Key takeaways
- The critical root zone is the part of the root system a tree needs to stay healthy and stable, and it can reach well past the branch spread.
- Fence the tree protection zone before the first machine arrives, with signs that say why and who to call.
- Compaction, grade changes, trenching, spills and trunk wounds are the five common ways construction injures a tree.
- Bring the arborist in during design, because small plan changes save more trees than fixes made later.
Most trees lost to building are not cut down by the crew. They are slowly starved or crushed by it. The ISA puts it bluntly: small injuries that accumulate can start a decline that is hard to reverse.
How does construction hurt a tree?
The ISA lists the main ways. Grading, trenching, paving, changed drainage and added or removed soil within the root zone damage roots. Heavy equipment compacts the soil, which slows root growth, limits water getting in and reduces the oxygen roots need. Machinery can tear bark and wound the trunk and root collar. Heat from running machines and burning material can damage bark and leaves, and spilled fuel or concrete washout can change the soil chemistry.
Removing trees can hurt the ones left behind. The ISA notes that closely spaced trees support each other, and exposing the survivors can lead to sunscald or structural failure.
What is the critical root zone and the tree protection zone?
The critical root zone is the portion of the roots essential to health and stability, and a tree's root zone can extend far past its outer branches. The ISA says an ISA Certified Arborist should define the tree protection zone early, with specific limits on construction activity inside it.
Our glossary entries on the critical root zone, the drip line and the structural root zone explain the terms.
What should happen before, during and after the build?
Before: the ISA says an arborist can recommend where protection fences go, with signs attached to say why people should stay out and who to contact. If machinery must come near a trunk, extra trunk protection can be recommended. Where trenching or grading will damage roots, an arborist can prune the roots out of the way or cut them cleanly before the damage is done, and may plan temporary irrigation when root loss is significant.
During: the zone needs regular monitoring by an arborist. After: new plantings, irrigation, lighting and planting soil near existing trees can hurt them, and a post-construction maintenance plan helps trees recover.
- Walk the site with the arborist before design is final.
- Mark the protection zone and fence it before equipment arrives.
- Keep parking, storage, fill and washout outside the fence.
- Have the arborist visit during the build, not just at the start.
- Plan watering and aftercare when roots have been lost.
Which rules apply in our area?
In Reno, the city's tree protection ordinance addresses preservation, replacement, mitigation plans, prohibited activities next to trees and permitted construction methods, and anyone working within 10 feet of a publicly owned tree must contact the City's Urban Forester before digging, according to the Truckee Meadows Water Authority. Around Lake Tahoe, trees permitted for removal as part of a development project do not need a separate TRPA removal permit, though the project itself does.
See permits in Northern Nevada and the Tahoe 14-inch rule. The agency decides.
How can we help a build?
We do lot clearing, tree removal, crane work and arborist consultation for builders and land owners. A certified arborist assesses the trees before work starts. See lot clearing for builders and land owners and call 775.232.8243 for a free estimate.
Sources
- International Society of Arboriculture, Trees Are Good: Avoiding Tree Damage During Construction (brochure) (read October 17, 2026)
- Truckee Meadows Water Authority: Local Tree Ordinances (read October 17, 2026)
- Tahoe Regional Planning Agency: Trees and Defensible Space (read October 17, 2026)