Bregenz Opera House
This polymeric roofing membrane has stood the test of time
As part of a recent large-scale field study on the durability of polymeric membrane
roofing, engineers at Sarnafil International AG investigated the flat roof of the
Festspielhaus (opera house) in Bregenz, Austria. The results of the tests
performed on the field samples could very well surprise both architect and owner.
The findings confirmed the high expectations of the construction professionals.
The first opera festival in Bregenz took place in 1946 on the shore of Lake Constance. On two gravel
barges, accompanied by the Vienna Symphony Orchestra, Mozart’s early work BASTIEN AND
BASTIENNE was performed. Today one could hardly imagine any international festival calendar
missing the name Bregenz Festival.
At the end of the 1970’s the Bregenz Festival fulfilled a long-held wish: a new opera house with
convention centre was created as a second focus.
The building, designed by architect Willibald Braun Jr., featured a lightly sloped roof. Securing the
roofing assembly by ballasting would have entailed extra construction and work. And the roof pitch
was too shallow to allow covering with shingles or tiles.
The architect chose a progressive approach: He had the entire roofing assembly loose-laid and then
secured to the deck with linear mechanical fasteners. The roofing supplier designed the fastening
system specifically for the project – to perfectly suit the roof form and size and to withstand the
expected wind forces. Sarnafil S 327-12 was chosen as the roofing membrane. Construction of the
opera house and convention centre was completed in 1978.
Predicting the service life of a roofing membrane is based on extensive laboratory testing, specifically
pre-service accelerated aging tests. Based on the results, significant statements about life expectancy
can be made. These predictions can be confirmed only after a period of exposure to actual weather
Life-span, or service life, is one of the most important evaluation criteria in a life-cycle analysis. The
roofing system of the Bregenz opera house boasts a broad array of ecological and economical
advantages – the profile is hard to equal.
Today, after 25 years of service, the polymeric roofing membrane is in exceptional condition. It still
tightly hugs the substrate – in roof fields, at penetrations, at connections to protruding construction.
One gets the impression of a recently installed roof. And what appears evident to the naked eye is
confirmed by tests on membrane samples taken from the roof.
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The roofing membrane is free of widespread stains. And it is flexible – almost like new material. This
first impression is reinforced by the measurements. In the laboratory the roofing samples were tested
according to various standards and compared to material in new condition. Among the properties
tested were elongation at break, tear resistance, and low-temperature flexibility.
• After 25 years the elongation at break and tear resistance still exceed by far the nominal values for
• Low-temperature flexibility still measures at –10° C, which after 25 years of exposure can be
considered very good.
It has been verified that the roofing membrane is in excellent condition. Based on the outstanding test
values one can expect that this roof, installed in 1978, will continue to protect the Festspiel- und
Kongresshaus Bregenz from wind and water for many years to come.
Highly satisfied with the roof installed in 1978, the owners chose to use Sarnafil polymeric membrane
again – for the roof of the addition built in 1966 by architects Helmut Dietrich and Much Untertrifaller.