In the heart of the Wisselspoor area in Utrecht, Zecc Architecten transformed a 1950s industrial warehouse into a future-proof work building. The former "Onderdelenloods," once part of the Royal Dutch Factory for Tools and Railway Equipment, now houses five spacious studios, including Zecc's own office. This adaptive reuse marks the final step of phase one in the Wisselspoor area development and is a special project in which Zecc handled both the design and the development itself.
When Zecc discovered the old NS-warehouse in 2021, it was still in use. Despite that, they saw its potential. Together with Synchroon, they explored whether the building could be used for housing or workspaces. Due to thermal and acoustic issues, housing wasn’t feasible, so they chose to redevelop it as a workplace. To independently realize the plans, Zecc founded a separate company: Zecc Vastgoed BV.
The design: preserving identity, space, and transformation
The transformation was done in collaboration with Bouwstructuur (structure), Visscher Bouw Advies (installations), and R&R Bouw (contractor). The original industrial structure was the starting point. Instead of major changes, the focus was on preservation and reuse. For example, the original slim steel frames were kept and fitted with new HR++ sunproof glass, and the steel roof structure was made a key feature of the new interior.
On both sides of the ground floor, the façade was opened up with new glass walls to highlight the repetitive design of the building. At the front, it now connects to a public park designed by DELVA Landscape Architecture, part of the overall landscape plan. At the rear, a shared outdoor space was created with fencing designed to match the warehouse style.
Inside, six studios were created, five of which are offices ranging from 225 to 350 m². The two middle units were combined into a 570 m² space used by Zecc itself. All studios were built around a new wooden mezzanine on a steel frame and are connected via a two-level void. Removing the suspended ceiling revealed the concrete roof panels and steel trusses.
All studios share a unified look, with the same LED light lines (up and downlight). The windows are functional, and on the south side equipped with sunshades. The architectural choices are subtle but carefully considered, aiming for long-term sustainability.
Smart technology and sustainability
Technology and sustainability are key parts of the transformation. Each studio works independently with its own meter, heat pump, ventilation system (WTW), and internet. This setup not only solved issues with limited power capacity in the area but also allows each tenant to manage their own unit easily.
The façade is built as an insulated cavity wall with an Rc-value of 2.5 – a big upgrade from the uninsulated original. A new insulated concrete floor was installed, and the roof was insulated from the outside. The floors have low-temperature heating and cooling, supported by extra wall-mounted convectors to prevent cold and overheating. The skylight was replaced with modular Velux units, which can open for ventilation and include sunshading.
The building was upgraded from energy label G to A++, with some units reaching A+++. When used correctly, the building is even Paris Proof and received a GPR certificate with a minimum score of 7.5 in all sustainability categories.
Parts of the demolished annex were reused in the interior. Old window frames, doors, and wall panels were repurposed in meeting rooms and planters. The central lunch bar, a daily meeting point for the team, was built from leftover materials. Panels from the annex were reused as wall finishes, adding both acoustic function and artistic character.
Character in the façade
A subtle but striking feature is the façade lettering. The word ‘ONDERDELENLOODS’ is spread over fifteen window bays and looks like it has always been there. It connects the building’s past with its new identity.
