FLL (Landscape Research, Development and Construction Society)

The Forschungsgesellschaft Landschaftsentwicklung Landschaftsbau e.V. (FLL), in English the Landscape Research, Development and Construction Society, is a German non-profit association founded in 1975. It is based in Bonn and produces technical guidelines for landscaping and building greening. Its website is fll.de.

Role

FLL brings together experts from industry, research, public authorities and professional bodies in committees that write guidelines (Regelwerke) on topics such as landscape construction, tree care, playgrounds, sports grounds and the greening of buildings. A committee on building greening (Bauwerksbegrünung) handles green roofs and green facades.

Green roof guidelines

FLL's guidelines for the planning, construction and maintenance of green roofs (Dachbegrünungsrichtlinie) have become one of the most widely cited green roof references in the world. They have been revised several times and translated into English. Topics include:

• types of green roof (extensive, simple intensive and intensive) and suitable plants;
• requirements for growing media, such as particle size, water retention, organic content and weight;
• drainage and filter layers;
• protection against root penetration, including a test method used to certify root-resistant membranes and root barriers;
• roof slope, wind uplift and fire precautions;
• care and maintenance during establishment and in later years.

Waterproofing membranes sold in Europe and beyond are often described as root resistant according to the FLL test.

Influence

Because Germany was an early adopter of modern green roofs, many other countries, including in North America and Asia, based their first green roof guidance on FLL documents. They are used alongside national roofing rules, such as those of the German roofing trade, and standards such as EN 13948 for root penetration.

Related bodies

The European Federation of Green Roof and Green Wall Associations (EFB) and North America's Green Roofs for Healthy Cities draw on FLL guidance in their training and publications.