Tree Protection Zones in Toronto: How They're Calculated

What a Tree Protection Zone Is

A tree protection zone (TPZ) is the buffer around a tree, measured outward from the base of the trunk, where Toronto Urban Forestry prohibits excavation, grading, material storage, equipment traffic, and anything else that could injure the trunk, canopy, or roots. It applies to trees protected under the Private Tree By-law (Municipal Code Chapter 813), to trees on City streets, and to trees in areas regulated under the Ravine and Natural Feature Protection By-law (Chapter 658).

The TPZ is a minimum. Urban Forestry's own policy notes that the published distances protect a tree's anchor and transport roots, but feeder roots responsible for water and nutrient absorption can extend beyond that boundary. Depending on the tree and the site, the City can require a larger zone than the table below sets out.

Hoarding and Fencing Requirements

Urban Forestry's specification calls for plywood tree protection hoarding, minimum 19 mm (three-quarter inch) thick, built 2.4 metres (8 feet) high, installed at the TPZ boundary shown on the approved tree protection plan. The height can come down where low branches require it, or where Urban Forestry approves an alternative. Within a City road allowance where visibility is a concern, 1.2 metre (4 foot) high orange plastic web snow fencing on a 38 x 89 mm (2 x 4 inch) frame is used instead of solid hoarding.

Each barrier needs a sign, minimum 40 cm by 60 cm, mounted on all sides, identifying the area as a tree protection zone and warning that grade alteration, excavation, compaction, material or equipment storage, liquid disposal, and vehicle traffic are not permitted inside it.

Where the full minimum TPZ cannot be met because of site constraints, Urban Forestry can accept horizontal, on-grade root protection instead, designed by a qualified professional and approved before installation. On private property the hoarding is plywood, not oriented strand board. District service counters hand out the tree protection zone signs for free. The hoarding goes up before the tree permit issues. Once it is up, email the Urban Forestry planner photos that show the inside and outside of each protection zone and how the hoarding is built, including any horizontal protection. The planner approves from the photos or visits the site, and the permit issues after that approval. Our tree protection and fencing service installs to these specifications and photographs the installation for that approval.

What a TPZ Means for a Construction Project

Once a TPZ boundary is established, almost everything a construction site normally does is off-limits inside it. Urban Forestry's list of prohibited activities includes:

• Building, demolishing, or altering any structure, driveway, patio, deck, pool, or retaining wall
• Excavating, trenching, or changing grade by adding or removing soil
• Storing construction materials, equipment, or debris
• Discharging concrete sluice, paint, oil, or pool water where it can reach the root zone
• Parking or moving vehicles and equipment
• Cutting, exposing, or stripping roots, trunk, or branches

Calculate the TPZ before you finalize a design. A foundation, driveway, or excavation footprint that lands inside the zone forces a redesign, a request to Urban Forestry to reduce the TPZ with alternate protection measures, or root pruning supervised by an arborist. Getting the number right at the planning stage avoids a permit application bouncing back for a corrected tree protection plan. Our guide to building or landscaping near a protected tree covers what counts as encroachment on an active site and what to do when the TPZ does not fit the lot.

The TPZ calculation itself is one of the six components Urban Forestry checks in a construction arborist report. A mismatch between the fencing shown on the plan drawing and the DBH-based distance in the written report is a common reason Urban Forestry sends a submission back.

Frequently Asked Questions

What is a tree protection zone in Toronto?

A tree protection zone (TPZ) is the area around a tree, measured from the outside edge of the trunk base, where the City of Toronto prohibits excavation, grading, material storage, equipment access, and any other activity that could damage the trunk, canopy, or roots. It applies to trees on City streets and private property protected under the Private Tree By-law, and to trees in areas regulated under the Ravine and Natural Feature Protection By-law. The boundary is marked on site with a physical barrier before construction starts.

How is a tree protection zone calculated in Toronto?

Toronto Urban Forestry sets the minimum TPZ radius from a table keyed to the tree's diameter at breast height (DBH), measured at 1.4 metres above ground. The radius increases in 0.6 metre steps as DBH increases, starting at 1.2 m for trees under 10 cm and reaching 6.0 m for trees between 91 and 100 cm. For trees over 100 cm DBH, the formula becomes 6 cm of protection radius for every 1 cm of diameter. Ravine trees get double these distances, or the drip line if that extends further. These are minimums. Urban Forestry can require a larger TPZ for a given tree and site.

What is the minimum tree protection zone for a 40 cm tree in Toronto?

A tree with a diameter at breast height between 30 and 40 cm falls into the 2.4 metre minimum protection distance band under Toronto's Table 1. If that same tree sits in a Ravine and Natural Feature Protection area, the minimum becomes the drip line or 4.8 metres, whichever is greater.

When can tree protection fencing come down in Toronto?

Not until the Urban Forestry planner on the file confirms in writing that it can come down. Hoarding stays up until all work near the tree is finished, decks and patios included. Then email the planner photos of the protected trees and the hoarding. Staff approve removal from the photos or after a site visit. Toronto asks for no arborist close-out report for this step. Removing the fencing before that approval is a bylaw contravention regardless of how far construction has progressed.