Arborist report: what it is, what’s in it, and when WA and OR cities require one

What is an arborist report?

Kirkland’s code has the plainest definition: an arborist report is the “written review and recommendations” of a qualified professional arborist, submitted to meet the city’s tree rules (KZC 95.10). Who writes them, how to check credentials and how assessments are billed are covered on the arborist hub for Washington and Oregon; this page is about the document itself.

A report is evidence, not a permit. Seattle, for instance, approves a hazard-tree removal only when the tree poses a high risk to people or property, and the arborist’s assessment is how an owner shows that. Most of the reports in the city rules below are tree risk assessments, so it helps to know how ISA’s tree risk assessment levels and ratings work before you order one.

Types of arborist reports and what each contains

“Arborist report” covers several documents. They share a format (the tree, its condition, the finding, the credential) but answer different questions.

Sources: Seattle SDCI Tip 242B; Kirkland KZC 95.25; Lake Oswego LOC 55.02.042; Portland PCC 11.50.070; Bellevue LUC 20.20.900 and tree removal page; ISA TreesAreGood brochures on construction damage and tree values. Checked 2026-10-02.

Tree protection plans start early. ISA advises bringing an ISA Certified Arborist onto a construction project at the planning stage to define a tree protection zone, because grading, trenching and compaction damage roots and the decline can take years to show. Appraisals start late, after the loss: ISA notes that the valuation guidelines are recognized by insurers, courts and in some cases the IRS, and that the appraisal should be made as soon as possible after the damage.

Appraisals carry the most weight when someone else did the cutting. Both states allow treble damages when trees on another person’s land are cut or injured without lawful authority (RCW 64.12.030; ORS 105.810). The state rules are on Washington neighbor tree law and Oregon neighbor tree law.

When WA and OR cities require an arborist report

This is general information, not legal advice. The rules below are paraphrased from each city’s code or permit page as we read them on October 2, 2026; codes change, so confirm with the city before you file.

Source: each city’s code or permit page, linked under Sources, checked 2026-10-02. Paraphrased; not legal advice.

Two patterns stand out. Seattle, Bellevue, Kirkland and Shoreline lean on TRAQ for hazard paperwork, and Bellevue and Kirkland let a documented hazard tree skip the usual annual limits, though both still want a permit for it. In Portland and Lake Oswego the city makes the call on a dead or dangerous tree, and an arborist’s report is the most direct evidence an owner can offer; Lake Oswego can require one. Thresholds for other cities are in Washington tree removal permits, Oregon tree removal permits and the tree permit checker, and the city pages for Seattle arborists and Portland arborists go deeper on those two codes.

Who can write an arborist report?

For a hazard report, the common thread is TRAQ. Seattle requires it on the risk form, Bellevue’s hazardous-tree definition needs the written opinion of a qualified tree professional who also holds TRAQ, Kirkland requires TRAQ or an equivalent for anyone assessing a hazard tree, Lake Oswego names a Tree Risk Assessor Qualified Arborist, and Shoreline uses a TRAQ arborist for hazard trees in critical areas. TRAQ is an ISA qualification for people who already hold an ISA credential or a related degree, and it is valid for seven years.

For other reports, cities accept a wider list. Portland’s code counts an ISA Certified Arborist or an ASCA registered consulting arborist; Bellevue adds ISA’s municipal specialist and Board Certified Master Arborist and the SAF certified forester; Kirkland asks for two or more credentials, and for tree retention during development, at least three years’ experience protecting trees during construction. Seattle adds a business test: the report’s author must be on SDCI’s Tree Service Provider directory or on retainer with a registered provider. What each credential means is in what an arborist does.

Tip: if the company writing the report will also bid the removal, ask whether it would recommend the same thing if it were not doing the work. A consulting arborist who does not cut trees is the other option when the stakes are high.

What a tree risk assessment report should include

Seattle’s tip spells out the content: the overall health of the tree, an analysis of potential targets, the factors behind the need for removal, and the tree’s dimensions and structure, filed with photos and a site plan. Kirkland adds that the report must explain how the tree meets the city’s hazard definition and give an overall risk rating with matching mitigation measures, using the TRAQ method. Lake Oswego asks for alternatives to removal.

When the report arrives, read it in this order:

How to get an arborist report for a permit

1. Check the city rule firstFind out whether your city wants a report at all, which form, and which credential. A healthy yard tree in Tigard needs neither; a hazard tree in Seattle needs both.
2. Hire the right credentialTRAQ for anything called a hazard. In Seattle, the assessor must also be with, or on retainer to, a registered Tree Service Provider. Verify the ISA number in ISA’s online credential directory, linked from TreesAreGood.org.
3. Say what the report is forName the city and the permit, and hand over any form the city names: the ISA risk assessment form Seattle and Shoreline ask for, or Redmond’s Hazard Tree Removal Declaration. Ask for photos and a site plan.
4. Get the price for the report on its ownAsk for the site visit and the written report as separate lines, and whether the fee changes if the tree needs a climbing inspection or instruments.
5. Read it before you fileRating, method, targets, options, credential, date. Ask for corrections before the city sees it.
6. File it and keep a copyAfter an emergency removal the clock is short: 10 calendar days in Seattle; 7 days in Portland, Kirkland and Lake Oswego.

None of the city pages we checked set an expiration date for a report or a turnaround time, so ask the city how recent a report must be if your permit could take months. What a visit and a written report typically involve, and how to compare offers, are on the arborist hub.

If the report confirms the tree has to come down, the permit and cost questions are in hazard tree removal, and modeled removal prices are on tree removal.