Sustainable foundations shape Amsterdam landmark

Challenges of urban regeneration

The realisation of The Frame Building, a flagship high rise residential complex in Amsterdam’s redeveloped (South East) district, faced challenges typical of urban regeneration.

Visually, it sought to create a harmonious new aesthetic for the ArenApoort urban living development, while respecting the adjacent listed building, the iconic 'Zandkasteel'. Structurally, it aimed to combine new and existing construction within the constrained site, shared with a viaduct, and built upwards to provide 213 high quality homes.

Our ground insights and progressive collaboration with Van der Vorm Engineering on foundation design, partly reusing existing piles, were key in resolving the complex dynamics of architecture and engineering. The sustainable solution delivered valuable carbon savings and at least a 25% reduction in foundations cost on the existing car park.  

Unlocking value from existing foundations

The partial or complete reuse of foundations is an increasingly viable option for the 21st century regeneration or redevelopment project.

With the advent of prefabricated concrete piles in the 1970s, records on built foundations have been better preserved, including essential data such as the quality, depth and thickness of piles. This has greatly improved the evaluation of their suitability for reuse, along with advanced Geo-data on soils, rock and ground conditions.

And increasingly, in the drive for net zero and sustainable construction, we advise clients to investigate the reuse of existing foundations, given the possible savings in time, money and reduced CO2 emissions.

Gaining insight into foundations reuse

As the structural engineer for The Frame Building, Van der Vorm Engineering faced a difficult task. The plan for redevelopment involved the demolition of an existing office building to make way for new construction partly above an existing car park. While supporting a 17-storey block (55 m high) and 12-storey block (40 m high), the foundation design also needed to consider the proximity of a viaduct bordering and partially crossing the site, and an adjoining building with a shared foundation.

Since the existing car park (part of the original building on site) was located at a lower level to the proposed new building, the initial aim was to see if the foundation could be reused in its current form. 

We interrogated our knowledge database on local soil conditions and earlier given advice, together with new monitoring data, soil investigation, to carry out foundation analysis and calculations on feasibility. This showed that a large number of additional support piles would need to be installed through the existing building in order to retain the car park. 

In achieving the building design, our evaluations with Van der Vorm’s engineers showed that the ideal and more cost-effective option would be to demolish the existing building - including car park - and create a new foundation. Based on our previous joint work on complex projects, we then investigated whether and how we could integrate the existing foundation piles into the new foundation design.

Re-engineering under changed standards

Foundations from the 1960s and 1970s were calculated according to different standards to those currently in force. The Dutch code NEN 9997-1 ‘Geotechnical Design of Constructions‘ now applies did not exist when the original building was constructed, while also the pile-bearing capacity specified was reduced.

In addition, the standard NEN 8707 - which governs the assessment of existing structures during reconstruction or refurbishment, including the geotechnical evaluation of loads and the load‑bearing capacity of existing piles– has been updated. It assumes a load test has effectively occurred (the structure has stood for years), the standard permits calculations with a slightly reduced safety factor, allowing a modest increase in utilisable bearing capacity without compromising safety.

Uneven load-settlement behaviour

Combining old and new piles requires careful, detailed calculations of possible load scenarios and design solutions.

The existing foundation under The Frame Building consisted of prefab piles, while the new foundation was based on screw-combi piles with completely different properties. This made the foundation design quite complex.

Due to the combination of existing and new piles, Van der Vorm Engineering needed to account for the uneven load‑settlement behaviour of the foundation. On this basis, the foundation design was modelled to ensure that the bearing capacity calculated by our engineers met all relevant standards and safety criteria under all loading conditions.

A pad foundation was chosen for installation under the demolished building, being designed to function ‘independent’ of the rest of the construction. A total of 47 new screw combination piles were installed under this pad foundation while 38 prefab piles were reused.

Impact: Cost-saving and sustainable

Each pile that is retained and reused results in savings in concrete, reinforcement, transport and installation.

With calculations allowing us to assume the most favourable scenario for the condition of the existing piles, it was possible to reuse a proportion of them and avoid installing 28 new foundation piles. This delivered savings of at least 25% on new piles under the existing car park. It should be noted that this does not factor in the advantage of reusing piles in positions where the piling rig would not reach, thus saving even more on reinforcement and providing a more sustainable solution for the environment.

This was a result of using less concrete and reinforcement, and less fuel and power for transport and installing materials.

Spreading the benefits

Our robust approach has proved that the evaluation and reuse of foundation piles deliver project-changing cost, time and CO2 savings for complicated regeneration like The Frame Building.

With a growing track record in this sustainable methodology, we can point to its success in other civil engineering constructions, such as quay walls and bridges.

When renovating or replacing existing assets, there is everything to gain from engaging the right blend of expertise to see if the existing foundations can be given a new lease of life in new buildings.