If there is a protected tree anywhere near your planned addition, deck, pool, or laneway suite, draw the tree protection zone around it before you finalize the design. Everything a construction site normally does inside that zone is prohibited.
The tree protection zone (TPZ) is a fixed distance set by trunk diameter, and Toronto’s Urban Forestry department checks proposed construction against it before it issues a tree permit.
Trunk Size Sets the Zone
Toronto calculates the minimum TPZ from the tree’s diameter at breast height (DBH), measured at 1.4 metres above ground. A tree between 30 and 40 cm DBH needs a 2.4 metre buffer measured from the outside edge of the trunk. That distance climbs in steps as the tree gets bigger, up to 6.0 metres for a tree between 91 and 100 cm, and beyond that the formula switches to 6 cm of radius for every 1 cm of diameter. If the tree sits in a Ravine and Natural Feature Protection area, the minimum doubles, or extends to the drip line if that reaches further.
Urban Forestry flags any footprint that overlaps the TPZ.
What Counts as Encroachment
Once the TPZ boundary is established, the list of prohibited activity inside it is long and covers most of what a build site does day to day: excavating or changing grade, storing materials or equipment, parking or moving vehicles, discharging concrete sluice or paint where it can reach the roots, and cutting or exposing roots, trunk, or branches. Building or altering a structure, driveway, patio, deck, pool, or retaining wall inside the zone is off-limits without a separate approval.
A contractor staging lumber against the fence line, a skid steer parking inside the zone between tasks, or a downspout redirected to drain across the TPZ during a wet week are all encroachments, even when nobody touches the tree directly. Urban Forestry counts deliberate root cutting and incidental site traffic the same way, as interference with a protected tree.
Why Forestry Wants an Arborist Report With a TPZ Plan
Because the zone has legal weight, Toronto’s Urban Forestry department reviews a construction arborist report with a tree protection plan attached before it issues a permit for work that injures or removes a protected tree. That tree permit is its own application with its own fee, and Urban Forestry issues it after the building permit is approved. The report identifies every affected tree, calculates its TPZ, and assesses how the proposed construction will affect its root zone and canopy. The plan is the scaled drawing that shows exactly where the fencing goes, so a site inspector can check it against the site rather than against a written description.
A tree removal tied to construction costs $436.39 per tree, compared with $145.87 for a standard removal not tied to construction. The higher fee pays for the more involved forestry review.
A design that has not accounted for the TPZ is a common reason a submission gets sent back. If the fencing shown on the drawing does not match the DBH-based distance in the written report, or the proposed footprint clips the zone with no mitigation plan attached, forestry holds the file until it is corrected. Calculate the TPZ before the design is locked in to avoid that correction cycle.
What Happens to Your Permit Application
The tree permit runs on its own track. If every protected tree stays fully protected, no Urban Forestry permit is needed, and the Tree Declaration form goes in with the building permit application. If the work injures or removes a protected tree, you apply to Urban Forestry separately. Staff ask for a copy of the approved building permit or zoning certificate before they issue the tree permit, and the tree permit allows the injury or removal only once the building or demolition permit is in hand and that work has started. Demolition can go ahead before the tree permit if the trees are fully hoarded.
Before the tree permit issues, the hoarding goes up and Urban Forestry approves it from photos or a site visit. When staff cannot tell from the report whether a tree survives the work, they ask for a root exploration first. That dig needs no permit, but it is an investigation only and must not injure the tree. Where a Committee of Adjustment decision carries tree conditions, Urban Forestry issues a separate clearance letter, covered in our guide to forestry clearance letters. That letter is not a tree permit.
Periodic site inspections during construction produce the record forestry wants at the other end of the project, when it is time to release the protection condition and let the fencing come down.
When the TPZ Does Not Fit the Lot
On a smaller urban lot, the minimum TPZ for a mature tree can eat into the buildable footprint more than the design allows for. Where the full TPZ cannot be met, Toronto’s specification lets Urban Forestry accept horizontal, on-grade root protection instead of the standard fenced buffer. A qualified professional must design it, and Urban Forestry must approve it before installation.
The other route is root pruning, done under an arborist’s supervision, to allow a reduced footprint without the unsupervised root damage that comes from a backhoe operator working blind. Either option needs to go through Urban Forestry before it appears on a permit drawing. Showing up with a reduced TPZ on the plans and no supporting approval is the same as ignoring the requirement altogether from the city’s point of view.
If a protected tree sits close to where you want to build, work out the TPZ and the options for it before the architect finalizes the drawings. Contact us with your address and what you are planning, and we will calculate the zone, flag any conflict early, and prepare the report Urban Forestry needs to release the permit.