Honolulu County, HI Fence Regulations: Retaining Walls (2026)
Key Facts
- Fill retaining walls
- 6 ft max
- Cut-only retaining walls
- no height limit
- Combined cut+fill wall
- 6 ft max
- Safety railing add-on
- up to 6 ft more
Summary
Honolulu caps retaining walls that hold back fill within a required yard at 6 feet, measured from grade to the top of the exposed wall face, under the Land Use Ordinance.
Retaining walls containing a fill within required yards shall not exceed a height of 6 feet, measured from existing or finished grade, whichever is lower, to the top of the wall along the exposed face of the wall. Heights of terraced walls or combinations of retaining walls shall be measured combining all walls located in the required yard (see Figures 21-4.2(A) and (B)).
(b) A retaining wall that protects a cut below the existing grade may be constructed within a required yard, up to the height of the cut. There shall be no height limit for retaining walls that protect a cut; provided that a retaining wall that protects a cut and contains fill shall not exceed a total of 6 feet in height measured from the intersection of the wall and the existing or finished grade, whichever is lower, to the top of the wall along the exposed face of the wall.
(c) A safety railing may be erected on top of any retaining wall within a required yard. If the safety railing is generally constructed of a different material than the retaining wall, and is open at intervals so as not to be capable of retaining earth, it shall not exceed a height of 6 feet above the retaining wall.
(d) Safety railing or fences constructed of the same materials as the retaining wall shall not exceed a total combined height of 6 feet measured from the finished grade along the exposed face of the wall. Additional fence height of different material not capable of retaining material may be erected, not to
Official source re-checked September 7, 2026: no newer edition of the code had been published (publisher’s edition: 2026 S-10: Supplement 10, 12-2025 Ordinance No. 25-40 through Ordinance No. 25-56).
Full Breakdown
ROH § 21-4.40 sets separate rules by wall type: a retaining wall holding back fill in a required yard cannot exceed 6 feet, with terraced or combined walls measured together. A wall that only protects a cut below existing grade has no height limit, but if it also contains fill the combined height is still capped at 6 feet. A safety railing of open, different material may add up to 6 feet more on top without counting toward the wall's own height limit.
Violations & Fines
Building a fill retaining wall over 6 feet without qualifying as a cut wall is a Land Use Ordinance violation; the Department of Planning and Permitting can require the wall be lowered or removed to conform.
Frequently Asked Questions
How tall can a retaining wall be in Honolulu?
Can I add a railing on top of a retaining wall?
Sources & Official References
Other rules in Honolulu County
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