Commerce 46: A new and particularly sustainable office complex in the center of Brussels

The current Commerce 46, a previously renovated office building, was acquired by real estate specialist Immobel SA in 2018. Initially, a reuse of the building was considered, but due to its layout and completely closed front façade, this intervention proved too complex. It was finally decided to demolish the building and build a new, sustainable office complex. In itself a logistical challenge for Algemene Bouw Maes nv, due to its location in the center of Brussels. 

The renowned architectural firm Jaspers-Eyers worked together with Office Architects and Algemene Bouw Maes nv for this project. They engaged Dutch Engineering for the calculation and delivery of the steel-plate-concrete floors.

BREEAM 'Outstanding'

This is an innovative and high quality office building of 13,800 m2 spread over 12 floors above ground. Located underground are the 70 parking spaces with charging points, the bicycle parking facilities and all the technology. The latter to preserve the roof to the maximum. Situated at the intersection of two major thoroughfares, the project fully meets the new needs for office space in the midst of a rapidly changing neighborhood.

Sustainability is ensured, among other things, by a BEO field, the installation of solar panels, the construction of green roofs and the application of water recovery. The entire complex thus saves up to 26,000 tons of CO2 emissions per year compared to a conventional building. Commerce 46 rightly achieved the highest sustainability label as a result: BREEAM 'Outstanding'.

Light-footed architecture

Loïk Eyers, partner at Jaspers-Eyers architects: "We resolutely opted for an open, transparent and inviting concept in a slender steel and concrete construction. Maximum incidence of light is guaranteed by the large glass surfaces in a curtain wall system of anodized aluminum. The steel columns were deliberately kept visible, adding to the honesty of the building. On one side, the structure harmoniously matches the listed building next door in terms of height, appearance and proportions. The facade comprises 3 volumes, each with a distinct appearance. The stepped structure, the penthouse section with awning, the central garden on the ground floor that is visible from the street, the two roof terraces of 300 m2 each and various other green spaces already create a distinctly playful and airy effect and a particularly pleasant working environment."

Tiered structure

Jonas Van Durme, project manager at Algemene Bouw Maes nv: "The building consists of a steel structure around 3 concrete cores and features slender, concrete floor slabs. In the summer of 2020, we started the demolition of the basement. These demolition works were carried out in phases with the 12 m deep shoring works and installation of the berliner walls. We also applied the BEO field with 70 borings to a depth of 90 m, followed by the crane foundations."

The basement was poured entirely on site with one-piece walls up to 9.5 m high. "The floor slabs on the parking floors in the basement were constructed under slope, which made the realization of the walls difficult. Using two tower cranes, the steel structure was raised in stages, with the steel and core being applied simultaneously. To preserve the structure's fire resistance, the steel columns were filled with concrete and protected with fire-resistant coatings. Some 700 tons of sectional steel were used for the entire structure, with the steel columns being partially incorporated into premium walls."

Challenging floor construction

The floors in such slender steel structures usually present a challenge on more than one level. Large spans have to be taken into account, in the case of Commerce 46 up to 6 m, with maximum rigidity, a limited floor thickness and complex piping and cabling, typical of a contemporary office building. It was decided to put this specialized and challenging task in the hands of Dutch Engineering.

Dutch Engineering Raadgevend Ingenieursbureau B.V., based in Zoeterwoude, has extensive know-how in the design and supply of steel sheet-concrete floor systems for numerous applications. Historically, the company has so far been primarily active in the Netherlands, but the Belgian market is also increasingly captivated by its reliable and intelligent floor systems. Besides Commerce 46, it was previously responsible for the steel sheet-concrete floors of the IMEC parking garage in Leuven and for the Havenhuis and the Royal Museum of Fine Arts in Antwerp. Henk Prins, owner of Dutch Engineering: "For Commerce 46 we were involved in the project quite early in the tendering phase, which allowed our engineers to make a valuable contribution right from the preparation stage. Commerce 46 presented the necessary challenges for us, especially in terms of the large spans, fire safety, limited floor thicknesses and complex technical piping. The latter ran parallel to the floor and in some places perpendicular to it. The floor thickness was only 17 cm, with outliers as small as 12 cm. Only at the level of the terraces could we work a little thicker. In total, we supplied over 10,000 m2 of ComFlor 51+ type profiled panels for this project, which were delivered to the distribution hub of the Brussels Havenlaan."

ComFlor 51+ is a steel sheet with traditional dovetail profile. The specific profile geometry provides an excellent mechanical sliding connection to the concrete. The profiles combine excellent stiffness with a steel sheet thickness of only 0.90 mm.

All in all, the impact of the pandemic on the progress of the works was relatively limited. Completion is scheduled for the fall of 2022, after which the only tenant, ING Belgium, will be able to occupy the new offices.