Arborist Reports for Development Permits
If you require an arborist report as part of permit issuance, or you're wondering whether your project needs one before you get that far, this page explains what's required, what the report actually contains, and what separates a report that gets approved from one that generates follow-up requests and delays.
When is an arborist report required?
Across the Greater Toronto Area, arborist reports are triggered at multiple stages of the development and permitting process. The exact requirements depend on your municipality, your project type, and the trees on or near your site.
The most common triggers are:
Development applications. Site plan approval, minor variance, consent application, and rezoning submissions that affect trees on private property or adjacent properties will typically require an arborist report as part of the application package. Urban forestry staff at most GTA municipalities are formally consulted as part of site plan review.
Building permits near protected trees. In most GTA municipalities, any construction that may injure or affect a protected tree requires a permit, and that permit requires an arborist report. What counts as a "protected tree" varies by municipality: Toronto protects private trees at 30cm diameter and above; Oakville and Burlington protect trees at 15cm; Mississauga requires permits for trees 20cm and over involved in development. The threshold matters because even trees just outside your building footprint can fall within regulated protection zones.
Tree removal permits. If your project requires removing a tree that meets your municipality's size threshold, an arborist report documenting the tree's condition and providing justification for removal is part of the permit application. In Toronto, you'll need to submit both the arborist report and a tree protection plan as conditions of the permit.
Committee of Adjustment and Local Planning Appeal Body proceedings. If your application goes to committee or appeal, arborist evidence and reports become part of the record. Decision-makers at TLAB and CoA proceedings increasingly weigh tree preservation arguments when evaluating minor variances and consents.
Infill and intensification projects. Laneway suites, garden suites, additions, and lot severances on urban lots almost always encounter trees. On a typical 25 to 50-foot Toronto lot, there may be multiple bylaw-protected trees on or adjacent to the property, all requiring assessment before construction can begin.
When in doubt, assume you need one. The cost of an arborist report is insignificant compared to the cost of a stop-work order or a required redesign.
What’s included in a compliant arborist report?
An arborist report prepared for a development permit application is not a simple opinion letter. It's a technical document prepared in accordance with municipal requirements, ISA standards, and the specific conditions of your project.
A complete report for development purposes includes:
Tree inventory and survey. Every tree on the subject property and on adjacent properties within the zone of influence is identified, measured, and assessed. Species, diameter at breast height (DBH), condition rating, and structural status are documented for each tree. Toronto requires that arborists survey trees within 6 metres of the property line, and adjacent property trees within the zone of influence of proposed construction.
Assessment of construction impacts. The report evaluates how the proposed work will affect each tree. This includes calculating tree protection zones (TPZs), identifying where construction activity conflicts with those zones, and assessing root system impacts from grading, excavation, and underground services.
Preservation and removal recommendations. Each tree gets a recommendation: retain with protection, retain with mitigation measures, or remove. Recommendations for removal require justification based on tree condition, structural defects, or unavoidable conflict with approved development.
Tree protection plan (TPP). For development applications, an arborist report is typically accompanied by or integrated with a tree protection plan that shows the location of protective fencing, hoarding specifications, construction staging areas, and any required mitigation measures. In Toronto, the TPP is a formal submission requirement.
Mitigation specifications. When construction must occur within a tree protection zone, the report specifies how that work should be done: root pruning methodology, grade change techniques, soil aeration, construction timing, and supervision requirements.
Replacement and compensation. If tree removal is approved, most municipalities require a replanting plan. The number and size of replacement trees is calculated based on the value of the removed tree and municipal compensation ratios.
The report must be signed and sealed by a qualified arborist. Most GTA municipalities specify that the arborist must be ISA certified at minimum. For complex sites or where reports may face scrutiny at committee, BCMA-level credentials provide a higher standard of documentation.
What makes a report hold up to municipal review?
This is where the difference between a generic report and a defensible report becomes consequential.
Municipal urban forestry staff review arborist reports critically. They're looking for gaps, inconsistencies, and reports that apply cookie-cutter language to site-specific situations. A report that doesn't address the actual conditions on your site, or that uses imprecise language around protection measures, generates comments and requests for revisions. In a development timeline, those revisions cost weeks.
Reports that survive municipal review share a few characteristics.
They're site-specific. Every tree is individually assessed and addressed. Generic statements about "trees will be protected" don't satisfy urban forestry staff who need to see exactly how each tree will be protected.
They're written by someone with both credentials and field experience. The BCMA designation is the highest credential in arboriculture, held by fewer than 40 arborists in Ontario. It matters not just for the credential itself, but because the exam and experience requirements behind it reflect a depth of knowledge that shows up in report quality. Equally important: recommendations in an arborist report need to be grounded in an understanding of what's actually achievable during construction. A consultant who has never been in the field designing and implementing protection measures writes different reports than one who has.
They address the municipality's specific submission requirements. Toronto, Hamilton, Oakville, Mississauga, and Burlington all have different requirements for what must appear in an arborist report. A report prepared for one municipality and submitted to another without adjustment is a common source of delay.
They anticipate staff concerns. An experienced consultant knows what urban forestry staff are likely to flag. Addressing those concerns proactively, rather than waiting for a comment letter, compresses the review timeline.
Common mistakes that delay approvals
Submitting before the arborist has reviewed the design drawings. The arborist needs to see the proposed grading plan, underground services, and building footprint to properly assess construction impacts. Reports prepared without this information are frequently returned with requests for revision once design drawings are submitted.
Under-surveying adjacent trees. Trees on neighbouring properties that fall within the zone of influence of construction need to be assessed. Missing them is a common reason for incomplete application notices.
Vague protection specifications. Stating that "tree protection fencing will be installed" without specifying location, type, and extent is insufficient. Urban forestry staff need to see exactly where the hoarding goes.
Credentials mismatch. Some municipalities specify minimum credential requirements for arborist reports. An uncertified or lower-credential report submitted to a municipality that requires ISA Certified Arborist sign-off will be rejected outright.
Late engagement. Bringing in an arborist after the design is complete creates unnecessary conflict. Trees that could have been preserved with a minor design adjustment become removal targets because the design didn't account for them. Arborist involvement at concept stage, before drawings are finalized, is always the better approach.
How the process works
Every project is different, but the general sequence for a development arborist report follows this pattern:
An initial conversation establishes what you're working with: project type, municipality, stage in the approvals process, and what you know about the trees on site. That conversation is free and typically takes 20 minutes.
A site assessment follows, where I survey and assess all trees within the zone of influence, review the proposed design drawings, identify conflicts, and assess options. For most urban infill projects, this is a half to full day of field work.
The report is prepared, reviewed against the specific municipal submission requirements, and delivered. Turnaround for standard development arborist reports is typically five to seven business days from site visit completion, though urgent timelines can often be accommodated.
I provide direct support through the review process if comments come back from urban forestry staff.
If your project requires a tree protection plan, pre-construction pruning, or construction monitoring in addition to the report, those services integrate directly into the same engagement.