Read This Before You Build Near a Big Oak in Austin
Your backyard has one huge live oak, and the obvious spot for a patio is right under its shade. In Austin that tree may be protected, and so is the ground around its roots.
In Austin a tree 19 inches or more across is protected, and a heritage tree is 24 inches or more of listed species, including all oaks. Work in their root zones has tight limits and often needs a tree review.
- Trees under 19 inches are not regulated on house lots.
- Protected and heritage trees need a permit to remove or impact.
- The inner quarter of the root zone allows no impact.
- Half the full root zone has to stay untouched.
Which Trees Are Covered
The City Arborist page sets the sizes. Diameter is measured 4.5 feet above the ground. A protected tree is 19 inches or more. A heritage tree is 24 inches or more and one of the listed species, which include all oaks, pecan, cedar elm and bald cypress.
The Root Zone Limits
The city rules for trees on residential property work in rings around the trunk.
- Inner quarter of the root zone. No impact at all.
- Inner half. No cut or fill deeper than 4 inches.
- Full root zone. At least half must stay untouched.
What That Means for a Deck or Pergola
A deck or pergola on a few small footings disturbs far less ground than a solid floor, so it can often sit closer to a big tree. Footings still have to stay out of the inner quarter of the root zone, and digging in the inner half is capped at 4 inches of cut or fill.
When a Review Is Needed
A tree review application is needed to remove a regulated tree, prune 25 percent or more of its canopy, or start work that may disturb its critical root zone. On a project with a building permit, the tree review runs with the plan review.
The Gaps
Most backyard advice only warns about roots heaving a deck later. In Austin the bigger issue comes first, because the city limits the digging itself. Oaks also bring oak wilt timing into the schedule.
Answers in a Sentence
What size tree is protected in Austin?
19 inches or more in diameter, measured 4.5 feet above the ground.
Are all oaks heritage trees in Austin?
Oaks 24 inches or more across are heritage trees.
Can a patio go under a protected tree?
Usually not in the inner half of its root zone, where cut or fill is capped at 4 inches.
Where We Got This
- City Arborist (Tree Reviews and Permitting), City of Austin Development Services Department
- Trees on Residential Property, City of Austin Development Services Department
Elsewhere on the Site
Where to Find Deck and Patio of Austin
706 W Ben White Blvd A, Austin, TX 78704
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