Sammamish, WA Fence Regulations: Retaining Walls (2026)
Key Facts
- Retaining wall exemption
- Up to 4 ft, footing to top of wall
- Rockery wall exemption
- Up to 4 ft, grade to top of wall
- Never exempt
- Walls with a surcharge or Class I-III-A liquids
- Over 4 ft
- Requires building permit under SMC 16.20.195
- Critical areas
- Exemption void in critical areas/shoreline setbacks
Summary
Sammamish exempts retaining and rockery walls up to four feet from a building permit, but SMC 16.20.200(2)(d)-(e) draws the line there: taller walls, or any wall bracing a surcharge or holding back Class I, II or III-A liquids, need a full building permit and typically engineered plans.
(d) Retaining walls which are not over four feet (1,219 mm) in height measured from the bottom of the footing to the top of the wall, unless supporting a surcharge or impounding Class I, II or III-A liquids. (e) Rockery walls which are not over four feet (1,219 mm) in height measured from finished grade to the top of the wall, unless supporting a surcharge or impounding Class I, II or III-A liquids.
Official source re-checked September 8, 2026: no newer edition of the code had been published (publisher’s edition: current through Ordinance O2026-598, and legislation passed through August 18, 2026).
Full Breakdown
200(2)(d) exempts retaining walls that are not over four feet, measured from the bottom of the footing to the top of the wall, from a City building permit, and subsection (2)(e) gives rockery walls the same four-foot exemption, measured from finished grade to the top of the wall. Both exemptions have a built-in exception: a wall of any height that supports a surcharge, such as a slope, driveway or structure load behind it, or that impounds Class I, II or III-A flammable or combustible liquids, is never exempt and needs a permit regardless of height.
195, which requires the owner or an authorized agent to apply to the permit center and obtain a permit before construction, alteration or repair. 200 further narrows the exemption on Sammamish's Plateau lots: permit exemptions for work outside the footprint of an existing legally established structure do not apply within critical areas or within standard shoreline setbacks, so a wall near a wetland, stream or steep slope buffer can lose its under-four-foot exemption even if it would otherwise qualify.
Violations & Fines
Building a retaining or rockery wall over four feet, or one that impounds liquids or carries a surcharge, without first getting a permit exposes the owner to a stop work order and special investigation fee under SMC 16.20.355, plus civil penalties under Chapter 23.100 SMC if work continues after the order. The building official may also require an engineer's certification of the wall's structural integrity before it can be permitted after the fact.
Frequently Asked Questions
How tall can my retaining wall be without a permit in Sammamish?
Does a low wall ever need a permit anyway?
What is the penalty for building an unpermitted retaining wall over four feet?
Sources & Official References
Other rules in Sammamish
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Retaining Walls in Nearby Cities
How other cities in King County handle retaining walls.