Is my tree dangerous? What a tree risk assessment is and when to get one

Updated November 10, 2026 · KeystoneProGuide editorial team

What is a tree risk assessment?

A professional judgement of how likely a tree, or part of it, is to fail, and what it would hit if it did. The U.S. Forest Service defines a hazard tree as one with a structural defect that makes it likely to fail in whole or in part. The International Society of Arboriculture (ISA) frames the question in terms of risk: trees provide large benefits, it says, but when they fall and injure people or damage property they become liabilities, and understanding the risk makes a property safer and can prolong the tree's life.

Who is qualified to do one?

Someone trained for it. ISA offers a Tree Risk Assessment Qualification, known as TRAQ, which Penn State Extension describes as a credential for Certified Arborists to learn to inspect trees for risk. ISA's consumer site lets you search for arborists who hold it. Penn State's advice for large trees around a home is to have a TRAQ-trained and qualified arborist conduct the assessment, and to have an ISA Certified Arborist evaluate the trees' structure and condition as a way of preventing storm damage.

What does the assessor look at?

Defects, the species and the targets. Penn State's guidance for tree inspectors lists what to look for: deadwood, cracks, decay, cavities, included bark and fungal fruiting structures. It says inspectors must understand how trees wall off decay, and that species differ, with sugar maple and oak doing it much better than silver maple and poplar. The Forest Service adds conks, broken tops, scars at the base, many downed limbs, ants and an abundance of woodpecker holes as signs of possible internal rot.

ISA says an inspection may be a simple visual one, or may use instruments to check for decay inside the wood.

The other half is what lies underneath: the house, the driveway, a play area, the street. ISA's first option for reducing risk is to move the target where that is possible, such as a picnic table or a parked car.

Why can't you judge it yourself?

Because appearances mislead. Penn State warns that a tree can look very healthy, with lots of green foliage, yet have major structural defects or fungus at its base. It also says to be careful with the words "unhealthy" and "diseased": a diseased tree may not be a high risk, while a healthy-looking tree may have internal decay, root rot or structural defects that could lead to failure. Some trees are obvious; Penn State calls a completely dead tree, or one full of deadwood, a "no-brainer". The rest need a trained eye. The signs you can watch for yourself are in signs a tree needs an arborist.

Should the assessor be the company that will do the work?

Penn State says not, at least for public trees. In its advice to municipal shade tree commissions, it says the arborist hired to assess risk "should not be the same arborist who will be bidding on the removal of the trees," to avoid any conflict of interest. Its advice to homeowners after storms is similar in spirit: a second opinion from another qualified arborist before removing a tree can be worthwhile. Paying separately for an assessment from someone who will not be quoting for the removal is one way to apply the same idea at home.

What should a written assessment say?

Penn State says inspections should always be documented in writing, whether or not a tree is found defective, and that the record should include the date, the inspector's name, the defects noticed and the recommended treatments. It mentions the Basic Tree Risk Assessment Form developed by ISA as one standard format. A report is also useful later. Doylestown Borough, for example, requires documentation and photographs from a certified arborist when a hazard tree has been removed in an emergency without a permit, and Philadelphia's zoning code lets a heritage tree on a development site be removed without a special exception, with replacement, when a certified arborist's report finds it dead, damaged or diseased enough to be a danger.

What can be done short of removal?

More than people expect. ISA lists the options an arborist familiar with risk assessment may suggest:

• Move the target, where it can be moved.
• Prune out the defective branches. Penn State says that sometimes pruning large deadwood is all that is needed.
• Cable and brace weak branches or stems. ISA says such supports are not guarantees against failure, and that installed hardware must be inspected regularly.
• Provide routine care, such as water, mulch and pruning.
• Remove the tree when the risk is unacceptable, and plant a replacement in a suitable place if possible.

What does an assessment cost?

The cost survey Angi puts an arborist consultation at $75 to $150, a written report covering several trees at $450 to $700, a basic tree inspection at $0 to $150 and cabling at $200 to $400. Other price ranges are in what tree work costs.

Does an assessment matter for insurance?

It can. The Pennsylvania Insurance Department says insurance policies may deny claims for damage caused by negligence, such as neglecting dead or overhanging limbs. Keep any written assessment, together with the receipts for the work it recommended. For hiring the arborist who does the work, see how to choose a tree service. Businesses that serve your area are on the tree services directory page.

Sources

1. Managing Hazards and Risk, International Society of Arboriculture (TreesAreGood.org)
2. Dealing with Tree Risk: Tips for Municipal Shade Tree Commissions, Penn State Extension
3. Helping Trees Recover After Storms, Penn State Extension
4. Hazard Trees, U.S. Forest Service
5. How Much Does an Arborist Cost?, Angi
6. Natural Disaster Insurance Guide, Pennsylvania Insurance Department
7. Chapter 25 Trees, Part 1: General Regulations, Borough of Doylestown
8. The Philadelphia Code, Section 14-705, Landscape and Trees, City of Philadelphia (The Philadelphia Code)