Be conscious of any trees that could get damaged when you start working on a new project.
The City of Austin preserves the natural resources that make Austin beautiful. To keep Austin gorgeous, the city protects large trees and their roots.
Protected tree sizes
Certain tree sizes are protected in Austin and require a special permit to cut them down. You will need a Tree Ordinance Review Application if your project:
- involves a tree of any species that is 19 inches or more in diameter (59.6904 inches around),
and requires you to:
- remove the tree,
- or do work near the critical root zone.
To calculate a tree’s diameter, measure the circumference of the tree from 4.5 feet above the ground (diameter at breast height or DBH), and divide by Pi (3.14). Trees smaller than 19 inches in diameter are not protected.
What is a critical root zone?
The ground surrounding a tree where water that drips down from canopy soaks into the roots. Learn more
Digging into critical root zones
A tree’s critical root zone depends on its size. Larger and older trees have bigger critical root zones that must be built around. Even if your completed project won’t be within 10 feet of a tree, bringing in construction equipment may affect its health. For example, a large cement truck driving on your property can damage a tree’s root system since it is just 4 inches underground.
How do I calculate the critical root zone?
The diameter of the tree’s trunk in inches equals the size of its critical root zone in feet. For example, a tree with a diameter of 20 inches has a critical root zone of 20 feet.
To understand where you can and can’t build around trees, imagine that there are three development impact zones around the base of the tree. We’re using a tree with a 20 inch diameter in the example below.
The Critical Root Zone
In this example, the critical root zone extends 20 feet from the base of the tree. You can dig into the ground in the outer half of the critical root zone (in this example: between 10 to 20 feet from the base of the tree or the green zone).
¼ Critical Root Zone
The ¼ critical root zone (in this example: the red zone) extends 5 feet (¼ of 20 feet) out from the base of the tree on the ground level. You will damage the tree’s roots if you dig in this zone.
½ Critical Root Zone
The ½ critical root zone (in this example: the yellow zone) lies between 5 and 10 feet from the base of the tree. You can only dig 4 inches into the soil in this zone.
You may not be able to remove heritage trees because they are highly protected by the City of Austin in order to preserve their natural beauty. Navigating the critical root zone of heritage trees may be difficult if the trees are 24 inches or more in diameter and one of the species on the list below.
- All Oaks
- Arizona Walnut
- American Elm
- Bald Cypress
- Bigtooth Maple
- Cedar Elm
- Eastern Black Walnut
- Texas Ash
- Texas Madrone
You may be able to apply for a variance to have the heritage tree removed if the heritage tree is dead or is a hazard to life or property.
Contact the city arborists about your project if you have a heritage tree in your yard.
What if my tree is a heritage species but not 24 inches in diameter?
Then it’s not big or old enough to be a heritage tree. If your tree is a heritage species and is between 19 and 24 inches in diameter, then it would fall under protected tree size regulations only.
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