The method
How this tool reaches its answer
A tree is only a hazard if two things are true at once: something about it can fail, and something below it matters. A dead limb over an empty field is a mess. The same limb over the path your children walk every morning is a hazard. This wizard asks for both halves.
The structure follows the thinking behind the ISA Tree Risk Assessment Qualification: how likely is a failure, how likely is something to be underneath when it happens, and how bad would the consequence be. Answer honestly and the rating that comes back is conservative on purpose — a tool that tells a homeowner a leaning tree with heaving roots is fine is a tool that gets someone hurt.
Nothing here replaces a site visit. A visual assessment from the ground is the first tier of tree risk assessment and it is genuinely useful, but decay in the base of a pine cannot be seen or measured from the pavement. If this wizard says moderate or worse, book the walk-through.
How the rating is reached
Rates and bands last reviewed October 2026 · coastal San Luis Obispo County market rates
| Rating | What it means for you |
|---|---|
| Low | The tree looks sound and little or nothing is underneath. Re-inspect after a storm and keep the deadwood down. |
| Moderate | One or two defects, or a real target. Prune, deadwood, thin or cable to reduce the load. |
| High | A significant defect over something that matters. Treat soon, and keep people out from under it in the meantime. |
| Extreme | Failure appears likely or is already starting. Keep everyone clear and call us now. |
Before you answer each screen
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The base and the lean
- Soil lifting, cracking or tilting on the far side of a lean is a root plate coming out of the ground, and that is a failing tree.
- Mushrooms or conks at the base mean decay inside the trunk where you cannot see it, and they matter more than the crown looks.
- A lean the tree grew into is normal on a wind-shaped coast; a new lean is not, and the two are told apart by the soil rather than by the angle.
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The trunk
- A deep or opening seam is a structural defect in the wood that carries the load, and it can be invisible from ten feet away.
- A hollow covering a third of the trunk has removed a third of the wood; the tree may stand for years and then not.
- Conks are the fruiting body of decay, so what you can see above the bark is a fraction of what is inside it.
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The crown
- A tight V with bark trapped in the union is a fork that fails rather than bends, and it usually fails in a wet wind.
- Whole dead limbs high in the crown are the reason to keep people out from under the tree until they are taken out.
- Sudden dieback across most of a crown in a single season is a root or vascular problem rather than old age.
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What is underneath
- A dead limb over an empty field is a mess; the same limb over a driveway is a hazard, and the rating says so.
- Eucalyptus, willow and cottonwood drop limbs without warning, so the same defect scores higher in those species.
- A playground, a school route or a road raises the consequence far more than anything about the tree itself changes.
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Your risk rating
- The rating is likelihood of failure multiplied by likelihood of impact, the same shape an ISA risk assessment uses.
- This is a visual assessment from the ground: decay in the base of a pine cannot be measured from the pavement.
- A moderate rating or worse deserves a site visit rather than a wait, and an extreme one deserves it today.
What the tool cannot know
A browser cannot see a tree. Decay inside a trunk or a root plate, soil and drainage, hidden utilities, access and crane reach, permits, protected species and boundaries are confirmed on site or not at all — which is why every figure here is a range with its method beside it, and why the only price that binds anybody is a written one after a walk-through.