Awaiting expert review. This page covers safety or regulatory rules that change over time. It is kept out of search results until a qualified reviewer has checked it; the sources below are dated so you can verify each point.
Quick answer
A tree risk assessment is a structured inspection in which a trained arborist judges how likely a tree, or part of it, is to fail, what it could hit if it does, and how serious the harm would be, then recommends ways to lower that risk.
A tree is only a hazard when something of value sits where it could land. The assessment is a professional judgment made on a set date, not a guarantee that a tree will stand.
Quick facts
The key facts about Tree Risk Assessment, with sources:
- Three parts of risk
- Potential for failure, local conditions that add to it, and a target that could be harmed 4
- Who is trained
- Arborists who complete the ISA Tree Risk Assessment Qualification (TRAQ), a voluntary credential 12
- TRAQ renewal
- Holders retrain and retest every seven years 1
- Reference method
- ISA Best Management Practices: Tree Risk Assessment 1
- Owner duty
- ISA says it is a tree owner’s responsibility to ensure the safety of others around trees on the property 3
- Power lines
- Never remove branches from or near power lines; call the electricity provider 3
Key takeaways
- A tree is a risk only when failure and a target meet. A leaning tree in an empty field is a different case from the same tree over a bedroom.
- ISA describes three levels: a quick limited-visual screen, a basic walk-around inspection and an advanced test of one suspected defect.
- Look for the signs, but let a qualified arborist judge how serious they are. ISA says evaluating seriousness is best done by a professional arborist.
- The TRAQ credential is voluntary and renewed every seven years. Ask for it by name when you book an assessment.
- Never prune, climb or cut near power lines. Call the electricity provider.
Risk is a defect plus a target, not a scary-looking tree
ISA’s homeowner brochure begins with a plain fact. There is no such thing as a completely safe tree. All trees can fall, but only a small number actually hit something or someone 3. A risk assessment sorts out which trees deserve attention.
Auburn University’s extension forester breaks risk into three parts. The first is the potential for failure, meaning the chance that the tree or a part such as a branch breaks or falls.
The second is environmental factors, the growing conditions that could add to failure. The third is a target, a person or object that could be harmed. Auburn’s bulletin states that without a potential target, a tree cannot qualify as a hazard 4.
That framing is why two similar trees can get different ratings. A dead limb over a quiet back corner is not the same job as the same limb over a play area.
The assessor also looks at how big the part is and how far it could drop, because ISA says the risk from a dead branch depends on its size and its distance from any potential targets 3.
The professional method behind this is ISA’s Best Management Practices: Tree Risk Assessment. ISA’s TRAQ page names it as the reference for the qualification, and it describes a Basic Tree Risk Assessment Form that builds on it 1. The form is the paper trail you can ask for after a visit.
How an assessment runs, from first look to report
The details vary by arborist and by level. The order below follows the three-part idea from Auburn and ISA.
- Name the targets. The arborist notes what sits within reach of the tree, such as a house, a driveway, a play area or a utility line 4.
- Choose the level. A screen, a full walk-around or a test of one defect, as described in the table below 4.
- Inspect the parts. A basic assessment covers the trunk, roots, branches, crown and site, and Auburn says arborists may use tools such as a clinometer and a decay probe 4.
- Look at the site and history. ISA’s checklist asks about construction, changes in soil level, topping and heavy pruning, because human activity can cause wounds, root loss and decay 3.
- Rate and recommend. The arborist suggests options. ISA lists pruning defective branches, cabling and bracing, routine care or removal 3.
- You decide. ISA’s credentials page says the training prepares arborists to give information to tree owners and risk managers who make the decisions 2.
- Spot a signCrack, lean, decay, dead limb
- Name the targetHouse, play area, lines, car
- Pick the levelScreen, basic or advanced
- Qualified arborist ratesDefect, conditions, target
- Owner choosesPrune, support, monitor or remove
The sequence combines Auburn Extension’s three parts of risk with ISA’s management options. Source: [4] [3]
The three levels of assessment, side by side
| Level | What it is | Typical tools or view | Best used for |
|---|---|---|---|
| Level 1: limited visual | A quick inspection on foot, from a vehicle or by drone, viewing one side of the tree 4 | Eyes only; often used to screen municipal trees 4 | Spotting obvious problems across many trees |
| Level 2: basic | A comprehensive inspection of the trunk, roots, branches, crown and site by a certified arborist 4 | Clinometer and decay probe 4 | Most single-tree questions from owners |
| Level 3: advanced | A detailed, costlier analysis that needs the client’s approval 4 | Sonic tomography, load and stability analysis, root excavation 4 | High-value trees or a defect Level 2 could not settle |
Level 1
- One side of the tree
- Fast and broad
- Flags obvious defects
Level 2
- Trunk, roots, branches, crown and site
- Hand tools such as a probe
- The usual starting point for an owner
Level 3
- One suspected problem
- Specialist methods
- Needs client approval
Source: [4]
A drive-by is a screen, not a clearance
Auburn describes Level 1 as a view of one side of the tree. A quick look can flag trouble. It cannot show that the unseen side, the roots or the inside of the trunk are sound.
Example: the same defect on three sites
The three cases are invented to show how a target changes the rating. The three-part structure is Auburn’s 4. The actions are examples, not ratings, and a qualified arborist makes the call on a real tree.
| Site (example) | Defect | Target within reach | How the three parts read |
|---|---|---|---|
| A: back corner of a large lot | Dead limb over 2 in. wide | None; fence only | Failure is possible, but no person or valuable object is within reach. A tree can only be a hazard if a target exists 4. |
| B: same tree, patio table below | Same dead limb | People sit under it | Same failure potential, but now a target is present. ISA says risk from a dead branch depends on its size and its distance from targets 3. |
| C: lean with a soil mound at the base | Exposed roots and heaved soil | Garage within reach | Clemson says exposed roots or a soil mound with a lean may signal an imminent hazard needing immediate action 5. Keep people away and call a qualified arborist. |
The point of the table is the last column. Defect alone does not set the urgency, and neither does a target alone. The pair does, so describe both when you call an arborist.
Where tree risk assessments show up
After a storm or a cracked limb. This is the most common trigger. ISA’s checklist includes questions such as whether branches have fallen and whether the trunk has cracks or splits 3.
Before construction, a patio or a grade change. ISA’s checklist asks whether the area has been altered by construction, changes in soil level, or new lawns or pavement. Our critical root zone page covers how far roots reach.
On a tree service bid. A bid to remove or prune a tree often rests on an informal risk judgment. If a bid says a tree is dangerous, ask which level of assessment was done and by whom. Read how to compare landscaping estimates before you sign.
Before a sale or in a dispute. A written assessment can document a tree’s condition on a given date. We found no source that sets how long one stays valid, so ask the assessor how long they stand behind the findings.
During a regular tree-care visit. ISA notes that regular tree care by a certified arborist gives a chance to spot defects and unacceptable risk levels 3.
What an assessment gives you, and what it cannot
What it can do
- Turns a vague worry into named defects, named targets and options 43.
- Can show that a tree with an ugly but minor defect needs only routine care, which ISA lists as one option 3.
- Gives a record that you acted. ISA says it is the tree owner’s responsibility to ensure the safety of others around trees on the property 3.
- Points to the right next step, from pruning to support to removal 3.
What it cannot do
- It cannot promise a tree will stand. ISA says all trees have the potential to fall 3.
- A Level 1 screen sees one side of the tree and cannot clear it 4.
- It does not carry out the work. Pruning, cabling or removal are separate jobs.
- Hidden decay may need Level 3 methods to confirm, and those are costlier and need approval 4.
Limits of the method, and what we could not confirm
Assessment is judgment, not measurement. Auburn’s bulletin describes failure potential in plain terms and ties it to the tree, the environment and any target 4. Two qualified arborists can look at the same tree and weigh a defect differently, which is a reason to ask for a second opinion on a costly removal.
Rules of thumb vary by source. Maryland Extension gives several percentages for when damage may be survivable and when removal is probably warranted 6. Other publishers give different figures or none. We show Maryland’s numbers in the chart below as one publisher’s guide, not a national rule.
We did not find a source for a standard valid-for period on an assessment, so we give none. ISA says credential holders retrain every seven years, but that applies to the arborist, not to the report 1.
We also did not read the Best Management Practices document itself. Level descriptions here come from ISA’s TRAQ page and from Auburn Extension’s summary. Ask your arborist which edition of the method they follow.
What drives the price of an assessment, and how long it stays useful
We publish no prices. What changes a quote is the level, the number and size of trees, the access around them, and whether you want a written report.
Auburn says Level 3 work is a detailed, costlier analysis that requires the client’s approval and is typically used for high-value trees 4. A Level 2 visit is the usual starting point for a single tree.
Some arborists fold a Level 2 look into a pruning or removal visit. Others charge for the consultation separately. Ask how the visit is billed before it happens, and ask whether the written form is included.
How long the findings stay useful depends on the tree and the site. Clemson Extension notes that risk rises as trees age, so owners should inspect them regularly 5. ISA ties risk to changes such as new construction or storm damage 3. We give no number of years.
For removal and pruning costs, use the tree removal cost tool and the cost hub. Both explain what sets a bid, not a flat figure.
Who does it and what you do before and after
You can look at a tree yourself. The assessment is for a trained arborist. UMD Extension says most tree pruning and removal jobs are not safe for the average person 6.
- Walk around the tree from the ground. Use ISA’s checklist of questions as your guide 3.
- Write down what you saw, with photos, and what sits near the tree.
- Find a credentialed arborist. ISA offers a Find an Arborist tool and a Verify a Credential tool on TreesAreGood.org 3.
- Ask for a TRAQ-qualified arborist. Clemson Extension recommends one who holds ISA credentials and the Tree Risk Assessment Qualification 5.
- Ask which level they will do and whether you will get a written form 41.
- If the plan includes root excavation or digging, a utility locate comes first. Call 811 two working days ahead 7.
- Pick a mitigation with the arborist, and get any work quoted by a qualified crew. Our guide to choosing a landscaping company covers questions to ask.
Stay clear of power lines and damaged trees
ISA says never to attempt to remove branches or any tree part from or near power lines, and never to go near downed power lines. If tree parts touch utility lines, call the electricity provider 3. Do not climb or use a chainsaw on a damaged tree. Leave that to a qualified arborist.
Keeping risk low between assessments
The are habits, not dates. Clemson Extension suggests a seven-point owner check that takes under 30 minutes and is done twice a year 5.
- Look up and down. Check for dead or hanging branches, cracks, cavities, mushrooms at the base and soil movement near the trunk 53.
- Keep the roots safe. Construction, soil level changes and compaction cause root loss and decay 3. See soil compaction for how packed soil hurts roots.
- Prune with a plan. Clemson says topped or hat-racked trees are more vulnerable to storm damage 5. Read tree pruning for correct cuts.
- Give routine care. ISA says mature trees need water, nutrients in some cases, mulch and pruning as their structure and the season dictate 3.
- Re-check after storms. A new crack, lean or fallen branch is a reason to look again.
Warning signs, and when to call right away
The are signs, not diagnoses. The sources below print them; a qualified arborist judges how serious they are.
- Dead, hanging or broken branches. Clemson says branches over 2 inches can cause damage and should be removed promptly by a professional 5.
- A lean with exposed roots or a soil mound. Clemson says such a tree may be an imminent hazard needing immediate action 5. Auburn calls a rapidly worsening lean a signal of possible imminent failure 4.
- Cracks that go into the wood. Clemson says if a crack extends beyond the bark into the wood, have an arborist inspect it 5.
- Weak unions and codominant stems. Auburn lists V-shaped unions with included bark and two stems of similar size from one point 4. Clemson says a crack where a branch over 3 inches joins the trunk signals a high chance of failure 5.
- Decay. Clemson says mushrooms or conks indicate advanced decay and a high probability of failure 5. Auburn adds visible cavities and sap leaking through bark 4.
- Root trouble. ISA lists cracks or separations in the soil as a warning, especially if the tree leans 3.
A sudden change is an emergency
UMD Extension says a sudden lean suggests root breakage or weakening and may call for immediate removal 6. Stay out from under the tree and call a credentialed arborist. If any part touches a power line, call the electricity provider and keep away.
After a major failure or when a tree has already moved, keep people and cars away from its drop zone until a qualified arborist has looked at it.
Standards, credentials and local rules
A standard, not a law. ISA’s Best Management Practices: Tree Risk Assessment is the reference for the TRAQ qualification, and TRAQ itself is described by ISA as a voluntary qualification 12. No federal rule requires a homeowner to hire a TRAQ holder.
Credential rules. To qualify, candidates take a two-day course and a half-day of assessments, then pass a written assessment and a performance-based one. Holders retrain and retest every seven years 1.
ISA’s credentials page says eligibility is open to holders of credentials such as ISA Certified Arborist and ISA Board Certified Master Arborist 2.
Licensing. Maryland Extension recommends a Maryland-licensed tree expert or a certified arborist for pruning and removal jobs 6. Licensing differs by state, so check yours.
Permits. A tree flagged as risky may still need a permit to remove. Many cities protect large or heritage trees. See our tree removal permit rules research.
Liability. ISA says a tree owner is responsible for the safety of others around trees on the property 3. How that works in law differs by state, and we do not give legal advice.
Tree risk assessment compared with related terms
| Term | What it answers | Who usually acts | Main difference |
|---|---|---|---|
| Tree risk assessment | How likely is failure, what is the target, how bad is the harm? 4 | Qualified arborist 1 | A judgment that leads to options |
| Tree cabling and bracing | Can weak parts be supported? | Certified arborist 3 | One possible response, not a rating |
| Crown thinning and reduction | How can weight or height be cut? | Arborist or tree crew | A pruning method, not an assessment |
| Transplant shock | Why is a newly planted tree struggling? | Owner with extension advice | Health problem, not structural risk |
| Tree removal | How is the tree taken down? | Qualified crew | The result of a rating, with costs and permits |
Common beliefs about hazardous trees
- Myth A healthy-looking crown means the tree is safe.
- Reality Auburn lists defects in the roots, unions and wood that do not show in the crown, and ISA says evaluating the seriousness of defects is best done by a professional arborist 43.
- Myth Mushrooms at the base are harmless.
- Reality Clemson says mushrooms or conks indicate advanced decay and a high probability of failure 5. ISA also lists mushrooms at the base as a checklist item 3.
- Myth Cables and braces make a tree safe.
- Reality ISA says such supports are not guarantees against failure 3. The cabling page explains the limits.
- Myth A tree is a hazard because it is big.
- Reality Auburn says that without a potential target a tree cannot qualify as a hazard 4.
The regional variable: pests that make trees brittle
One regional fact changes a risk judgment. In places where emerald ash borer has killed ash trees, Maryland Extension says the dead wood becomes very brittle and limb breakage is a major risk 6.
Storm patterns, soil type and local permit rules also vary by region. Ask a local credentialed arborist what is common near you, and read our tree removal permit research before you plan any removal.
When to get an assessment, and your next step
Get a Level 2 assessment when a tree has a defect from the list above and something of value sits within reach. Get it sooner if the tree has moved, cracked or lost a large limb. If you are only curious, the owner check in the maintenance section is a good first step.
Your next step is to write down the tree’s signs and what lies beneath it, then verify a credentialed arborist and ask for a TRAQ-qualified one. Compare the plan to the tree service page so you know what each job includes.
If the arborist suggests removal, ask which defect and which target drove that advice, and what the alternatives are. A second opinion is reasonable when the work is large.
Questions about Tree Risk Assessment
What is a tree risk assessment?
It is a structured inspection by a trained arborist who judges how likely a tree or part of it is to fail, what it could hit and how serious the harm would be.
Auburn Extension says a tree cannot qualify as a hazard without a potential target. The result is a set of options, not a guarantee.
What are the levels of tree risk assessment?
ISA’s method has three levels. Level 1 is a limited visual look, often one side of the tree on foot, from a vehicle or by drone.
Level 2 is a basic inspection of trunk, roots, branches, crown and site. Level 3 is an advanced method such as sonic tomography or root excavation, and it needs client approval.
What does TRAQ mean?
TRAQ stands for ISA Tree Risk Assessment Qualification. ISA describes it as a voluntary qualification for arborists. Candidates take a two-day course, then pass a written and a performance-based assessment, and they retrain and retest every seven years. It shows training in limited-visual and basic assessment and the principles of advanced methods.
How do I know if my tree is dangerous?
Look for dead or hanging branches, cracks into the wood, mushrooms or conks, cavities, a lean with exposed roots or a soil mound, and weak unions. Then ask whether anything of value sits within reach. These signs are reasons to call a credentialed arborist, not a final diagnosis.
Is a leaning tree always about to fall?
No. Sources describe lean as a warning sign that depends on the rest of the tree. Clemson says a lean with exposed roots or a soil mound may be an imminent hazard.
Auburn points to a rapidly worsening lean as a signal of possible imminent failure. A long-standing lean with sound roots may be fine, so have it checked.
Who is responsible for a tree on my property?
ISA says it is the tree owner’s responsibility to ensure the safety of others around trees on the property. How liability works in law differs by state, so we cannot say more here. A written assessment from a credentialed arborist is one way to show you looked into a concern.
Can I remove a hazardous tree myself?
It is not advised. Maryland Extension says most pruning and removal jobs are not safe for the average person and recommends a licensed tree expert or certified arborist. Work near power lines should always be done by a professional. Check local permit rules before any removal.
What should I do if a tree touches a power line?
Keep away and call the electricity provider. ISA says never to attempt to remove branches or any tree part from or near power lines, and never to go near downed lines, because they could still be conducting electricity. Do not climb or cut anything in contact with a line.
Does a risk assessment mean the tree has to come down?
No. ISA lists several options an arborist may suggest: prune defective branches, cable and brace, routine care, or removal. Removal is for trees with unacceptable risk. The assessment names the defect and target so you can pick the least drastic option that works.
How often should a tree be checked?
Sources give no single schedule. Clemson Extension suggests an owner check of under 30 minutes twice a year, and says risk rises as trees age. ISA says regular care by a certified arborist helps spot defects. Look again after storms, construction or any new crack or lean.
Sources
- International Society of Arboriculture, TRAQ (Tree Risk Assessment Qualification), retrieved .
- International Society of Arboriculture, ISA Tree Risk Assessment Qualification (credential page), retrieved .
- ISA, Recognizing Tree Risk (TreesAreGood.org brochure, v02.2021; PDF text extracted locally), retrieved .
- Auburn University / Alabama Extension, Spotting Danger: How to Identify and Assess Hazard Trees (FOR-2175, April 2025), retrieved .
- Clemson Cooperative Extension HGIC, A routine check-up of trees saves lives and property (June 2021), retrieved .
- University of Maryland Extension, How Do You Decide When to Remove a Tree?, retrieved .
- USA North 811, DIYers (call 811 before you dig), retrieved .
Expert review
Written by the HyreYard Research Desk. Not yet reviewed by an outside expert. We say so rather than imply a review that has not happened; see our editorial policy.
How the numbers were checked: Level descriptions are Auburn Extension’s summary of the ISA method. Credential facts are from ISA’s TRAQ and credentials pages. Warning signs come from ISA’s brochure (text extracted from the PDF), Clemson, Auburn and Maryland Extension.
Percentages in the chart are Maryland Extension’s rules of thumb. We did not read the Best Management Practices document or the ANSI standard. Held under G-REV until a credentialed arborist reviews the page.
Suggest a correction. We fix errors and say what changed.