If someone has told you a tree on your property is a hazard, or you have a suspicion of your own, a hazard tree assessment is how that gets settled with evidence instead of opinion. It is a structured evaluation that produces a documented answer about whether a tree presents unacceptable risk and what to do about it.
Risk is three things, not one
The core idea is that a defective tree is not automatically a risky tree. Professional tree risk assessment considers three factors together:
- Likelihood of failure. How probable is it that this tree, or this part of it, breaks or falls?
- Likelihood of impact. If it did fail, would it actually hit anything? A tree that would drop into an empty field is a different proposition from an identical tree over a bedroom.
- Consequence of impact. How bad would that be? A limb on a shed is not a limb on an occupied structure.
This is why two identical trees can get opposite recommendations. A hollow trunk in the middle of a back acre may be fine to keep, and even valuable as wildlife habitat. The same trunk beside a driveway where the kids get picked up is not.
What the arborist does on site
Starts with context. What is around the tree, what is under it, how often are people there, and has anything changed recently — construction, grading, trenching, a driveway installed over the root zone. Root damage from work done two or three years ago is a frequent cause of decline that shows up much later.
Examines the root zone and trunk flare. The base tells you the most. Soil cracking or heaving, exposed or severed roots, fungal fruiting bodies at the flare, girdling roots, or a trunk that enters the ground like a telephone pole rather than flaring outward — that last one can indicate buried root problems.
Works up the trunk. Cracks, cavities, old wounds, conks, unusual swelling, missing bark, insect activity. Where decay is suspected, a mallet sounding can reveal hollow areas by pitch, and where more information is needed, instruments can measure resistance through the wood.
Assesses the canopy and unions. Deadwood and where it sits, the ratio of live to dead limbs, codominant stems with included bark, previous topping cuts and the weak regrowth they produce, and whether the crown is balanced or loaded heavily to one side.
Considers species and site. Douglas fir, western red cedar, and big leaf maple each fail in characteristic ways. A recently exposed tree — one that lost its neighbors to a clearing project — is at elevated risk because it grew up sheltered and has not developed wind-firmness.
What you should get at the end
A useful assessment produces a written report, not a verbal impression. It should include what was inspected, what was found, a risk rating, and specific recommendations with timeframes.
Recommendations are rarely just remove or do nothing. The realistic range includes pruning to remove deadwood or reduce end weight, crown reduction to lower the load on a weak stem, cabling or bracing to support a union worth keeping, moving the target rather than the tree, scheduled re-inspection, or removal where risk genuinely cannot be brought down to acceptable.
When it is worth paying for one
- A large tree within striking distance of your house and you have concerns
- A neighbor has raised a concern, or you need to raise one, and you want documentation
- You are buying property with significant mature trees
- Construction is planned near a tree you want to keep
- A storm has been through and you want to know what is still sound
- A tree company has recommended removal and you want a second opinion from someone not selling the removal
That last one comes up more than you would expect, and it is a completely reasonable thing to ask for.
Who should do it
Look for an ISA Certified Arborist. The additional TRAQ qualification — Tree Risk Assessment Qualified — indicates specific training in this exact methodology. Ask for it by name.
Cutting a tree down and knowing whether it needs to come down are two different skills. Plenty of capable crews have the first and not the second.
Cascade Tree Works serves Vancouver, Battle Ground, Camas, Brush Prairie, La Center, Washougal, Ridgefield, and Hockinson. Our ISA Certified Arborists can look at your tree and tell you plainly what it needs. Request a residential estimate.
