Root barrierAn effective root barrier is crucial, both in case of extensive and intensive roof vegetation, to prevent damage of roof’s sealing caused by penetrating roots.
For this purpose single or double layer materials are used. They usually constitute an effective barrier for roots. They take form of roof foils or membranes made of plastic. Double-layer coverings consist of min. 4mm of undercoat layer and of min. 5mm of top layer.
Both types of layers are manufactured with the use of SBS polymer modifi ed bitumen. In bitumen materials, resistance to overgrowing roots is obtained by addition of a special chemical substance or a copper foil insert. Roof coverings must be installed in accordance with manufacturer’s instructions, or with appropriate regulations.
100% of weather tightness is a necessary condition if a green roof is to be installed.
- intensive vegetation regularly irrigated and carefully maintained with a thick layer of substrate is treated as a fi re-retardant covering,
- extensive vegetation should be treated as suffi ciently fi re-retardant (fi re spread and heat radiation) if it has the following characteristics:
- defined mineral content of the bearing vegetation layer minimal thickness 3 cm,
- low fi re load of vegetation forms,
- bigger areas must be fi re-separated with either gravel or concrete slabs every 40 meters.
Wind-caused hazardsDue to operation of wind, buildings are subject to the activity of contact forces and wind suction forces. Their intensity depends on the direction of wind and on building’s construction and height. Wind load on the roof can cause damage during installation works and after the roof is ready. Surface of the roof has been divided into three areas depending on the level of hazards connected with wind load:
- area exposed to hazard with a big load,
- roof’s verge area with a big load,
- roof’s middle area with a small load.
Each area of the roof should be properly protected with the use of adequate means. In areas exposed to hazard and in the roof’s verge area, gravel ballast and anti-buoyancy concrete slabs should be used.
Codependency between vegetation form and the thickness of the vegetation layer is portrayed in the following scheme: