An arborist report is a formal written assessment of a tree prepared and signed by an ISA certified arborist. In Ontario, it is required by most municipalities as part of any application to remove or injure a protected tree. It is also required for tree preservation plans on construction sites, and it is the document insurance companies and lawyers rely on when tree damage is involved in a dispute. Here is exactly what the report covers and when you need one.
A formal arborist report prepared to Ontario municipal standards typically covers the following elements:
The report must be written in a form the municipality can use to make a permit decision. A clear, well-structured report from an experienced arborist moves through the permit process faster than a vague or incomplete one.
This is the most common reason for an arborist report in Ontario. Every major municipality in the GTA requires one as part of a private tree removal permit application:
When a building permit involves a property with protected trees, a Tree Assessment and Protection Plan (TAPP) or Tree Protection Plan (TPP) is required as a condition of the building permit. These are larger, more detailed documents than a standard removal permit report. They include a full tree inventory for the site, protection zone specifications, construction sequencing requirements and typically a commitment to monitoring visits during active construction.
If you are planning a home addition, garage, deck, or major landscaping project that brings construction activity within the protected root zone of a tree, you will likely need this document. Your arborist and your building permit application will both confirm the requirement for your specific project. See our full guide on tree protection plans for Toronto construction for more detail.
A hazard assessment is a specialized arborist report focused on structural risk rather than removal justification. It is used when a tree shows signs of potential failure, such as a lean, crack, extensive decay or root system compromise, and the property owner wants a professional opinion on the risk level and recommended action. Hazard assessments are often requested by insurance companies, property managers and legal counsel when a tree-related incident has occurred or is anticipated.
When a tree causes property damage or personal injury, an arborist report documents the condition of the tree at the time of or before the incident. This is important for insurance claims and for any legal dispute involving tree liability. A well-documented report from a qualified arborist is the foundation of any tree-related liability case.
Buyers of properties with large trees sometimes commission an arborist report as part of due diligence, particularly when trees are close to structures. Understanding the condition and permit status of significant trees on a property you are buying protects you from inheriting an expensive problem.
Our ISA certified arborist prepares reports for permit applications, hazard assessments and construction projects across Toronto and the GTA. Written in the format municipalities actually accept.
Arborist reports for municipal permit applications in Ontario must be prepared by an ISA certified arborist. The ISA (International Society of Arboriculture) is the internationally recognized professional body for tree care. Certification requires passing a written examination, demonstrating practical experience and maintaining ongoing education credits.
Reports from uncertified tree workers, landscapers or general contractors are not accepted by Toronto, Mississauga, Markham, Richmond Hill or other GTA municipalities with tree bylaws. Always ask for the arborist's ISA certification number before engaging them and verify it at the ISA website if you want to confirm it is active.
Some arborists also hold additional credentials such as Board Certified Master Arborist (BCMA) or Registered Consulting Arborist (RCA) designations, which reflect advanced training and experience. These are not required for standard permit reports but indicate a higher level of specialization.
An informal assessment is a conversation or brief written summary that helps you understand a tree's condition and your options. It is useful for deciding whether to pursue removal, whether a tree is worth saving, or what the general situation looks like. Many arborists provide informal assessments as part of a quote visit.
A formal arborist report is the structured document submitted to a municipality with a permit application. It has a defined scope, specific required content, and must be signed by an ISA certified arborist with their certification number. You cannot substitute an informal conversation for a formal report when applying for a permit.
When you contact an arborist and say you need a report for a permit, be specific about which municipality and which permit type. This ensures they scope and price the report correctly from the outset rather than delivering something that needs to be revised before submission.
What is an arborist report in Ontario?
A formal written tree assessment prepared and signed by an ISA certified arborist, covering the tree's species, size, health, structural condition and any risk factors. Required by Ontario municipalities for tree removal permit applications.
When do you need an arborist report in Ontario?
When applying for a tree removal permit, when construction activity will affect protected trees, when documenting hazard for insurance or legal purposes, or when a municipality requires tree documentation as part of a planning application.
Who can write an arborist report in Ontario?
Only an ISA certified arborist. Reports from uncertified individuals are not accepted by GTA municipalities. Ask for their ISA certification number and verify it is active before hiring.
What is the difference between an arborist report and a tree preservation plan?
An arborist report assesses a tree's condition and recommends removal or management. A tree preservation plan (TAPP or TPP) goes further: it specifies how trees will be protected during construction, including fencing, sequencing and monitoring. A preservation plan typically includes an arborist report as its foundation.
How much does an arborist report cost in Ontario?
Between $400 and $800 for a standard residential single-tree permit report in the GTA. Construction site reports and multi-tree assessments cost more. See our full arborist report cost guide for a detailed breakdown.
How long is an arborist report valid in Ontario?
Most GTA municipalities treat a report as valid for one to two years, provided the tree's condition has not changed. A report more than two years old, or from before a significant weather event, typically needs to be refreshed before a permit application is accepted.
Can an arborist report recommend against removing a tree?
Absolutely. A legitimate arborist report presents an honest assessment. If a tree is healthy and the concerns can be managed through pruning, a qualified arborist will say so. A report that always recommends removal regardless of condition is a red flag worth investigating.
We prepare ISA-standard arborist reports accepted by Toronto, Mississauga, Markham, Richmond Hill and other GTA municipalities. Call or email to get started.