Roof and façade greening
Administration building Am Marschiertor

Pilot project

In summer 2025, Gebäudemanagement Aachen implemented a pioneering pilot project at the Marschiertor administration building: a 500 m² roof garden with accompanying façade greening. This is the most complex greening of an existing municipal building to date - and therefore also a learning field for future projects.

Occasion and goal

The project strengthens the green-blue infrastructure of the city of Aachen and serves climate adaptation. The greening works on several levels:

• Ecological: 1,200 plants from 40 species - from perennials and grasses to shrubs and multi-stemmed trees - create food and habitat for insects, birds and small mammals. Additional biodiversity elements such as dead wood, sand lenses and duckweed expand the range of plants on offer.
• Bioclimatic: The plants provide cooling, shade and air improvement. They bind CO₂ and particulate matter and produce oxygen - particularly valuable in a location with high traffic levels.
• Rainwater management: The green roof retains rainwater, improves the water supply for plants and relieves the burden on the sewer system during heavy rainfall by delaying the release of water.

In addition, the roof garden offers a feel-good quality: City employees with nearby offices report an improvement in their working environment.

Location and significance

The administration building is located in the city center on Lagerhausstrasse, in the immediate vicinity of Aachen's main train station. The surrounding area is characterized by dense development, sealed surfaces, road traffic and railroad tracks. The greening is a visible sign of greater climate resilience and creates a new stepping stone biotope in the middle of the city.

Design of the roof garden

The roof area offers a variety of planting and living spaces:

• Façade greening: Eight different types of climbing plants will be able to grow up to 15 meters high along modular climbing supports over the next few years. Their changing flowering times will create a varied picture all year round.
• Roof edge: Perennials and shrubs up to 1.5 meters high shield the roof area from traffic. Hanging plants such as clematis or jasmine also green the railing.
• Roof center: In addition to robust sedum species, insect-friendly perennials such as sage, mint and ornamental quinces provide variety.
• Wetlands: Three duckweeds act as temporary biotopes and provide habitats for amphibians and insects.
• Trees and raised beds: Two multi-stemmed trees characterize the roof landscape, complemented by raised beds with grasses such as pampas grass and blue fescue.

Care

A comprehensive maintenance concept was developed to ensure that the greening has a long-term effect:

• In the first three years, a total of 16 maintenance cycles ensure the development and stabilization of the green roof.
• Subsequently, regular maintenance is carried out four times a year.
• An automatic irrigation system ensures that the plants are supplied with water.
• Pruning and maintenance work can be carried out via the existing maintenance balconies for the façade greening.

Technical equipment

The roof underwent extensive technical preparation in order to secure the greenery permanently:

• Retention and drainage layer: A 6 cm high retention layer stores rainwater and releases it with a time delay.
• Substrate structure: Mounded, modeled substrate with heights between 15 and 60 cm creates a variety of planting sites - from sedum to multi-stemmed trees.
• Roof waterproofing and safety: Root-proof waterproofing, lightning protection systems, fall protection and paths for maintenance and rescue were integrated.
• Climbing aids: Specially developed, modular aluminum climbing aids on the façades allow climbing plants to grow over four storeys and can be extended as required.
• Other elements: Concrete corner stones and aluminum edge elements frame the roof surface; roof domes, drains and emergency overflows were renewed.

Challenges and prospects

The implementation was an interdisciplinary task - from structural engineering to gardening and landscaping to maintenance planning. Important points are ensuring the maintenance effort and acceptance in the working environment.

The next step: in 2026, the second half of the roof is to be greened using the same concept. At the same time, it is being examined how the areas can also be made available for use by employees in the future - for example as a lounge or meeting area.

Action week of the BuGG

At the beginning of September, the roof garden was opened for a short time as part of the BuGG "Open Roof Garden Week" campaign. City employees at the Marschiertor site were able to take a look at the green roof landscape during their lunch break. The feedback was overwhelming; many would like it to be permanently accessible - whether to take a deep breath, meet people or enjoy a short break.

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