Honolulu's LUO Section 21-4.40 limits retaining wall heights in required yards to 6 feet when containing fill and combines terraced wall heights for measurement purposes island-wide.
ROH/LUO Section 21-4.40 is the island-wide rule specifically for retaining walls on Oahu. Retaining walls that contain fill within a required yard cannot exceed 6 feet in height. Where terraced walls are used, the code measures their combined height for compliance purposes, preventing stacked walls from bypassing the 6-foot limit. Walls supporting driveways, pools, or garages must also satisfy Building Code structural requirements and may need a permit when they exceed 30 inches per ROH 18-3.1. Drainage, weep holes, and guardrails on top of retaining walls over 30 inches are required. Walls near public rights-of-way may require additional review by the Department of Transportation Services.
Exceeding the 6-foot height limit or failing to permit a retaining wall over 30 inches can trigger stop-work orders, required engineering re-design, daily civil fines, and demolition when drainage or safety standards are not met.
Honolulu County, HI
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Honolulu County, HI
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See how Honolulu County's retaining walls rules stack up against other locations.
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