Williamson County, TN Outdoor Lighting: Dark Sky Rules (2026)
Key Facts
- Full cut-off trigger
- Fixtures over 1,000 lumens
- Direction required
- All lighting directed downward
- Exempt uses
- Mobile homes, single-family homes, street lights
- Max fixture height, residential
- 20 feet
- Max fixture height, industrial/ag
- 30 feet
- Review point
- Lighting/photometric plan at Site Plan filing
Summary
Non-residential development in unincorporated Williamson County must aim outdoor light fixtures downward and shield anything over 1,000 lumens with a full cut-off lens or hood. The rule, reviewed at Site Plan submission with a photometric plan, exempts mobile homes, single-family dwellings and street lighting.
(2) No flickering or flashing light shall be permitted. (3) Light sources or luminaires shall not be located within required bufferyards except for pedestrian-scaled lighting along walkways. (4) All lighting shall be directed downward except for low-wattage architectural lighting intended to illuminate structures. ... (6) Light fixtures in excess of 1,000 lumens shall use full cut-off lenses or hoods to prevent glare or spillover onto adjacent parcels and streets. (7) No light source in a canopy structure shall extend downward further than the lowest edge of the canopy's ceiling.
Full Breakdown
03(B) of the Williamson County Zoning Ordinance, effective January 1, 2013, applies to every use listed in the county's Table of Allowed Uses except mobile homes, single-family dwellings and street lighting (Sec. 03(A)). 03(B)(1). Flickering or flashing lights are banned outright under (B)(2), and light sources cannot sit inside required bufferyards except pedestrian-scale walkway lighting under (B)(3). The core shielding rule is two-part: all lighting must be directed downward, with an exception only for low-wattage architectural lighting that illuminates a structure's facade (B)(4), and any fixture producing more than 1,000 lumens must use a full cut-off lens or hood to prevent glare or spillover onto adjacent parcels and streets (B)(6). A related rule bars canopy lighting, such as at a gas station, from extending below the canopy's own ceiling line (B)(7). 03(C).
Violations & Fines
Installing or operating an unshielded fixture above 1,000 lumens, or lighting aimed upward or outward rather than down, is a zoning violation under Article 22, punishable as a misdemeanor under Section 22.07(A) with a fine of $10 to $50 per offense and each day of noncompliance treated as a separate offense under 22.03(F). The Codes Compliance Director can also revoke the associated Zoning Certificate under Section 22.06(C) until the fixtures are brought into compliance.
Frequently Asked Questions
At what brightness does a fixture need a full cut-off shield in Williamson County?
Does the outdoor lighting rule apply to my house?
Can a gas station light its canopy however it wants?
What happens if a business installs unshielded lighting anyway?
Sources & Official References
Other rules in Williamson County
Compare Williamson County to another location·View the Tennessee outdoor lighting overview
See something wrong?
Help us keep this page accurate. If you notice an error or outdated information, let us know.