Honolulu Lot Coverage and FAR: How DPP Calculates Your Buildable Envelope
Lot coverage and floor area ratio are two distinct calculations that together define how much can be built on a given parcel. Both are required on every Honolulu building permit submission, and both are frequent sources of plan check comments — not because the math is complex, but because what counts toward each figure is frequently misunderstood.
Lot coverage: the basic definition
Lot coverage measures the proportion of a lot's area that is occupied by structures — specifically, the horizontal footprint of all covered structures on the lot, expressed as a percentage of the total lot area.
Under ROH Chapter 21, each zoning district specifies a maximum lot coverage percentage. For residential districts:
- R-3.5 and R-5 districts: typically 50% maximum lot coverage
- R-7.5 and above: typically 40% maximum lot coverage
- Apartment and business districts: vary by district — consult the district-specific standards
These figures are representative. Verify the exact maximum for the specific zoning district against the current adopted ROH Chapter 21 text.
The calculation is straightforward: sum the footprint of all covered structures, divide by the lot area, multiply by 100. The challenge is correctly identifying which structures are included in the numerator.
What counts toward lot coverage
| Structure or element | Counts? | Notes |
|---|---|---|
| Primary dwelling footprint | Yes | All area within the exterior walls at grade. |
| Attached garage | Yes | Counted at full footprint regardless of whether it is enclosed or open-sided. |
| Detached accessory structure | Yes | Includes ohana units, storage buildings, workshops, and pool houses. |
| Covered lanai — attached, open sides | Yes | A roofed area attached to the primary structure counts at full footprint. The open sides do not create an exemption. |
| Covered lanai — detached pergola, open top | No | An open-top trellis or pergola with no solid roof covering is generally not counted as lot coverage. If more than 50% of the overhead area is solid material, the entire footprint is typically counted. |
| Carport — attached to dwelling | Yes | Attached carport counted at full footprint. |
| Swimming pool | No | Pool water area does not count as lot coverage. Surrounding pool deck, if covered, would count. |
| Driveway and paving | No | Paved surfaces are not lot coverage for LUO purposes (though they are relevant to impervious surface calculations for drainage). |
| AC equipment pads and mechanical equipment | No | Unroofed mechanical equipment pads do not count as lot coverage. |
| Roof overhang beyond 18 inches | Yes | Roof overhangs extending more than 18 inches beyond the wall count as lot coverage. The 18-inch overhang tolerance is commonly misapplied — measure from the exterior face of the wall, not the drip edge. |
Verify treatment of specific elements against current ROH Chapter 21 definitions — LUO definitions are controlling.
Floor area ratio (FAR): what it measures and when it applies
Floor area ratio measures the total floor area of all structures on a lot divided by the lot area. A FAR of 0.5 on a 5,000 square foot lot allows 2,500 square feet of total floor area. FAR limits the total building mass independently of the footprint — a two-story building with a small footprint can still exceed FAR even if it complies with lot coverage.
FAR applies primarily to apartment and commercial districts in Honolulu. Most residential (R) districts in Honolulu do not have a FAR limit — they are regulated by lot coverage, setbacks, and height. If your project is in a district that does not impose FAR, you do not need to calculate or document it. Verify for the specific district.
For districts where FAR applies, the calculation requires knowing what floor area is counted. The LUO definition of floor area includes:
- All enclosed floor area on all floors, measured to the exterior face of the exterior walls
- Enclosed parking area within the building (though some districts exempt a portion of structured parking from FAR)
- Enclosed mechanical rooms, storage, and utility areas
Floor area that is typically excluded from FAR calculation under the LUO:
- Open parking areas and driveways
- Unenclosed lanais and balconies (subject to conditions — if enclosed on more than two sides, may be counted)
- Attic space with limited headroom (below a specified height threshold, typically 5 feet)
- Basement area, in some district standards
How to show the calculation on your drawings
DPP expects the lot coverage and FAR calculations to appear on the site plan or in the general notes. A compliant calculation block should include:
The line-item breakdown is important. A single number ("lot coverage = 49.9%") without the component breakdown does not allow the plan checker to verify the calculation and will result in a comment requesting the breakdown.
Common calculation errors that generate comments
- Omitting the ohana unit or ADU footprint. Secondary units are covered structures. Their footprint counts toward lot coverage along with the primary dwelling. On small lots, this is the most common reason an ohana unit project exceeds the district maximum.
- Measuring lot area from the wrong document. The lot area should come from the recorded subdivision plat or a current survey. Using the County tax records area or a GIS estimate can introduce errors. If there is a discrepancy, the surveyed area controls.
- Applying the 18-inch overhang tolerance incorrectly. The 18-inch tolerance is measured from the exterior face of the wall, not from the centerline of the wall or from the interior face. On thick-wall construction, the difference can be meaningful.
- Missing the covered lanai. Architects sometimes omit covered lanais from the lot coverage calculation on the assumption that open sides make them non-structures. Under the LUO, a covered area — even with fully open sides — is counted at its full footprint.
- Inconsistency between site plan dimensions and the calculation. If the site plan shows the covered lanai as 12 feet by 20 feet but the lot coverage calculation uses 200 square feet (10 by 20), the plan checker will flag the inconsistency. Every number in the calculation must be verifiable from the drawings.
- Not accounting for proposed future structures.A calculation block that shows compliance today but does not include a structure shown on the drawings as "future" will be questioned. DPP will ask whether the future structure was included in the lot coverage calculation.
Lot coverage calculated from your actual drawings.
Ikena Permit extracts footprint areas from your plan set, applies the ROH Chapter 21 definition of covered structure, and returns a compliant calculation block you can paste directly into your site plan notes — along with a flag if the project is within 5% of the district maximum.
Request early access →Published by Ikena Permit, a DBA of Ikena Design & Build LLC, Honolulu, HI. Informational only. Lot coverage maximums and FAR limits vary by zoning district and are subject to amendment — verify against current adopted ROH Chapter 21 text. Last reviewed May 2026.