Tree Protection Zones

by Aug 24, 2016Home Addition Tips

Have you ever seen a fence surrounding a tree when construction is taking place on a property? If you have, you noticed a tree protection zone (TPZ), and they are needed on construction sites that have trees on the property.

Homeowners that are doing a substantial renovation need to understand when a tree needs to be protected, and when you have to deal with it in the planning process of building a house.

When you are planning to do a major renovation to your home, you will have to apply for permit drawings once your architect has all of the necessary drawings put together. When urban forestry looks into your property for potential TPZ’s for the renovation, they designate trees to have a certain protection zone around them based on two main things; the tree diameter, and if they are city-owned or private trees. Below is the table that urban forestry uses as the minimum guidelines for protecting a tree:

tree protection guidelines

You may notice the third column that talks about a tree’s dripline. The dripline of a tree is essentially the distance from the tree trunk where water falls off of the tree onto the ground around it, much like how an umbrella drips water around you when you are under it. Usually most construction is not done near ravines or nature feature protection areas so the third column does not usually apply to the most Toronto-area residents.

The next thing to figure out is whether your trees are city-owned or private, because this could be the difference between protecting all of your trees or none of them. When you have private trees, you do not need to protect them unless they are 30 cm or above in tree diameter. City-owned trees differ because they all need to be protected no matter what the size is (even if they are smaller than 10 cm). James Mohlmann, a Forestry Standards Officer for the city of Toronto cited the difference as, “If the tree is located on municipal property such as a privately owned residential address with a fronting municipal allowance where at  least 50% of the tree’s base is on city property, it would be deemed city-owned. This includes parklands and other municipally owned property throughout the city.”

James went on to talk about when an arborist report is needed in the process of building a home, and he said, “It is recommended that an arborist is consulted before site plans are finalized, inventorying trees on or adjacent to the site, and identifying tree concerns that can be addressed before the drawings are finalized.  Ultimately the arborist report/tree preservation plan will be reviewed if applications for injury or removal are necessary.”

Another important part of the tree protection zone is knowing what is not allowed to happen within the area. Within a Tree Protection Zone (TPZ) there must be:

  • no alteration or disturbance to existing grade of any kind;
  • no changes to the grade by adding fill, excavating or scraping;
  • no storage of construction materials or equipment;
  • no storage of soil, construction waste or debris;
  • no disposal of any liquids e.g. concrete sleuth, gas, oil, paint; and
  • no movement of vehicles, equipment or pedestrians.

Since a fence should be put around the TPZ, none of this will likely happen if your home builder knows what they are doing.



Ryan Meagher, Guest Blogger, BVM Contracting - Home Addition and Home Renovation Contractor.

About the Author

Ryan Meagher

Business Development, BVM Contracting

A graduate of chemical engineering from Queen's University, Ryan has spent many summers working with BVM Contracting in various roles and projects. This experience has provided him with a unique view on the residential construction industry which he loves sharing with you!