Isler Roof Geislingen

Reproduction of the atrium roofing of the Daniel-Straub secondary school in Geislingen an der Steige

Building description:

The listed secondary school is a four-story exposed concrete building with a central atrium.

Particular design features are the sculptural concrete parapets, the central, expansive staircase and the crystalline-looking roofing of the inner courtyard as a retractable roof made of fiberglass-reinforced polyester.


The architectural effect and the geometric dimensions of the reproduction of the atrium roof are identical to the original according to the design of the Geislingen architect Veit Gmelich while using the Isler system for large span rooflight.

The original framework dimensions of the roof surfaces, which are based on those of the coffers, are largely maintained. The coffers are visible from the inside due to their translucency. Their original arrangement is therefore part of the design.

The inner courtyard roof acts as a shell like structure out of triangular panels. All load bearing elements are made of glass fiber reinforced plastic (GRP). The roof transfers its loads to the articulated supports via the plate effect. The supports are constructed in a specific manner to allow unimpeded expansion and compression due to temperature fluctuations.

The large-format GRP sandwich panels consist of GRP coffers (height 220mm) between two a fixed GRP layers. The component panels are connected by means of hip / valley / ridge elements and a tie rod, which are bonded to one another.

Object characteristics new roofing:

Planning: Elke Genzel, Pamela Voigt

 Planning hub: Dr.-Ing. Lars Janke (in cooperation with Prof. Dr.-Ing. Alexander Stahr)

Material tests:

IMA Materialforschung und Anwendungstechnik GmbH (

TU Chemnitz, Professur Strukturleichtbau und Kunststoffverarbeitung (

Object characteristics original roofing:

Address: Daniel-Straub secondary school, Uhlandstraße 15, 73312 Geislingen

Architect: Veit Gmelich, Geislingen

Structural engineer: Heinz Isler, Burgdorf, Switzerland

Execution: Reinke KG, Michelstadt

Year of construction: 1969

Dimensions: approx. 15.6 mx 18.6 m

Floor plan area: approx. 220m²

Roof area: approx. 285m²


Material: glass fiber reinforced polyester resin, translucent

Material support: steel


Around 1995 the roof was renovated

Planning: 2012-2014
Construction: 2013-2014