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14.02.2023 - Rotterdam

SAWA: 90% wood and balconies in slender concrete

SAWA: 90% wood and balconies in slender concrete

The SAWA residential building is an innovative project fully committed to sustainability, energy neutrality, circularity, biodiversity, and inclusiveness. With a modular main structure in Cross Laminated Timber (CLT) and slender Ultra High Performance Concrete (UHPC) balconies, the innovative residential building combines the warmth and beauty of wood with the strength and durability of UHPC.

A new landmark in sustainable architecture

The SAWA building, located in the Lloydkwartier of Rotterdam, is a new landmark in sustainable architecture. With 90% of the structure made of CLT, the 50-meter-high building is a great example of how innovative building materials can be used to create beautiful, innovative, and environmentally friendly buildings.


The use of CLT in construction has been gaining popularity due to its strength, sustainability, and versatility. The material consists of sawn, glued, and layered wood planks, with each layer oriented perpendicular to the previous. By joining layers of wood at perpendicular angles, the panel gains structural rigidity in both directions. This way, the material achieves great tensile and compressive strength, making it an ideal choice for both large and smaller construction projects.


The building's commitment to sustainability and CO2 reduction has led to a modular main structure made of CLT, which is visible in many parts of the building. This choice of material not only aligns with sustainability objectives but it is also known for being lightweight. However, this lightness presented a challenge when it came to anchoring balconies to the structure using traditional concrete. As a result, the design of the balconies required a solution that could address the weight restrictions while still being compatible with the CLT structure and sustainable focus.

The need for UHPC balconies

The SAWA building's structure and ambitions resulted in UHPC balconies from Hi-Con, an innovative material that offers a lightweight, strong, and durable alternative to traditional concrete. Compared to traditional concrete, UHPC saves up to 50-60% in weight, making it an ideal material for use in combination with CLT. The decision to use UHPC balconies for the SAWA building was a game-changer, and it marked the first large-scale project where UHPC balconies were combined with a CLT structure.


Hi-Con Netherlands will produce a total of 238 balconies and a spectacular walkway between the two parts of the SAWA building, all made from UHPC. Even the balcony slabs are made from UHPC. What a novelty! Despite the use of concrete for the balconies, the overall use of steel and concrete in the building is minimized, aligning with the building's sustainability ambitions.


Read more about the environmental benefits of UHPC here:

The choice of Hi-Con for the galleries and balconies in SAWA fits well with SAWA's ambitious sustainability goals, to minimise the use of raw materials. This design choice uses 50% less concrete than conventional solutions

Robert Platje,
Associate partner of Mei architects and planners

Award-winning collaboration

The SAWA building's design team, consisting of Mei architects and planners, Pieters Bouwtechniek, and Era Contour, worked closely with Hi-Con to design the balconies. The biggest challenge was to find a way to limit the weight of the balcony slabs while still ensuring that they were supported by the wooden consoles. The use of UHPC for the balconies not only resolved this challenge, but it also created a striking aesthetic. The UHPC material was designed to resemble wood, with a relief structure and natural color that complemented the CLT structure's warm and natural appearance.


The building, now also called “the healthiest building in the Netherlands”, has already won several architectural awards, even before construction started in the first quarter of 2022.


We will soon share more details with you about the impressive CO2 reduction potential that can be achieved through the use of Hi-Con's UHPC balconies in combination with CLT structures. Stay tuned for more information!

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