Retaining Walls: East Honolulu vs Honolulu

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.

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.