As their names clearly indicate, roof gardens are essentially established on the roofs of buildings. Although roof gardens are popular in the present world, they have actually been around for many centuries. The ancient gardens were prepared in pyramid designs on top of elaborate rooms.

Ancient Babylonian Hanging Gardens

The roof gardens can be traced back to the reign of King Nebuchadnezzar of Egypt. The king established hanging gardens to please Queen Semiramis by 600 B.C. The gardens were terraced and set over elaborate rooms in set pyramids. Arcaded structure provided support for the gardens, which were arranged in form of ascending terraces. They were built over staterooms from which they were separated using brick tiles, natural asphalt, lead and reed.

Apart from providing breathtaking beauty, the roof gardens allowed the royal family to have private outdoor gardens. These are still some of the main reasons why people consider roof gardens nowadays but there are many others, including ecological considerations.

A series of earthquakes later destroyed the Babylonian hanging gardens.

The Renaissance

The Renaissance era brought a renewed interest in roof gardens, particularly in Rome and Greece. The gardens provided fashionable designs for the rich. For example, Cosimo de Medici, a Florentine ruler, established ornate roof gardens where he planted rare plants collected from different places.

Other notable gardens were the Cremlin Palace Gardens in Moscow and Aztec City Gardens.

Establishing gardens over various structures, ranging from grottoes to palaces, became popular during this period, something that caught on up to England and Northern Europe.

19th Century Innovations

The earlier roof gardens were established on sloped surfaces to enhance drainage. However, waterproofing techniques developed in the 19th century made it possible to establish the gardens on flat roofs.

Carol Rabbitz, a German builder, prepared the first of such gardens on the roof of his own house in Berlin towards the end of the 19th century. He constructed a waterproof barrier that separated his house from the top floor using vulcanized cement he had invented. The Paris World Exhibition held in 1867 displayed a model of Carol’s house.

20th Century Developments

Further developments were carried out at the start of the 20th century, such as the use of petroleum-based products for waterproofing, which made it possible to established relatively large roof gardens.

Many architects adopted roof garden designs, including Frank Lloyd Wright, Le Corbusier and Roberto Burle Marx. The Kensington Roof Garden is among the famous roof gardens of the era. The garden was built on top of a London department store and its construction was completed in 1938. It included several themed gardens featuring trees, shrubs, roses and perennials and water features where ducks and flamingoes were found.

Other popular gardens of the time include the Rockefeller Gardens in New York, Toms and Derry Garden and Union Square Garden in San Francisco.

The Modern Era

Roof gardens are currently more popular because of ecological factors; hence they are also known as “green roofs.” These gardens largely feature specimen plants planted directly on soil placed on the roofs, with waterproof barriers separating the lower spaces. The earlier gardens were mostly composed of specimen planted in containers placed on the roofs.

There are two main types of green roofs:

• Extensive gardens featuring thin layers of soil supporting different meadow plants.

• Intensive gardens with thick layers of soil that generally support trees, shrubs and perennials.