Retaining Walls: Mililani Mauka vs Waipahu
How do retaining walls rules compare between Mililani Mauka, HI and Waipahu, HI?
Mililani Mauka and Waipahu have similar restriction levels.
Mililani Mauka, HI
Honolulu County
ROH Sec. 21-4.40 limits fill-retaining walls in Mililani Mauka yards to six feet and combines terraced wall heights, important on the community's sloped Central Oahu grades.
View full Mililani Mauka 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 Mauka | 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 Mauka FAQ
Can I build a three-tier terrace instead of one tall wall?
Terraced walls are measured together under ROH 21-4.40, so stacking tiers does not sidestep the six-foot limit.
Must retaining wall finishes be approved by MTA?
Yes. Walls visible from the street typically require MTA approval for color and finish.
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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