Development on slopes above 15% in Boise's Foothills triggers the Hillside and Foothills overlays, which restrict cuts, fills, building footprints, and landscape choices to protect viewsheds, wildfire safety, and the Boise Foothills Conservation Easement.
The Modern Zoning Code carries forward and strengthens Boise's longstanding hillside development regulations. Sites with average slopes between 15% and 25% face graduated standards on grading, retaining-wall height, paint-color reflectivity, and lot coverage. Slopes above 25% require additional geotechnical review and are discouraged. The overlay also enforces fire-resistant landscape lists, defensible-space buffers, and trail dedications that link to the Ridge to Rivers system. Adjacent conservation easements held by the Land Trust of the Treasure Valley further limit subdivision in the upper Foothills.
Grading or building outside approved hillside plans triggers stop-work orders, restoration requirements, and daily fines under Title 11. Repeat violations can void the development approval.
See how Boise's hillside overlay rules rules stack up against other locations.
Help us keep this page accurate. If you notice an error or outdated information, let us know.