(And Why Ignoring Them Could Delay Your Project for Months)

If you’re planning to build a home, renovate, or add an ADU in Honolulu, 2025 is already shaping up to be a huge year. The Department of Planning & Permitting (DPP) has rolled out several major zoning and building rule changes—all designed to make homes safer, stronger, and more resilient.

But here’s the real headline:

If you don’t understand these new rules before you start planning, you could get stuck with surprise delays, redesign costs, or even a denied permit.

Below is a simple, homeowner-friendly guide to the biggest changes now in effect.

Let’s dive in.

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**1. Shoreline Setback Updates

(Effective July 1, 2024 — Now Fully in Use)

How New Rules May Change Your Buildable Area

Shorelines across Oʻahu are shifting faster than ever, and DPP has updated how setbacks are measured in 2025. These changes affect far more than just Hawaii Kai—they apply to every shoreline community, including:

• Hawai‘i Kai
• Kailua
• Waimānalo
• North Shore
• Wai‘anae Coast
• Kakaʻako / Waikīkī oceanfront
• Any residential lot touching or near the water

What’s new?

Shoreline setbacks are now based on updated erosion rates, which means many lots will see increased setback distances. In some areas, the setback has moved back by dozens of feet. The shoreline setback was previously 40 feet, but it has now been updated to 60 feet plus 70 times the annual erosion rate, up to a maximum setback of 130 feet.

Once your shoreline is officially certified, it will not shift makai (seaward), even if your land later gains sand or appears to extend toward the ocean. The certified shoreline always stays mauka (at the most inland point) recorded at certification.

That means:

• Your buildable area could shrink
• Existing structures near the water may be "non-conforming"
• Future additions could face stricter rules (or need special approval)

Additional shoreline clarification:

If your property has a permitted seawall, the shoreline is measured from the seawall.
If your seawall is unpermitted, the Department of Natural Resources (DLNR) and the City & County of Honolulu must research when it was built before your shoreline can be certified, which can add delays to your permitting timeline.

The big risk

Many homeowners assume their old shoreline certification is still valid. But in 2025:

Any shoreline certification older than 1 year must be redone.

No exceptions.

If your certification expires during planning, your architect may have to redraw your entire site plan—delaying your project for months.

Helpful tools

• O‘ahu Shoreline Change Map (University of Hawai‘i + DPP)
• State of Hawai‘i Sea Level Rise Viewer (PacIOOS)

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**2. New Slope Instability Rules

Hillside Lots Now Face Stricter Safety Standards

If you live on or near a slope—think areas like Hawai‘i Loa Ridge, ‘Aiea Heights, Manoa, Palolo, St. Louis Heights, Makakilo, and much of the Windward side—2025 brings new geotechnical requirements you can’t ignore.

What’s changing?

Honolulu is putting more focus on slope movement and hillside stability. New rules require:

• More detailed geotechnical reports
• Updated soil testing standards
• Stricter retaining wall design requirements
• Drainage plans that handle more runoff

Why now?

Recent heavy rain events have caused slope failures across O‘ahu. The city is tightening safety measures to avoid landslides, property damage, and drainage problems.

What homeowners need to know

If your project is on or near a hillside:

• Expect longer site investigation times
• Budget for more engineering work
• Soil reports do NOT expire. A soils report is only required if there is no existing soils report on record for your property.

The earlier you start geotechnical testing, the smoother your planning process will be.

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**3. Sewer Capacity Limitations

Your Permit Might Be Delayed—Even if Your Plans Are Perfect

This one catches homeowners by surprise more than anything else.

Even if your design meets the zoning rules, the sewer line serving your property must have the capacity to handle your project.

What changed in 2025?

Honolulu has updated capacity thresholds in several neighborhoods—especially older areas with aging infrastructure.

If you’re planning:

• A new home
• A new dwelling (Ohana or ADU)
• Rebuilding a demolished second dwelling

…you may be required to get a Sewer Adequacy Memo or wait for DPP’s verification.

Sewer capacity DOES NOT affect additions or new bathrooms within an existing dwelling.

Why this matters

If sewer capacity is limited in your area, your project may be:

• Delayed
• Modified
• Required to reduce fixture counts
• Put on hold until improvements are made

Some Honolulu neighborhoods already have restrictions in place, including parts of:

• Kaimukī
• Moʻiliʻili
• Kailua
• Mānoa
• Wahiawā
• Older urban Honolulu

If you’re planning an ADU, this is especially important—sewer capacity is one of the top reasons ADUs get delayed.

Additional wastewater requirements

If your sewer lateral runs through a private easement, or if a home sits over a City sewer easement, Wastewater may require a copy of the sewer easement agreement.

In some areas, if the sewer lateral currently comes off of an easement (meaning it runs through a neighbor’s lot or a shared access instead of directly to the street), Wastewater is requiring homeowners to abandon that old lateral and install a brand-new sewer line from their property directly to the public sewer main. This requires civil engineering work and adds cost and time to the permitting process.

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**4. Flood Zone Updates

New Flood Maps Released — Full Implementation Begins in 2026

Flood maps across O‘ahu have been updated again, and many homeowners may now be in different flood risk categories than before.

What’s new?

Some areas are being moved into higher-risk zones due to:

• Sea level rise
• Heavier rain events
• Updated storm data
• Climate modeling

This affects hundreds of properties in:

• Ewa Beach
• Waipahu
• Kāne‘ohe
• Kailua
• Hau‘ula
• Honolulu urban corridor
• North Shore flood plains

Although the new flood maps were released last year, they will not be used for permitting until 2026. The early release was intended to give homeowners time to understand their updated flood designation before the new maps officially take effect.

What this means for your project

If your lot is now in a higher-risk flood zone:

• You may need a new elevation certificate
• Your foundation may require new engineering
• You may need flood vents or breakaway walls
• Your survey and site plan may need updating

For homeowners building close to sea level, these changes can significantly affect design and cost.

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**5. New Energy Efficiency Requirements

Better for the Planet, But Expect a Few More Checkboxes

Honolulu is pushing forward with clean-energy policies, and 2025 brings new rules focused on reducing energy use in new homes and major renovations.

Key updates:

The city has not updated insulation requirements, window standards, or lighting rules for homes. Solar water heating has also been required since 2010.

The most relevant recent updates affecting new dwellings are:

• PV readiness for new homes (required for about four years)
• A new EV charger is now required for new houses

Who is affected?

Any homeowner planning:

• A new home
• An ADU
• An Ohana

What to expect

These updates can change:

• Material choices
• Budget planning
• Permit review steps
• Electrical layouts

The good news: a more energy-efficient home is cheaper to run and more comfortable year-round.

Bottom Line: 2025 Is a Major Turning Point for Honolulu Home Projects

If you’re thinking about building or remodeling in the next 12–18 months, these zoning changes aren’t just “nice to know”—they can make or break your timeline.

Here’s the safest plan:

1. Check your shoreline, slope, sewer, and flood status before designing anything
2. Use updated maps and data—even if you checked last year
3. Get an early consultation with your architect so potential issues are caught before you spend money on plans
4. Start your project as early as possible—More homeowners are submitting projects than ever, so those who start early often enjoy the smoothest, fastest approvals.

Honolulu rules are changing fast, and the homeowners who stay informed will save thousands of dollars and months of frustration.

If you want help checking your lot or understanding how these 2025 rules affect your home, our team at Home Planning Hawaii is here to guide you every step of the way.