Retaining Walls: Kailua vs Urban Honolulu
How do retaining walls rules compare between Kailua, HI and Urban Honolulu, HI?
Urban Honolulu has fewer restrictions than Kailua.
Kailua, HI
Honolulu County
Retaining walls in Kailua follow ROH Sec. 21-4.40, which caps fill-retention walls within required yards at 6 feet. Terraced walls count toward combined height totals, and most walls over 30 inches require engineering.
View full Kailua 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 | Kailua | Urban Honolulu |
|---|---|---|
| - | - | |
| Max height | - | 6 feet |
| Terracing rule | - | Combined height |
| Permit trigger | - | Over 30 inches |
| Code section | - | ROH 21-4.40 |
Highlighted rows indicate differences between cities.
Kailua FAQ
Can I build a 5-foot retaining wall in my side yard?
Yes, up to 6 feet within required yards under ROH 21-4.40, but you will likely need a permit and engineering over 30 inches.
What about two stacked 4-foot walls?
Terraced walls are typically measured together, so two closely spaced 4-foot walls may be treated as an 8-foot wall exceeding the cap.
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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