Retaining Walls: Mililani Town vs Waipahu
How do retaining walls rules compare between Mililani Town, HI and Waipahu, HI?
Mililani Town and Waipahu have similar restriction levels.
Mililani Town, HI
Honolulu County
Mililani Town retaining walls follow ROH Sec. 21-4.40 rules and HOA review. Fill-retaining walls in required yards cannot exceed 6 feet, and terraced walls are measured in combination.
View full Mililani Town 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 | Mililani Town | Waipahu |
|---|---|---|
| - | - | |
| Yard max height | - | 6 feet |
| Terraced rule | - | Heights combined |
| Code section | - | ROH 21-4.40 |
| Drainage overlay | - | Chapter 14 |
Highlighted rows indicate differences between cities.
Mililani Town FAQ
Do planter walls count as retaining walls?
If they hold back soil, yes; decorative low planters that don't retain earth are typically not regulated under 21-4.40.
Is HOA approval needed for a 24-inch garden wall?
Usually yes. Even ROH-exempt walls typically still need HOA architectural review in Mililani before construction.
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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