# calculating tree protection zone



## dw3000 (Dec 4, 2011)

Hi,

Can anyone tell me the standard tree protection zone/critical root zone?

In some places I have read that as a general rule it should be 1 ft diameter per inch of trunk diameter (ISA study guide). Other sources recommend 1 ft radius per inch of trunk diameter. Which is it?

Thanks.


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## beastmaster (Dec 4, 2011)

It radius. I'm sure there are many formulas, but a radius of 1.25 feet for each inch of trunk is a good ball park figure.

Mature Tree Protection Zone Radius
Trunk Diameter Good Better best Protection
8 inches 10 feet 12 feet 20 feet
12 inches 15 feet 18 feet 30 feet
16 inches 20 feet 24 feet 40 feet
20 inches 25 feet 30 feet 50 feet


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## dw3000 (Dec 4, 2011)

Thanks. That makes sense. Although, if this question appears on the certification exam, perhaps I should go with what the study guide says.


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## beastmaster (Dec 4, 2011)

http://www.mfc.ms.gov/pdf/Pubs/tree_protection.pdf

This is a ISA booklet I think. It's been a long time ago sense I took the test, but of course go with what is in the work book. Just be sure. The test isn't hard but they do try and twist the questions some, so be sure of your facts.


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## sgreanbeans (Dec 5, 2011)

Are you asking for the test or are you actually setting one up?


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## dw3000 (Dec 5, 2011)

I was asking for the test. In practice, I would probably go with the radius, if practical, since bigger is usually better. Took the test today and passed. Thanks, Beastmaster, for the link.


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## PJM (Dec 6, 2011)

Congrats dw !!


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## ClimbMIT (Dec 8, 2011)

Awesome! I just took my State test last week and waiting on the results! I am about 95% sure I passed. This test was hand written:Old School I will take the ISA when I have the funds aside.


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## herby57 (Dec 22, 2011)

Another way, as practiced in Germany:
Crown projection (means outer branches, projected to the ground) plus 6' in radius - no much calculating and you left root area untouched.


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