Growth limit zone
The Electricity (Hazards from Trees) Regulations 2003 specify ‘zones’ which define the area around a power line which trees may not encroach.
There are two zones; the Growth Limit Zone and the Notice Zone, and the distances specified for each vary depending on the voltage of the power line.
Growth Limit Zone
This zone refers to the space around the power line which vegetation (trees) must not encroach on, even in windy or stormy conditions.
The Growth Limit Zone varies based on the voltage of the power line which the vegetation is in close proximity to.
| Voltage of Power Line | Growth Limit Zone |
| 33,000 volts (High Voltage) | 2.5 metres |
| 11,000 volts (High Voltage) | 1.6 metres |
| 400 volts/230 volts (Low Voltage) | 0.5 metres |
Notice Zone
This is one metre beyond the Growth Limit Zone.
The notice zone also varies based on the voltage of the power line which the vegetation is in close proximity to.
| Voltage of Power Line | Notice Zone |
| 33,000 volts (High Voltage) | 3.5 metres |
| 11,000 volts (High Voltage) | 2.6 metres |
| 400 volts/230 volts (Low Voltage) | 1.5 metres |
Controlled Access Zone
The Controlled Access Zone is four metres from any power line, and designates the area which must only be entered by a Unison-approved person.
If any part of a tree is within the Controlled Access Zone (four metres from any power line), an approved contractor must be used to cut or trim that tree.
The tree in this illustration will need to be cut or trimmed as it is inside the Growth Limit Zone. It is also within the Controlled Access Zone, so a Unison-approved person must be used to safely trim the tree.
| A | Growth limit zone |
| B | Notice Zone |
| C | Controlled Access Zone |