Green roof components

When designing a green roof, the components required will depend on the type of vegetation specified and how the balance between water retention and drainage is achieved to meet the demands of the vegetation. The general principle is to recreate the conditions nature provides in a shallower system. In all green roof scenarios, substrate depths are completely dependent on the vegetation specified and the different drainage / water retention layers are selected according to the levels of water required to be held within the construction.

Substrates

Generally the depth of substrate is dependant on the type of vegetation being installed. Low growing sedum will need a shallow, low nutrient, free draining substrate. Wildflowers will require deeper substrate (100-150 mm). Herbaceous plants, shrubs and trees on intensive green roofs will require greater depths (300-450 mm+). As planting becomes more substantial it is likely to require a higher organic content within the substrate. There need be no limit to the complexity of the landscape or recreational space.

Extensive Vegetation

Pre-grown SB and WB vegetation mats - these sedum and wildflower blankets will establish quickly and give high aesthetic finish immediately after installation.

Plug plants - enable particular species to be planted in particular locations. They require careful aftercare during establishment. Only recommended during the Spring or Autumn months.

Seed - offers a lower establishment cost but will normally take a couple of growing seasons to fully establish. Bauder produce a number of British Providence Seed Mixes for particular environments. The Bauder seed ranges all use seed sourced following the Flora Locale code of practice. The seed mixes are also rates as Perfect for Pollinates by the RHS. For a Biodiverse green roof, the various vegetation options above can be combined to help create different habitats.

Filter Layer

This layer is a polypropylene geotextile fleece that prevents substrate fines and sediment from being washed in to the water storage or drainage component. The pore size is around 0.13mm.

Water Storage / Drainage Layer

This layer helps to maintain the balance between the levels of water to be held on the roof to support the vegetation whilst allowing the surplus amount to drain away so that the substrate doesn’t become waterlogged.The water storage cells cells can be filled with gravel, type 1 or concrete to increase the compressive capabilities or as a bed for paving or other surface finishes. The components can be manufactured from a variety of materials such as high density polyethylene (HDPE) or polystyrene; each having their own reservoir capacity.

Protection Layer

This layer delivers protection against mechanical damage. As a general rule the more the roof is trafficked the higher the level of protection required, for example, extensive green roofs would generally experience much lower levels of traffic damage during maintenance than publicly accessed areas.

The Bauder protection layers are manufactured from the following materials:

• Eco Mat - recycled polyester and polypropylene.
• FSM 600 and FSM 1100 - polyester and polypropylene fibre mix.
• Pro Mat - recycled shredded rubber.