If you’re planning a garden or laneway suite, the mature tree at the back of your lot may be the thing that stops it. The city won’t issue the building permit if it can’t first issue a tree permit, and if the tree is healthy, that permit may be refused. The single most useful thing you can do at the design stage is bring an arborist in before the footprint is committed.
Not Every Backyard Tree Is Protected
A private tree is protected under Chapter 813 of Toronto’s Municipal Code when its trunk is 30 cm or more in diameter, measured at 1.4 metres above ground. That’s roughly the size of a mature backyard maple that’s been growing for 20 years. If nothing near your build site is close to that, the conflict described in this post may not apply to you.
Two exceptions to that threshold: if your lot falls in a ravine or natural feature protection area, Chapter 658 covers trees of any size. And street trees require a permit regardless of trunk size, no matter where the trunk sits.
The City’s Position on Suites and Healthy Trees
Garden suites became as-of-right (allowed by default, no rezoning or special approval needed) in Toronto under By-laws 100-2022 and 101-2022. Laneway suites were legalized earlier, through Toronto’s 2019 zoning amendments. The city’s stated goal for the suite program includes maintaining permeable space and expanding the tree canopy.
On a lot with mature trees, that goal and the footprint of a new dwelling unit can work directly against each other. The city’s guidance is direct: a garden suite “should not result in the removal of a healthy by-law protected tree.” The same standard applies to laneway suites. If your proposed design requires removing a healthy protected tree, the city can refuse the tree permit under Chapters 658 and 813 of the Municipal Code. Without the tree permit, the building permit doesn’t proceed.
What “Protected” Actually Covers
The 30 cm trunk threshold is the entry point, but protection extends beyond the trunk. Any construction that affects a tree’s protection zone (TPZ) requires a permit, even if the tree is staying put. The permit to injure covers that scenario. TPZ radius scales with trunk size: 2.4 metres for a tree in the 30 to 40 cm range, 3.0 metres for 41 to 50 cm, and 3.6 metres for 51 to 60 cm. On ravine-regulated lots, those radii double.
If your lot or the adjacent lane falls in a ravine protection zone, check the “Ravine and Natural Feature Protection By-law” layer in the city’s interactive map tool.
Where the Zoning and the Trees Collide
Zoning fixes the box where you can build. The tree bylaw draws a no-disturb ring around each trunk. On a typical Toronto lot with one or two mature trees, those two overlap.
Garden suite geometry, in brief:
- Minimum rear yard setback: 1.5 metres
- Minimum separation from the main dwelling: 5.0 metres (7.5 metres for suites taller than 4.0 metres)
- Maximum footprint: 40% of the rear yard area or 60.0 sq m, whichever is smaller
- Rear yard soft landscaping requirement: at least 50% on a standard lot
Laneway suites get up to 10.0 metres long and 8.0 metres wide. The rear wall can sit at a 0.0 metre setback when it has no openings and doesn’t abut a street or lane. Trees along the lane side of a rear yard push the footprint further forward and straight into the separation distance from the main house. Combined ancillary lot coverage is capped at 30%.
One constraint that surfaces late in the process: emergency access. The path from the public street to a garden suite entrance must be at most 45 metres long, at least 1.0 metre wide, and have 2.1 metres of vertical clearance, unobstructed. A mature low-branching tree along the side passage can fail that test and force a design change.
This is exactly the conflict an arborist maps before you commit the footprint. A construction arborist report done at the design stage leaves room to adjust. Done after the drawings are locked, it becomes documentation for a dispute you may not win.
The Permit, Replacement, and Timeline Picture
Costs and timing, together:
- Permit fees: $436.39 per tree for a private tree permit. If the tree is shared with a neighbour, it’s classified as a boundary tree and the fee rises to $913.58
- Review timeline: Toronto does not publish a standard review time in its current application guidance. A request for revisions or additional information extends the project timeline
- Replacement obligation: Chapter 813 requires one replacement tree for every 10 cm of the removed tree’s trunk diameter. Because a protected tree is at least 30 cm, that’s a minimum of three replacements. A 50 cm tree means five
- Cash-in-lieu: $583 per required replacement tree, not per tree removed, when on-site planting isn’t feasible. Staff are increasingly reluctant to accept it where they determine planting space exists
See the full replanting breakdown in our post on replanting requirements and cash-in-lieu across the GTA.
Replacement trees planted as a condition of a permit will be protected from the day they go in the ground, with no size threshold or waiting period, beginning September 1, 2026. Full details are in our post on Toronto’s September 2026 tree bylaw amendments.
When Removal May Be Approved
A tree that is declining, structurally compromised, or dead is a candidate for removal. A healthy tree in an inconvenient location is a much harder case. Removal because the tree blocks the preferred footprint is a weak basis for a permit application.
One additional threshold: starting September 1, 2026, any tree with a trunk greater than 61 cm in diameter is eligible for Distinctive Tree designation. The city must consider whether any tree in a permit application qualifies, and may refuse a permit to injure or remove a Distinctive Tree. It’s not an automatic refusal, but a suite proposal involving a tree that size will face a higher bar.
Getting the Arborist Report Right for Your Suite Project
Our team prepares construction arborist reports for garden suite and laneway suite applications across Toronto. The report documents every protected tree within and adjacent to the construction envelope, assesses root zone impact, and produces a tree protection plan drawn to the same geometry as your building permit drawings.
If you’re in the design phase, an early site visit can clarify the constraint picture before the footprint is committed. If the drawings are done, we work from the existing design and identify where the conflict points are. Contact us with your address and the current stage of your project and we can confirm the scope before we visit.