Retaining Walls: East Honolulu vs Mililani Mauka
How do retaining walls rules compare between East Honolulu, HI and Mililani Mauka, HI?
East Honolulu and Mililani Mauka have similar restriction levels.
East Honolulu, HI
Honolulu County
East Honolulu retaining walls on Kuliouou, Hawaii Loa Ridge, and Niu Valley hillsides fall under ROH 21-4.40, which caps fill-bearing walls in required yards at 6 feet with terraced heights combined.
View full East Honolulu rules →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 →Key Facts Comparison
| Fact | East Honolulu | Mililani Mauka |
|---|---|---|
| Yard max height | 6 feet | - |
| Terraced rule | Heights combined | - |
| Code section | ROH 21-4.40 | - |
| Engineering trigger | Above 30 inches | - |
| - | - |
Highlighted rows indicate differences between cities.
East Honolulu FAQ
How tall can a Hawaii Kai retaining wall be?
Walls containing 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 hillside lots.
Do Kuliouou hillside walls need extra review?
Yes. Steep Kuliouou and Hawaii Loa Ridge sites typically require geotechnical and drainage review, engineered drawings, and sometimes grading permits under Chapter 14 alongside the 21-4.40 retaining wall rules.
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.
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