Sonoma County, CA Outdoor Lighting: Light Trespass (2026)

Light trespass, light spilling from one property onto another, is controlled in unincorporated Sonoma County through development standards in the County Zoning Regulations (Chapter 26) and the design-review process (Article 82), rather than a stand-alone trespass ordinance applying to all yard lighting. Across multiple special-use standards in Article 88, exterior lighting must be fully shielded and downward-casting so that it does not wash out onto structures, neighboring properties, or the night sky. For certain regulated uses, the County imposes a numeric spillover limit, such as total illuminance beyond the property line not exceeding 1.0 lux and fixtures not exceeding 1,000 lumens in specified contexts. Solar facilities must not direct concentrated reflections or glare at occupied structures, recreation areas, roads, highways, or airports (Sec. 26-88-206). Projects subject to design review under Sec. 26-82-050 are evaluated to ensure lighting does not produce glare or spillover affecting adjacent parcels. For ordinary residential lighting not tied to a regulated use or discretionary permit, complaints about a neighbor's light shining onto your property are typically handled as nuisance matters or through the design-review conditions on the project that created the lighting. Owners installing significant exterior lighting should aim fixtures downward, shield the source, and avoid directing light or glare across property lines.