Sammamish, WA Outdoor Lighting: Light Trespass (2026)

Light trespass - unwanted light spilling from one property onto a neighbor's - is addressed directly in the Sammamish Development Code's exterior-lighting design standards at SMC 21.06.020. The code requires outdoor light fixtures to be fully shielded, pointed downward, and maintained in a way that causes minimal or no light trespass onto adjacent properties. By requiring full shielding and downward aim, the standard conceals the light source from neighboring lots and limits horizontal spillover and glare. Outdoor lighting may also not exceed 5.0 lumens per square foot of hardscape outside the building structure, which caps overall brightness. Limited exceptions exist for modest fixtures: one partially shielded sconce beneath a building overhang generating less than 630 lumens, and landscape or accent lighting whose combined output does not exceed 2,100 lumens. Together these provisions function as the city's anti-light-trespass framework, balancing security and entry lighting against neighbors' interest in avoiding nuisance glare and spillover. Sammamish does not publish a separate numeric light-trespass measurement (such as a foot-candle limit at the property line) in this guidance, so the operative test is the performance standard of 'minimal or no light trespass' combined with the shielding and lumen caps. Owners experiencing or causing spillover should review fixture shielding and aim first, then confirm current requirements and any nuisance remedies with the Sammamish Permit Center or code-compliance staff.