Tree review (SMC 25.11) if regulated trees apply

When tree review applies

SDCI's tree protection code (SMC 25.11) regulates trees on residential lots. The thresholds:

• Significant trees — generally 12 inches DBH or more in residential zones.
• Exceptional trees — designated for size, species, or historic value; protected at any size.
• Trees in the public right-of-way — always regulated, separately reviewed by Seattle's Department of Transportation.

A whole-house remodel rarely removes trees, but the addition's footprint or construction staging often falls within a regulated tree's protection zone (CRZ — typically 1 ft of radius per inch of DBH). When it does:

• Tree preservation plan required, drawn on the survey.
• Construction fencing to protect the CRZ during construction.
• Arborist sign-off if any work enters the CRZ.

How to handle it

For most additions, the designer flags any nearby regulated tree on the survey and produces a tree-protection plan with the submittal. SDCI accepts most preservation plans without conditions; the project clears tree review concurrently with the main permit.

If a regulated tree has to be removed, the path is more involved: arborist's report, justification, mitigation planting, separate tree permit. Removal is rarely worth it on a single-story addition; redesign around the tree if you can.

When you can skip this concern

Lots with no regulated trees on or near them — most inner-city Seattle lots don't have any — pass through tree review without comments. The designer flags "no regulated trees on lot" in the submittal and SDCI accepts.