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A dynamic and colourful roofscape on the nursery in Geislingen thanks to ArcelorMittal's cladding and roofing solutions
The challenge in the Geislingen Day Nursery project lies in the perception of the building, located in a valley and surrounded by multi-storey buildings. From the design standpoint, considerable attention was devoted to the image of the very extensive roof area. In close collaboration, the architect and the ArcelorMittal Arval team developed a creative and colourful solution for this dynamic roofscape.
The solution employed here is based on Arval’s K'energy system. It provides a cost-effective solution while complying with all architectural requirements and all energy-saving requirements in terms of thermal insulation.
The town of Geislingen an der Steige, as it is officially known, is located between Stuttgart and Ulm, some 15 km southwest of Göppingen. This new day nursery was built with the aim of achieving low energy consumption. It was designed by the architect Klaus Bock, who used his knowledge of local conditions to create his design, placing particular emphasis on the roof surface.
Architectural competition and winning design
The town of Geislingen organised a competition among architects for the construction of the nursery in order to increase the number of childcare facilities. Initially, the brief laid out a design for a day nursery for children three years old and older, divided into four groups, with a cost not exceeding two million Euros in total.
Subsequently, the requirements would be expanded with the construction of facilities for children up to the age of three, as well as a place for meetings with families. The site available for the project is located in Upper Filstal, a 1960s housing estate. The area is surrounded on all sides by public streets with local traffic, creating void spaces between the neighbourhood’s apartment blocks. In May 2009, the jury selected the single-storey design of the VON BOCK architectural office and awarded it the construction project. In a statement detailing the reasons for the decision, the jury praised the organisational logic and great functionality of the multi-purpose facilities as well as the lighting design. The jury also valued the fact that the building had a single storey with its characteristic split roof sheltering four bays, each with a gable roof. Constructed in a very balanced manner between the surrounding apartment blocks, this roof has a shallow slope and conforms to the length of the building’s various bays.
In his design, the architect placed special emphasis on the roof area as it is clearly visible from the surrounding buildings and from a distance, constituting an important factor in the new building’s appearance. The roof structure seeks to evoke the image of an evergreen field of flowers with elements of various colours. When it came to selecting material for the roof, the only solution was a structure based on steel sheet elements due to the requirement for the variety and intensity of colours desired.
ArcelorMittal technical advisory as an answer to special requirements
To implement this idea within the established budget, the architect consulted industry specialists at Arval from ArcelorMittal, a collaboration that lasted throughout the duration of the project.
Due to the building geometry, the required loadbearing capacity, and the requirements with regard to the structure’s fire performance, the project managers opted for a solution based on sandwich panels. Sandwich panels also ensure quick installation and excellent thermal insulation (heat transfer coefficient U <0.18 W/m²K) and weathertightness. The original intention of installing the roof surfaces with different-coloured elements resembling a mosaic was rejected for several reasons based on consultations with the specialists from Arval from ArcelorMittal, who contributed their experience in facade and roof construction. First of all, it would have been too expensive to manufacture these small elements in several colours. Second of all, from the point of view of mechanical strength, dividing the metal sheet between the ridge and the gutter would have resulted in complicated connections between sheets.
A dynamic and colourful roofscape
The alternative and more cost-effective solution was to use a standard roof structure with continuous sandwich panels onto which the coloured elements are overlaid. The sandwich panels (Ondatherm 1001 of 120 mm thickness from Arval from ArcelorMittal) were manufactured in only two different shades of green (similar to RAL 6011 and RAL 6005) thus providing some 1000 square metres as a base colour for the aforementioned 'field of flowers'. The 635 colour elements mounted on this base were manufactured in 600 x 1000 mm plates, also from ArcelorMittal, which were then individually coated.
The system employed to install these plates was originally developed under the name of 'Kalypso', originally devised to facilitate the installation of solar energy systems on roofs with sandwich panels. Using this system, the colourful elements were not attached directly to the sandwich panels, but to a specially shaped 1.5 mm sheet steel profile with an aluminium-zinc coating.
This profile, called Ondafix, was positioned where the coloured plates were to be placed and was mounted and screwed onto the longitudinal ribs joining two sandwich panels concurrently with these panels’ normal erection. Such a solution circumvented additional drilling of the outer sheet creating a stable support parallel to the roof slope for the Createc plates at the same time. This solution does not compromise water drainage or corrosion protection. The placement of the coloured elements on the green sandwich panels creates a vibrant and variegated roof.
Lighting design: special joints
Arval from ArcelorMittal also advised the architect on the detailed design of joints between panels and those created by roof openings - of great importance for the lighting design. In addition to the corresponding detailed drawings for executing the design, Arval from ArcelorMittal manufactured and supplied the side rails for the edges of the panels. This service ensured a perfect colour match between the steel side rails and the sandwich panels.
The steelmaker was also responsible for the preliminary work for the design and the planning and execution of the roof drainage system. While still in production, the thickness of the polyurethane core and of the inner lining of the sandwich panels was reduced at one end with the result that the upper plate protruded by a few centimetres, thus ensuring that the water would flow correctly into the gutter. The cut on the core was sealed with an appropriate finish and the edge of the panel’s upper plate was finished with an angular section positioned perpendicularly for aesthetic reasons.
A harmonious transition between the facade and roof
A similar design was also used for the gutter along the facade, allowing a harmonious transition between the facade and roof. For the street facade, the cladding was also supplied by Arval from ArcelorMittal. It consists of approximately 180 square metres of Pflaum linear system 300 mm-high cladding panels. The facade elements match the Createc roof plates in length and colour. The facade is angled at the eaves line concealing the gutter. Thus, the colourful roof elements, which are relatively numerous in this area, visually connect directly to the facade forming an elegant transition between the two surfaces.
Supplied by Arval from ArcelorMittal under the name of 'K’energy roof', the innovative roofing system offers advantageous energy saving (heat transmission coefficient U less than 0.15 W/m²K), as well as quick and secure mounting. From an architectural viewpoint, it should be emphasised that the system allows for numerous, simply achievable creative solutions for a roof design.
Klaus von Bock, Architekturbüro von Bock
City of Geislingen an der Steige
Architekturbüro von Bock, ArcelorMittal Construction