Lower Merion, PA Outdoor Lighting: Light Trespass & Shielding (2026)

Section 105-12.C(1) of the Lower Merion Township Code sets numeric light-trespass limits in Table 13.3, measured as maximum vertical illuminance at any point in the perimeter plane of the property. Lots with conforming structures in the LDR 1-3 Districts, and any spot where a non-residential use abuts a residential use or district, are held to 0.1 footcandle. Locations adjacent to medium- or high-density residential districts, including LDR 4 and MDR 1-3, or adjacent to non-conforming structures in the LDR 1-3 Districts, are allowed 0.2 footcandle.

Sites adjacent to a compatible non-residential use or district get the loosest limit, 0.3 footcandle. Section 105-12.B(2) backs the trespass table with a mounting-height ceiling: luminaires cannot be mounted higher than 12 feet above finished grade of the surface being illuminated, unless the applicant demonstrates that a taller fixture would not increase light trespass or glare onto adjacent properties. Section 105-12.C(2) adds a companion Allowable Luminaire Glare Rating table (13.4) that limits fixture glare by zone depending on the abutting use. The Township's LIGHT TRESPASS definition in Section 105-11, light that falls beyond the property it is intended to illuminate, frames why these numbers exist: they stop a commercial or larger residential lot's lighting plan from washing out a neighbor's yard or windows.

Compliance is checked at permit stage under Section 105-12.C, which for Major Lighting Submissions requires a Point Method illumination plan extending 10 feet beyond the property lines.