King County, WA Sign Regulations: Digital Billboards (2026)
Key Facts
- Changing-message zones
- NB, CB, RB, O, I only
- RA schools
- 7 a.m.-10 p.m. hours only
- Billboard face cap
- Frozen at 1988 count
- Billboard zones
- CB, RB, I only
Summary
Unincorporated King County limits electronic changing-message signs to commercial and industrial zones and freezes the total count of billboard faces at 1988 levels, so a new digital billboard generally requires replacing an existing one.
Changing message center signs, and time and temperature signs, which can be a wall or freestanding sign, shall not exceed the size permitted for a wall or freestanding sign. Changing message center signs shall be permitted for all uses only in the NB, CB, RB, O and I zones and only for elementary, middle, junior, secondary and high schools and colleges and universities in the RA zone. Changing message center signs and time and temperature signs shall not exceed the maximum sign height permitted in the zone.
E. Directional signs shall not be included in the sign area or number limitation of K.C.C. 21A.20.070, 21A.20.095, 21A.20.100 and 21A.20.110, but only if the signs do not exceed six square feet in surface area and are limited to one for each entrance or exit to surface parking areas or parking structure.
F. Regarding sign illumination and glare:
1. Except as otherwise provided in this chapter, all signs may be illuminated;
2. The light source for indirectly illuminated signs shall be no farther away from the sign than the height of the sign;
3. Indirectly and directly illuminated signs shall be arranged so that no direct rays of light are projected from such artificial source into residences or any street right-of-way;
4. Electrical requirements for signs shall be governed by chapter 19.28 RCW and WAC 296-46-910; and
5. Signs with an on/off operation shall be permitted only in the CB, RB and I zones.
Full Breakdown
King County restricts electronically controlled 'changing message center' signs, those that change more than once every three minutes, to the NB, CB, RB, O and I zones; RA-zone schools may run one, but only 7 a.m. to 10 p.m. Off-premise billboards face a harder limit: K.C.C. 21A.20.140 freezes the total billboard-face count in unincorporated King County at the number existing on June 20, 1988, so a new digital billboard generally requires replacing an existing face in a CB, RB or I zone. This is unincorporated-county law only, Seattle, Bellevue, Kent, Renton and other cities set their own sign codes.
Violations & Fines
Altering, relocating or exceeding the frozen billboard-face count without a Department of Local Services alteration/relocation permit under K.C.C. 21A.20.160 is a code violation subject to permit revocation and mandatory removal.
Frequently Asked Questions
Can I put up a new digital billboard in unincorporated King County?
Are LED or electronic message signs allowed on regular business signs?
Sources & Official References
Other rules in King County
Compare King County to another location·View the Washington sign regulations overview
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