Rehabilitation of the old boiler room in Leverkusen

Built in 1948 as a heating plant for the former railway repair workshops, the boiler room is being rehabilitated and enlarged with a logic of reuse and construction sobriety: maintaining the existing structure and materials limits CO2 emissions compared to a new construction, while also requalifying a marker of the site.
This intervention is part of the transformation of the vast industrial complex into a mixed-use district, "Neue Bahnstadt Opladen" (housing, shops, education, and other activities), which began in 2008 on the site of the former workshops (70 hectares, employing up to 5,000 people at its peak). The project thus delivers an architectural and technical response where contemporary façade, functional value, and the site's history mutually reinforce each other.

© EHRET In the foreground, the four-story extension (approximately 1,000 m²), authorized by the heritage authorities in place of an old building that pre-existed on this site in the 1960s.

 

Heritage constraints and architectural response

Rebuilt in 1948 on the ruins of its predecessor, this boiler room (21 m high) reflects a functional and minimalist post-war architecture, identifiable by its vertical bands of narrow windows.
Listed as historical monuments – the building and two moving grate boilers – the existing elements necessitated economical and respectful reuse, posing a major design challenge. The solution combines a six-story interior structure inserted within the preserved brick envelope, and a four-story extension (approximately 1,000 m²), authorized by the heritage authorities on the grounds that a building predated the site in the 1960s.
Winner of the redevelopment competition in 2012, architect Bernd Oxen led a decade of studies and construction, culminating in the complex's completion in 2024. The mixed-use program includes offices and shops on the ground floor, while the upper levels house 32 short-term apartments (1,174 m² of usable space) for a serviced apartment operator, the site's main tenant. The project illustrates how demanding heritage constraints can stimulate architectural innovation and a program perfectly suited to the site and its uses.

 

Corten steel and expanded metal: a dialogue between memory and contemporaneity

« The railway's history continues to shape the Opladen district of Leverkusen. In addition to the boiler room, the water tower and the former main workshop building are also listed as historical monuments. They make the industrial past visible and give the new district its identity. " explains Bernd Oxen.

« The boiler room once supplied heat to the metal structures. With the Corten steel facade of the extension, we are engaging with this history while also bringing it into the present. We also wanted to create a deliberate contrast with the brick of the original building. »

The choice of materials was finalized in close consultation with heritage authorities. For Bernd Oxen, Corten steel visually evokes decay, and “ It is precisely this rusty patina that provides lasting protection to the facade and embodies conservation »

In addition to the Corten steel cladding, EHRET folding sliding shutters in expanded metal structure the building envelope. These mobile elements give the façade a variable appearance depending on its use and the time of day. Other solutions were considered, but the folding sliding shutters were chosen. because they best reflect this dynamic ».

Initially planned in Corten steel, they were ultimately made of aluminum: as the façade opted for a closed Corten steel cladding, aluminum offered lightness, ease of handling, and flexibility in installation. Expanded metal lends itself easily to aluminum, without constraints on mesh or pattern. After validation of the technical specifications, samples were presented to the client for final approval.

© EHRET Corten steel visually evokes decay. This rusty patina provides lasting protection to the facade and embodies preservation.

 

Custom-configured shutters from the EHRET standard catalog

The folding sliding shutters open at 90° to the facade and fit snugly against the building envelope when closed.

« Thanks to our standard range, we were able to configure 228 leaves with Matrico expanded metal infill, the SL 12 profile system and the necessary accessories, all from the EHRET catalog. " says Klaus Wipfler, commercial director for Germany.

The range of available references also allowed for a precise color match with Corten steel. The powder coating with a "rust – brown patina" effect recreates the appearance of aged metal, virtually indistinguishable from real oxidation.
Only the ground floor grating, sized for accessibility, required a specific drainage detail: the large elements are connected to the network, while the smaller ones flow away by direct infiltration.

« This project perfectly illustrates the harmony between function, design, and material concept. The folding sliding shutters not only provide sun protection but also become a striking architectural element in themselves. " concludes Klaus Wipfler.

 

Through this project, EHRET demonstrates its ability to combine heritage preservation, industrial precision, and architectural expression. By utilizing solutions from its standard catalog (SL 12 profiles, accessories, Matrico expanded metal infill) and appropriate finishes (Corten patina powder coating), the brand delivers a coherent, high-performance, and durable facade, perfectly integrated with the historic building and the contemporary extension.
Thus, the folding sliding shutter transcends its function of sun protection: it becomes a design element, contributing to user comfort and a distinctive architectural aesthetic. EHRET thereby confirms its role as a leading partner for the
projects where context, technique and design must respond to each other with the same high standards.