Projects / 1/31/2025

New stone floors to recreate the atmosphere of a seventeenth century high school

Mapei products were used to treat the substrates and install stone in the reading room of a state library which was lately renovated

The State Library in Passau, Germany, underwent a major renovation project (2014-2018) to modernize its historic reading room, originally part of a 17th-century Jesuit high school. The project replaced a glass dome with an innovative steel and glass roof structure and new locally-sourced limestone flooring was installed. The renovation, which emphasized sustainability, made use of a complete system by Mapei for the installation of stone.

The State library in Passau, which is managed by the Federal State of Bavaria, is dedicated to books covering many different disciplines, particularly humanistic studies. The heart of the building is the reading room situated in what used to be the internal courtyard of a Jesuit high school built in 1639. The glass and metal roof of the courtyard, built in 1970, was replaced in 2018 because of the damage it had suffered.

Between 2014 and 2018 the Schmied architecture firm and the Haushofer engineering studio, together with the local heritage authority, worked on a project to renovate these spaces: as an alternative to the previous dome, it was decided to install a steel and glass roof for the courtyard made up of interweaving sections. On the outside the structure of the roof blends in with the profile of the roofs of the buildings nearby, while on the inside it blends in with the profile of the arches, allowing natural sunlight to enter the space and create a bright, spacious and quiet atmosphere. The original look of the courtyard has been preserved thanks also to new stone paving to replace the old textile flooring.

Locally-sourced limestone for the floors

The first phase of the work on the new floors was a site survey by the contractor commissioned to carry out the job, Karl Bachl GmbH & Co. KG and experts from the Technical Services team of Mapei GmbH, a German subsidiary of Mapei Group. During the survey the condition of the substrates was analysed in order to propose a specific installation system suitable for the type of material chosen: limestone from the Bavarian town of Kelheimer. This type of stone is un-layered coral reef limestone with fragments of coral and fossil and fine lime sediments which solidified over time to form a particularly compact and strong type of rock. This type of stone was installed on 250 m² of floors in the Passau Library, made up of 2 cm slabs with a polished surface and a light-coloured finish with a reddish hue in certain areas.

Limestone from the Bavarian town of Kelheimer was installed on the new floor with MAPESTONE 1 (an adhesive distributed in Germany by Mapei GmbH).

Perfect preparation of the substrates

The substrates were made up of asphalt screeds which the Works Director wanted to maintain.

To make them suitable to receive the stone covering they were treated with ECO PRIM GRIP ready-to-use, multipurpose primer (now available on the international market with the name ECO PRIM GRIP PLUS). This product, which has very low emission of volatile organic compounds (VOC), improves the adhesion of levelling compounds and adhesives on non-absorbent surfaces.

The substrates were then levelled off with PLANITEX D10, a self-levelling product produced and distributed on the German market by Mapei GmbH. The next step was to apply PRIMER G, a synthetic resin-based primer in water dispersion, again with very low emission of VOC, to improve adhesion of the stone slabs installed using MAPESTONE 1 adhesive, which is manufactured and distributed on the German market by Mapei GmbH.

The joints were grouted with ULTRACOLOR PLUS, a quick-setting and drying, polymer-modified, anti-efflorescence and mould-resistant mortar free from Portland cement, again with very low emission of VOC.

ULTRACOLOR PLUS mortar was used to grout the joints.

A highly sustainable system

The client and design team decided to privilege the use of sustainable products. And this is why Mapei GmbH proposed materials with very low VOC emissions, for both preparation of the substrates and installation of the stone floors.

What is more, CO₂ emissions from ULTRACOLOR PLUS, the mortar chosen to grout the joints, are measured along its life cycle in 2025 using LCA methodology, verified and certified by means of an EPD (Environmental Product Declaration), and offset through the acquisition of certified carbon credits in support of forestry protection projects*.

Limestone from the Bavarian town of Kelheimer was installed on the new floor with MAPESTONE 1 (an adhesive distributed in Germany by Mapei GmbH).

Project information

City library, Passau (Germany)

Owner: Bavarian State Ministry for Education and Culture, Science and Art

Design: Thomas Schmied and Markt Schwaben, Haushofer Ingenieure

Flooring contractor: Karl Bachl GmbH & Co. KG

Period of renovation: 2014-2018

Period of the Mapei intervention: September 2017

Intervention by Mapei: supplying products and technical assistance for installing stone floors

Mapei coordinator: André Wallner, Mapei GmbH (Germany)

*CO₂emissions measured throughout the life cycle of products from the Zero line in 2025 using Life Cycle Assessment (LCA) methodology, verified and certified with EPDs, have been offset through the acquisition of certified carbon credits in support of forestry protection projects. A commitment to the planet, to people and to biodiversity.