Abstract

The service life of roofs depends not only on the quality of materials and components but also on several other factors such as workmanship, maintenance, design and substrate. The service life of materials is at production time estimated to a certain number of years. Later when some experience has been gained the service life can hopefully be better predicted. However, the predicted service life can always be questioned because no one knows how long the product or material will last. The durability of a two-layer roofing-felt membrane has been investigated through inspection of several 20 to 30 years old roofs that had aged naturally under in use conditions in a northern humid climate. In 50 % of the inspected roofs, samples were taken out for laboratory test. In this paper, the developed methodology to conduct a service life prediction of roofing membrane is presented. The paper includes a description of the on-site inspection; test conducted in the laboratory which was used as basis for predicting the service life of the two-layer roofing-felt membrane and how these information are extrapolated to a predicted service life. Further, it is discussed if the used methodology for prediction is generally applicable for other types of membranes.