Retaining Walls: Honolulu vs Waipahu
How do retaining walls rules compare between Honolulu, HI and Waipahu, HI?
Honolulu has fewer restrictions than Waipahu.
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 →Waipahu, HI
Honolulu County
Waipahu retaining walls fall under ROH 21-4.40, capping fill-bearing walls in required yards at 6 feet with terraced heights combined, impacting stream-side and hillside plantation lots.
View full Waipahu rules →Key Facts Comparison
| Fact | Honolulu | Waipahu |
|---|---|---|
| Max in required yard | 6 feet | - |
| Terracing rule | Combined heights counted | - |
| Permit trigger | Over 30 inches | - |
| Code section | ROH 21-4.40 | ROH 21-4.40 |
| Yard max height | - | 6 feet |
| Terraced rule | - | Heights combined |
| Drainage overlay | - | Chapter 14 |
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.
Waipahu FAQ
How tall can a Waipahu 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. Engineering review is required above the 30-inch permit threshold for taller installations.
Do old rock walls still comply?
Many legacy plantation-era rock walls are grandfathered. However, substantial alteration, repair, or replacement triggers current ROH 21-4.40 standards and may require engineered drawings plus drainage review.
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