.

Glass, abseilers and suction cups
Fitting the corner glass was the greatest challenge at Hourglass. The glass was placed on the desired floor using a glass robot and then hoisted outside using a spider crawler crane. Guiding the sheet of glass into place on the outside of the building was initially done using aerial platforms. But as the building became taller, abseilers were needed. The abseilers secured their ropes several storeys above the work area and then descended down the outside of the facade to the desired position. They remained hanging there to guide the sheet of glass into the opening and screw it into place. As the ropes were secured to the roof at that time, and the kink in the hourglass shape sloped three metres further inwards, it was necessary for the men to pull themselves towards the facade using suction cups in order to carry out their work.

5. Facts & figures

The project	Office, hotel, car park, retail and restaurants
Location	Amsterdam, The Netherlands
Scope of project	Approx. 80 meters high, 42,000 m2 floor surface area, 19 storeys
Byldis contribution	engineering 585 sandwich elements 193 columns 2 beams 780 aluminium frames with glass 7 sliding doors 20 curtain walls (BG, 1^st and 17^th floor)
Byldis expertise involved	Byldis total concept (engineering, precast concrete, aluminium facades)
Start of production Byldis	January 2017
Start of assembly Byldis	February 2019
Expected completion Byldis	April 2020
Client	Hurks Bouw
Architect	DAM en Partners