Most backyard ADU sites in Madison aren’t blank slates. There are trees — sometimes significant ones — and where those trees are located relative to where you want to build matters more than most homeowners expect. Madison has an urban forestry ordinance with real teeth, and it becomes part of the ADU permit process on any project where tree removal or root zone impact is involved.
Madison’s Urban Forestry Ordinance
Madison General Ordinance Chapter 8.34 governs tree removal on private property for trees over 5 inches diameter at breast height (DBH) when removal is associated with a development permit. Removing trees to make room for an ADU is subject to review — not something you can do unilaterally before permit submission. The city’s Urban Forestry Division reviews site plans as part of the standard interdepartmental site plan review process.
Street Trees Are Off-Limits
Trees in the public right-of-way — between the sidewalk and the street — are city property. You cannot remove a street tree without explicit city permission, which is rarely granted for an ADU project unless the tree poses an active safety hazard. If your project involves a new driveway or utility trench that would disturb the root zone of a street tree, the project must be designed around that constraint.
Protected and Heritage Trees
Madison maintains a register of notable and heritage trees. Removal of a heritage tree is essentially prohibited. Even non-heritage large trees (12+ inches DBH) receive more scrutiny. If removal is necessary, Urban Forestry will require a tree survey, typically an ISA-certified arborist’s report, and a mitigation plan including replacement planting.
How This Affects ADU Siting
The most common scenario: a homeowner has a large backyard tree roughly where they want to put the ADU. The tree can’t come out without Urban Forestry approval, and approval may come with conditions. On projects like this, we site the ADU to work with the tree — not against it. Setback from the trunk, root zone protection specifications for the foundation, and construction sequencing that minimizes soil compaction near tree roots are all addressed in the design and site plan phase.
We assess tree constraints during feasibility — before you’re invested in a specific ADU location. If your property is in Madison and has significant trees, bring it up in the first conversation.