A retaining wall four feet or higher requires a building permit in Hawaii County, and grading or filling 100 cubic yards or reaching five feet vertical also needs a grading permit. Zoning still treats walls over six feet as accessory structures barred from required yards.
The County building-permit guidelines require a permit for any "Retaining wall (concrete, CMU, rock, or other) 4-feet or higher," and plans are required for retaining walls over four feet. Separately, a grading and/or grubbing permit under HCC Chapter 10 is required for excavation or filling of 100 cubic yards on any site reaching five feet in vertical height at its highest point. Zoning Code 25-4-43(c) also treats any wall over six feet as an accessory structure that cannot project into a required front, side, or rear yard.
Unpermitted retaining walls or grading can draw a stop-work order, after-the-fact permitting with doubled fees, engineering review, and required correction.
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See how Hawaii County's retaining walls rules stack up against other locations.
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