Urban Trees - Technical Information
Raft systems
Raft systems are used to create a protective structural layer above tree root systems.
Typically installed to effectively create a load transfer platform that distributes concentrated loads (i.e. wheel loads) over a greater area, to protect the underlying soil structure. They may be infilled with granular material to provide additional structural raft rigidity, or when used beneath impermeable surfaces, they may be left open to provide an effective means of allowing the free movement of gases and water to the tree root system. Where appropriate detailing is used, they can also be utilised to introduce further organic matter into the system (e.g. ‘blowing’ leaf litter into the void created by the units).
Modular structures
Geocellular structures that have a high porosity and load bearing capacity, which are typically used to partially or completely replace aggregate and stone substrate.
The geocellular units support the imposed vehicle loading, while providing protection to a non-compactable zone that may be infilled with growing media. They may also be used to provide additional surface water attenuation storage, or through careful design, water retention that may be utilised for irrigation purposes.
