Tree protection zone calculator
Most of a tree’s roots are in the top 12–18 inches of soil and spread well beyond the branches. Driving, stockpiling, trenching or changing the grade over them can kill a mature tree, often a few years later. Before any work, fence off a protection zone.
Measure the trunk at 4½ ft (1.4 m) above the ground. Wrap a tape around it for the circumference, or measure the diameter directly.
Why trees die after construction
Roots need air as much as water. Compaction from vehicles crushes the pore spaces; fill soil buries roots too deep; trenching cuts them. The tree may look fine for a season or two, using stored energy, then decline from the top down. By the time you see dieback, the damage was done years before.
The zone here scales with the trunk, the tree’s age and how well the species copes, following a widely used arborist approach. The simpler rule of thumb, one foot of radius per inch of trunk diameter, is shown in the working for comparison.