Honolulu County's LUO Section 21-3.70-1 caps impervious surface at 75 percent of lot area for residential dwellings permitted after May 1, 2019, to control runoff and preserve neighborhood character.
ROH/LUO Section 21-3.70-1 establishes residential use and development standards for Oahu and sets the impervious-surface or lot-coverage caps that govern how much of a lot may be occupied by buildings, driveways, patios, and other hard surfaces. Dwellings permitted after May 1, 2019, are limited to 75 percent impervious coverage, a rule added to reduce stormwater runoff into Honolulu's drainage system and coastal waters. Floor area ratio, number of bedrooms, parking counts, and accessory dwelling unit standards also appear in this section. The section works in concert with ROH 21-4.30 setbacks and 21-4.60 heights to shape the overall building envelope on residential lots across Oahu.
Exceeding the 75 percent impervious cap can require removal of paving, installation of pervious alternatives, daily civil penalties, and denial of permits until runoff calculations and site plans are brought into compliance.
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See how Honolulu County's lot coverage limits rules stack up against other locations.
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