The Honolulu rule
DPP's Building Permit Requirements page (read 26 October 2026) quotes ROH 18-3.1(a): a permit is required "To erect, construct, enlarge, alter, repair, move, improve, remove, convert or demolish any building or structure". The exemption list has nothing for additions; the closest is "Tool or storage sheds not exceeding 120 square feet as accessories to dwellings."
| Question | Oʻahu answer |
|---|---|
| Instant online permit? | Only if the property and scope qualify and the value of work is "no more than $75,000" (Instant Online Permits); the usual addition ($100,000) is over that |
| Plans | "Any project that does not qualify for Instant Online Permits, requires plans", to DPP's Building Permit Plan Format Checklist |
| Stamped plans | Work on a one-story residence over $180,000; a two-story residence over $162,000; any work in a special management area, flood hazard area or special design district; reinforced concrete or structural steel members |
| Retaining walls | Over 30 inches need a permit; 5 feet or more need plans stamped by an architect, structural or civil engineer |
| Submit | Apply in HNL Build, then upload plans through ePlans from the emailed link |
| Questions | Permit Center 808-768-8220 or 808-768-3126, eplans@honolulu.gov |
The other reviews an addition triggers
DPP lists agencies that may review alongside the building permit. For a house addition the likely ones:
| Reviewer | Why an addition can land there |
|---|---|
| Zoning Plan Review Branch | Land Use Ordinance limits on the lot |
| Wastewater Branch | Sewer availability and adequacy, and work near sewer easements |
| Board of Water Supply | Water use and adequacy |
| Civil Engineering Branch | Drainage, grading, work near streams and drainage easements |
| NPDES Branch | "any ground disturbance work" |
| Department of Health, Wastewater | Lots on septic tanks or leach fields |
| State Historic Preservation | Parcels with a structure 50 or more years old (flagged as an advisory on the parcel) |
Check the parcel's Warnings tab in DPP's property search before design starts; an advisory there is the early warning of a historic review.
What it costs
ROH Table 18-A, with DPP's plan review fee of "twenty percent (20%) of the tentative Building Permit Fee, up to a maximum of $25,000", due when plans are accepted (fee calculator):
| Addition value | Table 18-A formula | Permit fee | With 20% plan review |
|---|---|---|---|
| $70,000 | $286 + $14 per $1,000 | $1,266 | $1,519.20 |
| $100,000 (usual) | $286 + $14 per $1,000 | $1,686 | $2,023.20 |
| $175,000 | $700 + $10 per $1,000 | $2,450 | $2,940 |
Our arithmetic, at the low end, middle and high end of firms' usual addition values. Revised plans after review cost "$200 or 10% of the original building permit fee, whichever is greater".
Who may build it
DCCA says a licensed contractor is required for any project needing a building, electrical or plumbing permit (Hire a Licensed Contractor). An owner may act as owner-builder under HRS 444-2.5 for their own or close family's use: register for the exemption, supervise the work, hire licensed subcontractors and licensed electricians and plumbers, and keep contracts and proof of payment for three years. Selling or leasing within a year of completion is treated as evidence it was built for sale. License classes and the search: Honolulu contractor license lookup.
What 979 Oʻahu addition permits show
| Measure | Oʻahu additions |
|---|---|
| Permits, July 2022 to June 2025 | 979 |
| Firms | 314 |
| Firms with one permit only | 147 (46.8%) |
| Usual filed value | $100,000 |
| Middle half of firms' usual value | $70,000 to $175,000 |
| Closed (permits a year or more old) | 59.3% |
| Usual days from issue to close | 567 |
| 10th / 90th-percentile firm (10+ permits) | 44.7% / 76.5% |
| Busy firms under 70% closed | 13 of 16 |
| Five busiest firms' share | 15.4% |
Additions are slow to close on Oʻahu: the usual one took 567 days, and only 59.3% of permits a year or more old had closed. Among the 16 firms with 10 or more addition permits, 13 closed fewer than 70%. An addition permit left open can hold up a sale or refinance, so make the final inspection and closed permit a condition of the last payment. The trade is fragmented: the five busiest firms hold only 15.4%. Prices: Honolulu addition cost.
See every Oʻahu addition contractor by permits closed →
Related
Compare firms on the Honolulu addition list; counts by month on Honolulu permit statistics. A separate unit instead: Honolulu ADU and ohana pre-check. Smaller jobs: Honolulu remodel permit. National prices: home addition cost; other cities: do I need a permit for a home addition; the choice itself: ADU vs addition. Past permits on a TMK: Honolulu building permit search.
What this does not tell you
DPP's open data ends in June 2025; newer permits are only in HNL Build. Filed values are the applicant's construction estimate. We have no license match for Honolulu firms, so check each on DCCA's search. Which agencies review a given addition depends on the lot; DPP decides.
How we know this
Permit, plan and stamping rules and the agency list are quoted from DPP's Building Permit Requirements and Instant Online Permits pages; the plan review fee from DPP's fee calculator page (ROH 18-6.1); fees from ROH Table 18-A; read 26 October 2026. License and owner-builder rules from DCCA and HRS 444-2.5, read 22 and 23 October 2026. Fee examples are our arithmetic. Counts are City & County of Honolulu building permits classified as additions, July 2022 to June 2025; closed share uses permits a year or more old.
Numbers come from City & County of Honolulu building permits (DPP), data through July 1, 2025. Nobody paid to be on this page and nobody can.
Questions
- Do I need a permit for a home addition in Honolulu?
Yes. ROH 18-3.1(a) requires a DPP building permit to enlarge any building, and the only size exemption on DPP's list is for tool or storage sheds up to 120 square feet. Additions over $75,000 cannot use the instant online permit, so they are submitted with plans through ePlans.
- How much is a permit for a home addition in Honolulu?
ROH Table 18-A charges $286 plus $14 per $1,000 for work valued $50,000.01 to $100,000, and $700 plus $10 per $1,000 from $100,000.01 to $500,000. A $100,000 addition is $1,686, plus a plan review fee of 20%, or $2,023.20 in all (our arithmetic).
- Do addition plans need an architect's stamp in Honolulu?
When work on a one-story house exceeds $180,000 or on a two-story house exceeds $162,000, or the lot is in a special management area, flood hazard area or special design district, or the main structural members are reinforced concrete or steel, DPP requires plans stamped by a licensed professional.
- How long does a home addition permit take in Honolulu?
The permit stays open through construction. In our file the usual Oʻahu addition permit closed 567 days after it was issued, and 59.3% of those a year or more old were closed.
- Is an ohana unit or ADU an addition in Honolulu?
It is permitted separately, with a pre-check and covenant before the building permit. See our Honolulu ADU and ohana pre-check guide for those steps.
Build your own list
Every firm with that kind of permit on record. Pick what you value. The list moves.
Related guides
- Building a casita in Albuquerque: the 750 sq ft limit, rear-yard rule, parking, free plans, and who builds them
- Arlington's 2,500-square-foot rule: when an addition or new house needs a Land Disturbing Activity and stormwater permit
- Do I need a permit for a home addition in Austin? Review time, fees by square foot, and inspections
- Boulder's demolition review for houses over 50 years old: what counts as demolition, the fees, and the 180-day stay
- Do I need an HVAC permit in Wichita? MABCD's mechanical permit, Table K fees and 5,956 permits
- Do I need a plumbing permit in Wichita? MABCD's Table H fees, the homeowner exam and 11,195 permits
For one city
- Building Permit Requirements — Honolulu Department of Planning and Permitting (accessed 2026-10-26)
- Instant Online Building Permits — Honolulu DPP (accessed 2026-10-26)
- Building Permit Fee Calculator — Honolulu DPP (accessed 2026-10-26)
- ROH Chapter 18, Table 18-A: Fees for Permits — Revised Ordinances of Honolulu (accessed 2026-10-26)
- Hire a Licensed Contractor — DCCA Professional and Vocational Licensing (2026-10-22)
- HRS 444-2.5 Owner-builder exemption (2026-10-23)
- HNL Build — Honolulu DPP (2026-10-23)