Retaining Walls: Honolulu vs Pearl City

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.

How tall can a Pearl City 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, and engineering review is required above the 30-inch permit threshold on hillside lots.

Do hillside walls need extra review?

Yes. Pearl City Highlands and Manana hillside sites typically require geotechnical and drainage review, engineered drawings, and Chapter 14 grading coordination alongside the 21-4.40 retaining wall rules.