A facelift for Vienna City Hall

The entire facade of the Vienna City Hall is to be renovated during the next years. The complex project consisting of 11 stages will cost about EUR 35.7 million.

The Vienna City hall was built from 1872 to 1883. It is counted among the most significant architectural gems of the monumental Ringstraße boulevard, which became the eponymous prototype for the "Viennese style" of Historicism. Compared to the other major Ringstraße buildings, the City Hall was built from great amounts of natural stone. Having been exposed to the weather for 130 years, the stone facade is now in dire need of cleaning, structural repairs and renovation.

Detailed analysis prior to renovation

The overall renovation concept as well as the specific restoration and conservation measures are based on a detailed technical assessment carried out in cooperation with experts from the Federal Office for the Protection of Monuments, the Vienna University of Technology, specialised businesses and experienced restorers. To get a full picture of the damage and the necessary repairs, a number of test surfaces have been analysed and, in part, already renovated in small pilot projects. The aim of the pilot phase was to select the most suitable restoration techniques for the natural stone facade while avoiding the use of chemical substances wherever possible.

With its facade of more than 40,000 m³ of quarry stones and ashlars, featuring various architectural elements and imposing statues, the Vienna City Hall is an imposing witness to the role of natural stone in building construction. The different types of stone used for the building originally came from various parts of the former Austrian Empire, as well as from Italy, France and Germany. As a result of constant exposure to chemical and physical factors, some of the stones show intensive signs of weathering.

Facade subdivided into 11 project sections

The thorough preparatory analyses were completed in September 2011 as scheduled. On this basis, the City of Vienna Building and Facility Management Department has developed a detailed and cost-effective overall renovation concept. An additional package of measures ensures that everyday work at the Vienna City Hall will continue without major disruptions. The total project costs are calculated to be EUR 35.7 million.

Due to the scale of the project, the City Hall facade has been subdivided into 11 sections with a surface of about 3,200 m² each The first section is the part of the building facing Friedrich-Schmidt-Platz, where renovation is to start in September 2012. According to the project schedule, the individual phases will start in autumn and are due for completion before the winter of the following year. Altogether, the restoration project should be completed by autumn 2014.

The individual project phases

• Sections 1 und 2: western facade (facing Friedrich-Schmidt-Platz)
• Sections 3 and 4: facade of the arcade courtyard, facade facing Felderstraße
• Sections 5 and 6: Felderstraße facade and main steeple
• Sections 7 and 8: secondary steeples
• Sections 9 and 10: Rathausplatz
• Section 11: open staircase on Rathausplatz

The overall renovation concept also includes additional cleaning and renovation of the natural stone facade, pillars, gateways, gates, doors, window grilles and lead glazing, as well as a modernisation of the lighting system using energy efficient lamps.

Top quality standards

Thanks to a programme developed in cooperation with the Federal Office for the Protection of Monuments, the renovation project will meet all technical requirements while at the same time taking into account the characteristics of the different stone varieties, as well as reflecting the historical and architectural importance of the building. The conservation and restoration of natural stone is of particular importance in this context, given that reconstructing the building's material integrity – the key design element of the Neo-Gothic facade - is both the project's central task and main challenge. From an ecological point of view, special care was taken to avoid the use of chemical substances for restoration and conservation wherever possible. Hydrophobic treatment will only be applied to the main facade, while the use of protective varnishes and finishes is restricted to individual facade elements that are particularly exposed to the weather and temperature differences.

The concept for replacing and restoring missing or eroded facade parts has also been finalised in cooperation with the Federal Office for the Protection of Monuments. In line with the building's original history, all significant reconstructions will be done in natural stone rather than with customary stone repair mortar. Missing sculptural elements will be reconstructed by qualified experts, and the unique aesthetic effect of the City Hall's natural stone surfaces will be restored, thus preserving the key element of the historical architecture. Recreating the damaged facade with the original types of natural stone is also known to be a much more sustainable technology in the long term.

A task for specialists

Only certified specialists have been selected for the project, thus ensuring that the historical building substance will be treated with due care and caution. The task of renovating the natural stone facade requires both technical competence and outstanding craftsmanship.

Vienna City Hall: facts and figures

The natural stone facade of Vienna City Hall (architect: Friedrich Schmidt) has a total surface of about 40,000 m². The facade was originally built from 30,000 m³ of ashlars and 10,000 m3 of quarry stones. The City Hall is decorated with 74 sculptures by 26 different artists.