Delivering a project above existing infrastructure represents a colossal challenge, highlighting the central role of architects and engineers. This type of large-scale project requires extensive research on the part of professionals and builders to fully understand all site constraints, as well as significant experience and exceptional creativity. Erecting a major structure above underground infrastructure, such as a parking facility or a metro station, is akin to playing Jenga on a gigantic scale. If operations are not carried out by seasoned teams executing well-planned work, in the correct sequence and with great care, the consequences could far exceed the collapse of a small wooden tower.

The example of the future downtown Longueuil

For several years now, our teams have been collaborating with FABG Architects on the real estate development project for the future downtown Longueuil, an ambitious initiative led by real estate developer Groupe Devimco.

Ultimately, the project is expected to include an underground parking facility with approximately 400 spaces, ground-floor commercial areas, and two residential towers that will be considered the tallest buildings on the South Shore at the time of their planned opening in 2027. One of the project’s defining features, however, lies in its location directly above the Longueuil–Université de Sherbrooke metro station.

A qualified team to tackle complex challenges

Under these conditions, professional teams are faced with a wide range of complex challenges. The stability of the soil and the structural capacity of existing infrastructure must be carefully assessed. In-depth geotechnical studies are essential to anticipate the potential impacts of new structural conditions resulting from the construction. The issue of foundations is critical, as they must support the weight of the new building while remaining structurally independent from the existing underground infrastructure, a delicate balance that must be maintained at all costs. And when the capacity of existing structures and foundations cannot accommodate additional loads, creativity and ingenuity are required to ensure that no extra stresses are imposed.

Ensuring the continuity of operations for underground infrastructure also represents a major challenge. Maintaining functional access for users, ensuring their safety, and complying with codes and standards, particularly those related to fire evacuation, are all critical issues to address. The maintenance of mechanical systems such as ventilation and plumbing also requires close attention from professionals.

Finally, construction logistics present another significant challenge. Limited space makes the management of materials, equipment, and labour complex. Safety must remain an absolute priority to avoid any incidents related to the operation of underground infrastructure during construction. Given the scale and intensity of this type of work, which can generate considerable disruption, the comfort and user experience of both occupants and neighbouring communities must also be preserved and remain a daily concern throughout the construction period.

Building above existing infrastructure is a complex puzzle that highlights the critical importance of meticulous planning and close collaboration among the various project stakeholders. Engaging experienced teams capable of meeting this complex yet stimulating challenge should be a priority in order to ensure project success and the safety of all users.