IBC 2018 in Hawaii: Local Amendments Under ROH Chapter 16 That Affect Your Plans
Honolulu has adopted the International Building Code 2018, but adoption is not the same as identical application. ROH Chapter 16 incorporates local amendments, and Hawaii's distinct climate, seismic environment, and fire code overlay create requirements that diverge materially from the model code in ways that generate plan check comments on otherwise well-prepared submissions.
How the adoption cycle works in Honolulu
The City and County of Honolulu adopts the IBC through ROH Chapter 16, which is updated periodically by City Council action. The current adopted edition is IBC 2018. Honolulu does not automatically update to each new IBC edition when the ICC publishes it — the adoption of a new code edition requires local legislative action.
ROH Chapter 16 incorporates the IBC by reference and then adds local amendments. These amendments can add requirements beyond the model code, delete model code provisions, or substitute different text. When DPP plan checkers cite a code violation, they may be citing the model IBC section as amended by ROH Chapter 16 — the plain IBC text may not be the operative requirement.
Your general notes must cite the correct adopted edition: "International Building Code 2018, as adopted by ROH Chapter 16." General notes that cite IBC 2021 (not yet adopted in Honolulu) or that omit the local adoption reference are technically inaccurate and may draw comments.
In addition to the IBC, Honolulu adopts companion codes: the International Residential Code (IRC) for one- and two-family dwellings, the International Mechanical Code (IMC), the International Plumbing Code (IPC), and the National Electrical Code (NEC) — each through its respective ROH chapter. The fire code is adopted separately through ROH Chapter 20 (Honolulu Fire Code), which is based on the International Fire Code (IFC) with local amendments.
Key local amendments that affect plan submissions
Model IBC: IBC 2018 §903.3.1.3 / NFPA 13D: One- and two-family dwellings and townhouses are subject to IRC sprinkler requirements where the IRC is adopted. Under the model IBC alone, a standalone single-family dwelling is not required to be sprinklered.
Hawaii/Honolulu: ROH Chapter 20 (Fire Code) and Chapter 16 amendments require automatic fire sprinkler systems in new one- and two-family dwellings and townhouses above a specified floor area threshold. The specific threshold has been subject to amendment — verify the current threshold with DPP and the Honolulu Fire Department. Sprinkler requirements also apply to additions above a specified size that trigger substantial improvement thresholds.
Plan check impact: This is the most common source of missed compliance on residential projects. If your general notes say 'non-sprinklered' for a new dwelling above the threshold, the plans will come back with a comment.
Model IBC: IBC 2018 §1613 references ASCE 7-16 for seismic design. The seismic design category is determined by mapped spectral response accelerations from the USGS hazard maps and the site's occupancy category.
Hawaii/Honolulu: Hawaii is in a region of significant seismic activity. Most of Oahu falls in Seismic Design Category C or D depending on soil conditions and occupancy. The site-specific seismic design parameters must be determined from the USGS maps for Hawaii — not defaulted from mainland values. Liquefaction potential and site class are particularly important in coastal and reclaimed land areas.
Plan check impact: General notes that cite seismic design parameters without specifying the site class and mapped spectral values will draw comments. Structural calculations must reference Hawaii-specific ground motion values.
Model IBC: The model IBC/IECC 2018 establishes energy efficiency requirements by climate zone. Hawaii is split across multiple IECC climate zones (Zone 1 for most lowland Hawaii).
Hawaii/Honolulu: Hawaii has adopted its own Hawaii Energy Conservation Code (HECC), which differs from the model IECC in several respects — particularly for residential construction. The HECC has its own trade-off calculation methodologies, fenestration requirements, and insulation minimums calibrated to Hawaii's climate. ResCheck calculations must use the Hawaii climate zone inputs; using mainland defaults will produce a non-compliant result.
Plan check impact: Energy compliance documentation that uses mainland climate zone defaults is a common source of resubmittals. Verify that your ResCheck input matches the HECC requirements and that wall assemblies on the drawings match the ResCheck input.
Model IBC: IBC 2018 Chapter 11 requires accessibility compliance for most commercial occupancies. The model code incorporates ANSI A117.1 by reference.
Hawaii/Honolulu: Hawaii has adopted the Americans with Disabilities Act Accessibility Guidelines (ADAAG) and applies federal ADA requirements to commercial construction. For residential construction, Fair Housing Act requirements apply to multi-family dwellings with 4 or more units. The interaction between ADA (federal), state accessibility law (HRS Chapter 347), and the IBC Chapter 11 requirements means that accessibility compliance may require satisfying multiple standards simultaneously.
Plan check impact: For commercial tenant improvement projects, accessibility review often generates comments on path-of-travel requirements — upgrades to the accessible path from the public right-of-way to the work area, not just the work area itself.
Model IBC: IBC 2018 §1609 references ASCE 7-16 for wind design. Basic wind speed is taken from ASCE 7 wind speed maps.
Hawaii/Honolulu: Hawaii has a distinct wind environment — trade wind exposure is persistent, and some areas are subject to Kona storm and hurricane-level wind events. The design wind speed for Hawaii is higher than mainland values at equivalent geographic positions. ASCE 7 maps include Hawaii-specific wind speed contours. Structures in exposed locations (ridgelines, coastal sites, elevated terrain) may require a higher design wind speed than the mapped value.
Plan check impact: Structural general notes must cite the design wind speed used and the exposure category. Notes that omit the wind speed or use a clearly generic mainland value will be questioned.
What your general notes must cover to avoid comments
DPP plan checkers verify general notes against the project data on the drawings. A well-prepared general notes sheet eliminates a predictable category of first-round comments. At minimum, the general notes for a building permit submission should include:
- Building code edition: International Building Code 2018, as adopted by ROH Chapter 16 (or IRC 2018, as applicable)
- Occupancy classification(s): Per IBC Chapter 3, stated for each portion of the building
- Construction type: Per IBC Chapter 6, stated with both Roman numeral and letter suffix (e.g., Type V-B)
- Sprinkler determination: Sprinklered or non-sprinklered, with code basis cited. If non-sprinklered, the basis for the exemption must be clear.
- Seismic design category and parameters: SDC designation, mapped spectral response accelerations (Ss and S1), site class, and Ie factor
- Design wind speed and exposure category: Per ASCE 7-16 Hawaii maps, with exposure category (B, C, or D) stated
- Energy compliance method: ResCheck (residential) or COMcheck (commercial), with report date and compliance margin
- Accessibility standard: ADA 2010 Standards for Accessible Design (commercial), Fair Housing Act (multi-family residential), as applicable
- Zoning district and LUO compliance: ROH Chapter 21 district designation, permitted use confirmation, and LUO dimensional standards summary
Where Hawaii consistently diverges from mainland practice
Architects licensed in other jurisdictions who practice in Hawaii frequently encounter comments in the same categories. These are the areas where mainland practice assumptions most reliably diverge from Hawaii requirements:
- Sprinklers in residential. Many mainland jurisdictions still exempt small single-family dwellings from sprinkler requirements. Hawaii's fire code does not. Confirm the current threshold before declaring a residential project non-sprinklered.
- Coastal and flood construction. Hawaii's coastline means a large proportion of projects fall within FEMA flood zones (AE, VE, or X-shaded). FEMA flood zone requirements — elevation, flood-proofing, use limitations below BFE — apply in addition to IBC requirements and must be shown on the drawings.
- Climate zone energy defaults. Using Climate Zone 4 or 5 defaults from mainland ResCheck templates in Hawaii (Climate Zone 1) produces non-compliant results. Hawaii's climate zone has different insulation requirements, and some mainland prescriptive assemblies are over-specified (unnecessary and sometimes impractical in Hawaii's climate).
- Termite protection. Hawaii is in a high-termite-risk zone. The IBC/IRC require documentation of subterranean termite protection methods in high-risk areas. This is not discretionary — omitting it from the drawings will generate a comment.
Catch local amendment mismatches before DPP does.
Ikena Permit checks your general notes against ROH Chapter 16 requirements — sprinkler determination, seismic parameters, energy compliance method, and construction type — and flags inconsistencies with your drawings before you submit.
Request early access →Published by Ikena Permit, a DBA of Ikena Design & Build LLC, Honolulu, HI. Informational only. Building code adoption in Honolulu is subject to change by City Council action — verify the current adopted edition with DPP before submission. Last reviewed May 2026.