Information exchange in existing buildings differs significantly from that in new-build projects. It is therefore essential that all partners in the construction chain work according to the same methodology. The ILS Existing Buildings Working Group is developing new guidelines for information exchange in BIM. These guidelines are now being shared with the market for validation and feedback.

Designing for an existing building requires consideration of heritage values, structural possibilities and constraints, and the technical condition of the property. Because a BIM model functions not only as a design tool but also as a communication tool, it must be practical for all parties involved: consultants, surveyors, and contractors alike. The new ILS for Existing Buildings helps optimize the digital approach to projects involving existing buildings.

Lijnbaan 101–111, originally designed by Krijgsman and Van Duin Architects and completed in 1967, has been renovated several times over the years. In 1998, D&T van Manen Architects carried out a renovation in which two large Octatube curtain-wall facades were added.

Boltt asked Octatube to investigate whether the single glazing in these facades could be replaced with more sustainable alternatives. For Octatube, which is increasingly involved in this kind of sustainability challenge, this formed a relevant part of the project. Octatube subsequently contributed to the engineering. The facade of the left-hand section, designed by Mei architects and planners, was completed in the summer of 2023.

Together with project manager Bouwplot, Boltt developed an action plan to improve the sustainability of the two buildings and merge them into a single retail environment. In a series of short, focused sprints, the existing condition, the documents for the environmental permit application and the construction drawings were worked out in parallel.

Using archival drawings, Boltt incorporated the existing condition into a BIM model, which also formed the basis for the environmental permit application. This integrated model also included Nike’s requirements. The partition walls between the two buildings were removed, a new customer staircase and elevator shaft were introduced, a new storage area was added, and the entrance was moved from Lijnbaan 111 to Lijnbaan 105.

Boltt also prepared the construction drawings for contractor J.P. van Eesteren. PelserHartman first produced a point cloud of the existing condition, which Boltt then processed and integrated into the BIM model together with the suppliers’ models. Boltt also coordinated the process as a whole.

During the later design phases, we worked closely with contractor J.P. van Eesteren to refine this approach. Our technical designers developed a practical construction method that helped maintain the pace of construction, enabling the client to begin leasing on schedule while preserving Studio Gang’s design intent.

In a building of this height, a substantial amount of technical infrastructure converges on the lower floors, precisely where a sense of openness is most desirable. For that reason, we devoted particular attention to the technical design of the MEP zones. By integrating them into designated areas, we were able to preserve the spatial quality of the double-height commercial spaces.

Because of the limited space on site and the short construction period of just 18 months for a gross floor area of 12,000 m², contractor Van Wijnen required an exceptionally detailed BIM model, fully aligned with the work of consultants and suppliers. Prefabrication and direct installation from the truck were necessary to shorten the construction period and reduce construction errors. The BIM model also had to be suitable for checking the production models of the specialist partners.

Within the BIM model, the various building components, including natural stone, window frames, structural elements and steelwork, were developed separately. We organized and coordinated clash detection sessions to align the work with the consultants and contractor. In effect, the entire building was first constructed virtually, with the assembly sequence and site logistics already considered. During the production and execution phases, Boltt also checked the production models.

From the preliminary design onwards, the project was developed as part of a construction team together with contractor Heijmans Woningbouw. In addition to the design work and technical development of the scheme, Boltt played a coordinating role and facilitated the BIM process throughout. The construction team met weekly in Rotterdam, allowing decisions to be taken quickly and the process to move forward with both speed and care.

The detailing was developed in close collaboration with Heijmans Woningbouw and its subcontractors. Because these subcontractors also contributed to the process as part of the construction team, the model and detailing took shape at a relatively early stage. As a result, fewer changes were required later in the process. This led to a key question: could the prefabricated structural elements already be produced during the design phase? In other words, how could the process be organized as efficiently as possible t?

The structural engineer’s archival drawings formed the starting point for the model, while contractor BAM was involved at an early stage in producing 3D as-built surveys and point clouds. This made it possible to verify whether the level data in the point clouds corresponded with the archival drawings. Cross-sections through the point clouds also revealed the extent of the building’s tilt and whether individual components were out of plumb.

To gain a more detailed understanding of the building’s condition, we used high-resolution drone photographs of the full exterior. By comparing these with historical images and archival drawings, we were able to distinguish between original and later elements. This made it possible, for example, to determine that part of the first floor could be demolished. The historical material also helped identify elements that were not shown in the drawings, as well as details that had been replaced over time. One example is the steel windows with opening sections, which were reintroduced in the new design.

BIM was actively used as a communication tool between the contractor, architect, structural engineer and subcontractors. Using the Archicad renovation filter, we were able to clearly distinguish in the 3D model between existing elements, demolition work and new interventions. The same applied to load-bearing and non-load-bearing components, material properties, interior and exterior elements, and NL/SfB codes. The steel supplier also used the model as the basis for sizing its components.