Tree Protection Zones


What if paving could be 98% permeable? Absorb stormwater with zero runoff. Strong enough to carry heavy loads. No potholes, puddles, cracks. Modular, fast, easy-to-install.  Naturally attractive with gravel or grass fill. Environmentally Sustainable. A natural water filter. Paving that saves land & money vs. concrete. Eliminates detention ponds & flooding. TRUEGRID permeable pavers are the smarter paving alternative to concrete and asphalt.


Protecting The Urban Tree Canopy


Whether a tree is on Private Land or Public Land various regulatory authorities are engaged in approval roles with the aim to protect the Urban Forest. At TRUEGRID we see the Urban Forest as all the trees in built‑up urban areas including the vegetation, soil and water that supports them. They are a critical part of what makes our towns and cities a more enjoyable place to live, work and play.

As a proud member of TREENET we engage with the community to implement a range of products that are capable of delivering adequate quality and quantity of space for tree root growth with our patented commercial permeable pavers.

What is a Tree Protection Zone (TPZ)?


The Protection of trees on development sites is defined by local council regulation drawn from the Australian Standards AS 4970—2009. The TPZ is a combination of the root area and crown area requiring protection. It is an area isolated from construction disturbance, so that the tree remains viable.


Australian Standards AS 4970—2009

How to Calculate a Tree Protection Zone?


The size of the TPZ will be defined by the consulting Arborist who will nominate the area to be protected from soil compaction and root damage on either a temporary or permanent basis.

During construction works the instillation of a temporary fence and signage around the designated area is the most accepted method to create an environmental preserve.


Penrith City Council

This type of protection is not always achievable as equipment may require access through the area given a lack of space or the location of works. AS 4970—2009 Section 4.5.3 allows for Ground Protection measures to be installed to prevent soil compaction and root damage within the TPZ.

Australian Standards AS 4970—2009

These measures may include placing a permeable geofabric on the ground to cover the surface, placing a layer of mulch or crushed rock 150mm thick and then protecting this surface below a Rumble board or similar.

TRUEGRID Pro Plus S Flex 48 can be installed in place of the Rumble Boards and either filled with mulch or crushed rock to provide a Drive on Surface for any vehicle. At the completion of the project the TRUEGRID can be picked up and restored on pallets for reuse or if no future reuse TRUEGRID can be fully recycled.

Creating Permanent Protection For Trees In Commercial, Industrial And Public Sector Car Parks

For more permanent solutions TRUEGRID can be used as a part of the Tree Protection Management Plan in the same way it can replace temporary rumble boards based on the cross section detailed below. The depth of the angular gravel subbase will be determined by the depth of roots to be protected and the vehicle load to be carried.

TRUEGRID Commercial Permeable paving delivers a Drive on surface for any vehicle load, stormwater quality and quantity benefits, enhanced ecosystem services, and reduced tree root impacts.

The 2023 TREENET Engineering for Trees Presentation by Russel King concluded that Pavement surfaces are damaged when forces exerted by radially expanding tree roots exceed the shear strength of subgrades, pavement base materials, or the wearing surface.

A layer of gravel has been demonstrated to deter tree root growth (Cline et al., 1980; Hakonson, 1986; Reynolds, 1990, Gilman 2006), and gravel used for structural and stormwater detention purposes beneath permeable paving has shown a similar root-deterrent benefit in experiments conducted in Adelaide (Johnson et al. 2019) and on the Sunshine Coast (Lucke and Beecham 2019).

The highly porous gravel base protects the pavement assets and the trees; it provides stormwater detention volume to increase infiltration to nurture trees, and it supports seasonal drying of the gravel base and the subgrade surface which suppresses shallow root growth. https://treenet.org/resource/engineering-for-trees/

“TRUEGRID is  important to bridge the requirement for hard landscaping such as building carparks while still being able to maintain the natural soil area beneath. This can reduce the amount of trees needing to be removed.” Andrew Stovell Redland Tree service