460 STRUCTURAL ELEMENTS AND BUILDING METHODS GREEN ROOFS a b
Fig. 3.14.16: Flat roof renovation: a) condition before renovation, b) following green roof implementation
Fig. 3.14.17: Sloping green roof
Fig. 3.14.20: Intensive sloping green roof with turf and integrated guttering
Roof incline and pitch
Depending on steepness, measures relating to water retention and delivery as well as slippage prevention should be put in place for sloping roofs with a 5–58% incline. These begin with shear barriers at drainage level and extend to the upper vegetation layer, with erosion resistant weaves or similar measures. For more demanding vegetation types and intensive utilization, rooftop irrigation should be put in place. In principle, a variety of green roof forms are possible given careful planning. > Figs. 3.14.17–3.14.21
Roof incline is an important technical consideration in choosing a green roof. Roofs with 0–2% roof incline are particularly suited to intensive green roofs with wateraccumulation irrigation. Tolerances in building construction do not preclude puddles forming at the drainage layer. For this reason, the roof seal should be laid to measure especially and a drainage level should always be provided (the same applies to extensive green roofs!). Roofs with 2–5% incline are generally optimal for green roofs and are also favorable for water retention. Where water accumulation irrigation is in place, water accumulation thresholds may have to be provided. The roof pitch means that excess water quickly flows out of the drainage system. Where construction tolerances permit a siphon effect or insufficient downward water movement, these must be eliminated.
Watering and drainage systems The number and placement of drainage installations such as roof drains, roof guttering, water spouts, and emergency overflows is a function of the structure’s pitch and the green roof’s construction. Roof drains on the roof skin should be designed to be visible via
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roof planting structure (extensive): 1 vegetation mat 2 approx. 8 cm extensive substrate 3 anti-slippage system 4 drainage mat 5 superstructure (warm roof): roof seal (root-proof) thermal insulation vapor seal reinforced concrete Fig. 3.14.18: Standard extensive sloping roof construction
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roof planting structure (intensive): 1 pre-cultivated turf 2 rooting fabric 3 approx. 17 cm lawn substrate 4 anti-slippage system 5 protection for structure and drainage mat 6 separation and sliding membrane 7 superstructure (waterproof concrete roof): bituminous adhesive seal waterproof concrete Fig. 3.14.19: Standard sloping roof lawn construction
Fig. 3.14.21: Installing a claw mat to prevent slippage