Knox County, TN Sign Regulations: Digital Billboards (2026)
Key Facts
- Allowed districts
- CA, CB, CH, PC, SC, I, LI, BP, EC only
- Minimum hold time
- 60 seconds per display
- Daytime brightness cap
- 3,000 nits
- Nighttime brightness cap
- 750 nits
- Property-line light cap
- 0.2 footcandles
- Wall sign size cap
- 100 square feet maximum
Summary
Knox County allows digital billboards, called electronic message centers, only as part of a wall or monument sign in the CA, CB, CH, PC, SC, I, LI, BP and EC commercial and industrial zones, never as a stand-alone sign or in a residential or agricultural district. Zoning Ordinance Sec. 3.90.02.Q caps brightness at 3,000 nits by day and 750 nits at night, requires automatic dimming, and holds each display in place for 60 seconds before it can change.
Q.Electronic message centers may be permitted as part of a wall or monument sign in CA, CB, CH, PC, SC, I, LI, BP and EC zone districts in accordance with the following regulations... 5.An EMC permitted as part of a ground or monument sign shall have a minimum matrix area of twenty (20) square feet and a maximum size of one-third (⅓) of the total signage permitted or one hundred (100) square feet, whichever is less.6.An EMC permitted as a wall sign shall not exceed one hundred (100) square feet maximum.7.Each display on an EMC shall hold constant for a minimum of sixty (60) seconds.8.An EMC shall not display light of such intensity or brightness to cause glare... Daytime maximum brightness 3,000 nits; Nighttime maximum brightness 750 nits; Maximum brightness at the property line 0.2 footcandles.
Official source re-checked September 7, 2026: no newer edition of the code had been published (publisher’s edition: Code of Ordinances: Supplement 23).
Full Breakdown
Under Sec. Q, an electronic message center, the county's term for a digital billboard-style display, is permitted only as a wall sign or as an integrated part of a ground or monument business sign, and only in the CA, CB, CH, PC, SC, I, LI, BP and EC zoning districts; no EMC is allowed as a stand-alone billboard or in a residential or agricultural district. A ground or monument-mounted EMC must have a matrix area of at least 20 square feet and cannot exceed one-third of the total signage allowed on the parcel or 100 square feet, whichever is smaller; a wall-mounted EMC is capped at 100 square feet outright.
Every display has to hold for a minimum of 60 seconds, the code bans any animation or special-effects transition between messages, and images must be complete in themselves, without continuation in content to the next image. 2 footcandles, enforced through a mandatory automatic dimmer tied to a light sensor. The section also sets a sliding minimum text height keyed to the posted speed limit on the frontage road, from 7 inches at 25 to 34 mph up to 15 inches at 55 mph and above; if the sign face is too small to fit that size, no text is allowed at all.
EMCs already operating on April 10, 2009 may continue, and any EMC operating as of June 12, 2013 had to meet the hold-time, brightness, and text-size standards regardless of when it was installed.
Violations & Fines
Building a sign before securing a permit doubles the required fee under Sec. 3.90.02.O. Beyond that, an EMC that runs brighter than the nit limits, fails to hold a message for 60 seconds, or uses animation is a zoning violation under the general enforcement section, Sec. 6.20.02.A: a civil penalty of $10 to $500, with each day of continued violation counted separately, appealable to the board of zoning appeals.
Frequently Asked Questions
Can a digital billboard be built as its own free-standing sign in Knox County?
How bright can an electronic message center be?
How long does each message have to stay up?
Sources & Official References
Other rules in Knox County
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