Frequently Asked Questions
about Green Roofs

Life expectancy

5. Which one has a higher life expectancy - a green roof or a gravel roof?

A professionally installed gravel roof has a life expectancy of 15-25 years.

The Fraunhofer Institute* calculated the life expectancy of a green roof to be more than 40 years. However, in practice green roofs in Berlin have shown they can protect roofs even after 100 years. (Handbuch der Architektur, Berlin, 1899)

How: A gravel covering provides limited protection from extreme environmental conditions which can impact the roof membrane and age it rapidly; whereas, the substrate and vegetation layers of a green roof provide protection for the waterproofing.

The additional layers of a green roof help to mediate extreme temperature differences; annual fluctuations are reduced from 212°F to only 95°F and daily fluctuations are reduced from 140°F to only 59°F. The build-up also provides protection from UV radiation, ozone, and mechanical damages, for example, hail, wind, maintenance works, etc. As a result the life of a roof is easily doubled.

* The ‘Fraunhofer Institute’ was established as a research organization in 1949 and was named after the successful researcher, inventor and entrepreneur Joseph von Fraunhofer (1787-1826). Today the institute is the largest organization for applied research in Europe.