Retaining Walls: Honolulu vs Urban Honolulu
How do retaining walls rules compare between Honolulu, HI and Urban Honolulu, HI?
Honolulu and Urban Honolulu have similar restriction levels.
Honolulu, HI
Honolulu County
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.
View full Honolulu rules →Urban Honolulu, HI
Honolulu County
Urban Honolulu limits retaining walls that contain fill within required yards to 6 feet under ROH 21-4.40 and combines terraced wall heights to prevent stacking around hillside lots.
View full Urban Honolulu rules →Key Facts Comparison
| Fact | Honolulu | Urban Honolulu |
|---|---|---|
| Max in required yard | 6 feet | - |
| Terracing rule | Combined heights counted | Combined height |
| Permit trigger | Over 30 inches | Over 30 inches |
| Code section | ROH 21-4.40 | ROH 21-4.40 |
| Max height | - | 6 feet |
Highlighted rows indicate differences between cities.
Honolulu FAQ
How tall can a retaining wall be in Honolulu County?
Under ROH 21-4.40, retaining walls containing fill within required yards cannot exceed 6 feet. Terraced walls are combined for measurement, so stacking shorter walls does not avoid the limit.
Do retaining walls need a permit in Honolulu?
Retaining or riprap walls 30 inches or shorter are exempt under ROH 18-3.1. Taller retaining walls require a Honolulu DPP building permit and often engineered drawings.
Urban Honolulu FAQ
How tall can a retaining wall be in Urban Honolulu?
Under ROH 21-4.40, retaining walls containing fill within required yards cannot exceed 6 feet. Terraced walls on hillside lots in neighborhoods like Manoa are measured as one combined wall.
Does a hillside retaining wall need a permit in Honolulu?
Yes, if it exceeds 30 inches. ROH 18-3.1 exempts only walls 30 inches or shorter. Honolulu DPP typically requires engineered plans, drainage, and guardrails for larger hillside retaining walls.
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