Historical green roofs: Their development until the invention of the iron concrete
Jana Ahrendt

This thesis concerns itself with a combination of nature and architecture in the form of roof gardens, which are poetically called “hanging gardens“. The topic is reflected only up to the time of the discovery of reinforced concrete at the end of the 19th Century. Up to this point there are only a few archaeological findings and literary descriptions of landscaped substructures or roofs, therefore much ambiguity exists. In addition this topic is missing in modern literature, thus there exists no summary of available information. This work serves to answer the following questions: On which type of sub-construction were historical roof gardens established? Which building materials were used for sealing under green belts? Which systems were installed for the irrigation of these high-lying gardens? How were these roof gardens equipped, with what plant and used for which occasions? Except for these practical questions, still another cultural question is asked: What motivated man over the ages to create gardens on roofs despite the incomprehensible difficulties and colossal costs? These questions are answered on the basis of examples from different continents and ages. For this purpose one hundred historical examples are catalogued in order to compare them in sequence of time and to draw conclusions from this. This continuous historical thread leads into the presence. It is of great importance and certainly worth examining the origins of the green roof which is so popular in present times. The history of green roofs began in Ancient Egypt, about four thousand years ago. It was continued during the Assyrian period and reached its height in Babylonian times with the hanging gardens of Semiramis (around 600 B.C.?). These gardens are probably the most famous example of roof gardens of all times. Although it is not a hundred percent certain that they really existed, they have inspired the fantasy of writers, artists and architects continuously since antiquity. Through this type of building Ancient Greece, Ancient Rome and Byzantine were particularly inspired, where roof gardens were not only an imperial privilege, but also widely used in private houses. After the brief low during the middle Ages hanging gardens reached their true bloom time during the Renaissance, when with the revival of antiquity the garden culture of the antique ages was also revived. The hanging gardens of the Renaissance were destined as demonstration of dominance of man over nature. During the time of classicism and romantics the green roof was made for the first time in its history the principle of a modern architecture, due to numerous drafts of the revolution architects. In the second half of the 19th Century contributed some modern inventions to constructions and materials for flat roofs to the fact that their establishment and landscaping were substantially facilitated. The discovery of reinforced concrete brought thereby the crucial break-through.