Another characteristic element of the architecture is the approximately 1,500 square meter flat roof of the classroom building, distributed across five wings and extensively greened, which creates a striking contrast to the existing gabled roof of the administrative building with its unusual geometry. The area is completed by the approximately 900 square meter roof of the break hall, designed asymmetrically without ballast, and the approximately 100 square meter roof of the adjacent technical building.

All surfaces were constructed by the roofers above the concrete deck with a vapor barrier and EPS insulation. When choosing a suitable material for the underlying waterproofing, the tight project schedule played a significant role: “The project absolutely had to be completed by the start of the 2019/2020 school year,” recalls Ernst-Christian Gerbes. “Thus, the construction time was limited to sixteen months from the start.” This tight schedule also posed particular challenges for the roof waterproofing, which had to be completed during the winter months: “Already before the tendering process, we had suggested to casa Baubetreuung GmbH, as the executing general contractor, to use the RESITRIX® SK W Full Bond membrane, which can also be applied in cold temperatures,” adds project manager Olaf Twietmeyer. “We had used the material many times before and had always had very good experiences with it.”

The extremely durable, root-resistant EPDM membrane from CARLISLE® can be used for all types of green roofs and can still be safely and easily processed even in cold temperatures. "In the greened areas, we could have even skipped the bonding due to the sufficient ballast," says Olaf Twietmeyer. "However, since the greening was carried out a few weeks later, we still decided to bond the areas to avoid the need for temporary securing."

Before the extensive roof sealing work could begin, an intensive one-day training session was scheduled, during which all 35 employees of Gerbes Dächer were introduced to the application of RESITRIX®: "We had a similar training a few years ago when we first worked with the material," recalls project manager Olaf Twietmeyer. "However, due to regular new hires of apprentices and new colleagues, we decided to conduct another training to bring the entire team to a unified level of knowledge."

Unlike usual, this was not a first-time training session but rather an advanced training: "As a result, we were able to start at a very high level," reports CARLISLE® application technician Dierk Kubutat. "Important topics included, for example, the formation of uniform corners, uniform welding seams, and the implementation of uniform penetrations." A major advantage: "Unlike what is usually common in the industry, we didn't need to travel to the CARLISLE® ACADEMY center in Hamburg or to the CARLISLE® factory in Waltershausen, Thuringia for the training, but were trained directly at our company," reports Olaf Twietmeyer. The effort paid off on the construction site: "Thanks to the intensive training and the ease of processing the material, we were able to complete all the work without any problems. And on time and with our usual high quality!"