Retaining Walls: Pearl City vs Urban Honolulu
How do retaining walls rules compare between Pearl City, HI and Urban Honolulu, HI?
Urban Honolulu has fewer restrictions than Pearl City.
Pearl City, HI
Honolulu County
Pearl City retaining walls on the Pearl City Highlands and Manana hillsides fall under ROH 21-4.40, capping fill-bearing walls in required yards at 6 feet and combining terraced heights.
View full Pearl City 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 | Pearl City | Urban Honolulu |
|---|---|---|
| Yard max height | 6 feet | - |
| Terraced rule | Heights combined | - |
| Code section | ROH 21-4.40 | ROH 21-4.40 |
| Drainage review | Chapter 14 | - |
| Max height | - | 6 feet |
| Terracing rule | - | Combined height |
| Permit trigger | - | Over 30 inches |
Highlighted rows indicate differences between cities.
Pearl City FAQ
How tall can a Pearl City retaining wall be?
Walls with fill in a required yard cap at 6 feet under ROH 21-4.40. Terraced walls are measured as combined height, and engineering review is required above the 30-inch permit threshold on hillside lots.
Do hillside walls need extra review?
Yes. Pearl City Highlands and Manana hillside sites typically require geotechnical and drainage review, engineered drawings, and Chapter 14 grading coordination alongside the 21-4.40 retaining wall rules.
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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