Tree Root Protection Guidance
The principles of tree root protection are set out in BS 5837:2012 Trees on construction sites, and Arboricultural Practice Note 12 (APN 12) “Through the trees to development” published by the Arboricultural Advisory and Information service.
These documents recommend that no excavation is undertaken over the area of the tree’s root ball, and suggests that a cellular confinement system is used to retain a no-fines sub-base material and distribute load to the ground beneath.
This system will allow rainfall and oxygen to infiltrate to, and harmful gases to escape from, the underlying soil. As a minimum, it recommends that a geotextile separator is placed beneath the geocell and sub-base; where additional reinforcement is required on weak ground a geogrid may additionally be required.