Whatcom County, WA Fence Regulations: Retaining Walls (2026)
Key Facts
- Permit-exempt height
- 4 feet (1,219 mm) unbalanced backfill
- Exceptions that void exemption
- Surcharge, steep slope, flammable liquids
- Over 4 feet
- Full permit and possible engineering
- Misdemeanor penalty
- Up to $1,000 or 90 days
- Permit validity
- 2 years, one 1-year extension
Summary
A retaining wall in unincorporated Whatcom County is permit-exempt only if it holds back 4 feet or less of unbalanced backfill, per WCC § 15.04.030(C)(3). Support a surcharge, sit on a steep slope, or hold back flammable liquids, and the exemption disappears no matter how short the wall is.
3. Retaining walls that do not retain more than 4 feet (1,219 mm) of unbalanced back fill in height differential measured from the lower finished ground level and upper finished ground level, unless supporting a surcharge, or grades exceeding a 1:3 slope above or below the wall or impounding Class I, II, or IIIA liquids.
Official source re-checked September 7, 2026: no newer edition of the code had been published (publisher’s edition: rev 4963078; v4 updated 2026-06-23; through 06-23-2026).
Full Breakdown
020(C)(2)(3). Three conditions strip the exemption even from a wall under 4 feet: the wall supports a surcharge load, the grade above or below the wall exceeds a 1:3 slope, or the wall impounds Class I, II, or IIIA flammable or combustible liquids. Any wall over 4 feet always needs a full building permit, and PDS Building Services can require an engineer's or architect's stamped design for taller or load-bearing walls, particularly on the sloped and unstable ground common in the county's foothill and river-valley areas. 050.
Violations & Fines
Building a retaining wall that exceeds 4 feet, or that meets one of the surcharge, slope, or liquid-impoundment exceptions, without a permit is a misdemeanor under WCC § 15.04.050(D), punishable by a fine of up to $1,000, up to 90 days in jail, or both, with each day of the violation a separate offense. The county can instead levy a civil penalty of up to $1,000 per day under WCC § 15.04.050(F); the property owner has 30 days to seek mitigation and 10 days to appeal to the county council.
Frequently Asked Questions
How tall can a retaining wall be in Whatcom County without a permit?
Does a permit-exempt retaining wall still need engineering?
What's the penalty for building an unpermitted retaining wall?
Sources & Official References
Other rules in Whatcom County
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