What is Appendix Q and why does it matter?

Appendix Q is a section of the International Residential Code created for tiny houses on foundations. Hawaiʻi's State Residential Code adopts Appendix Q with amendments and defines tiny houses as 500 sq ft or less excluding lofts.

Do tiny homes on wheels follow the same rules?

Not always. Tiny homes on wheels can be treated differently than permanent dwellings. The safest compliance path for full-time use is usually a permitted structure on a permanent foundation that meets residential code and zoning requirements.

Building on Big Island

Tiny Homes on Hawaiʻi Island

Q: Are tiny homes legal in Hawaiʻi?

Tiny homes can be legal when they comply with applicable building codes and local zoning. Hawaiʻi's State Residential Code adopts IRC Appendix Q for tiny houses on permanent foundations, with a definition up to 500 sq ft excluding lofts.

A practical guide to legal build paths: foundation builds, building code, permitting, and what to verify before you spend.

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Back to Building on Big Island ADUs

Tiny homes are popular, but the legal path on Hawaiʻi Island is often unclear. Whether you're thinking about a small dwelling on a foundation or something on wheels, the rules here differ from the mainland—and getting it wrong can be costly.

This guide clarifies foundation vs wheels, what Appendix Q means for you, how zoning fits in, and what to verify before you invest. Our goal is to help you avoid costly mistakes and choose a path that actually works for full-time living if that's what you want.

Two different categories: foundation vs wheels

Tiny home on a permanent foundation

Best path for full-time occupancy and utility connections. Treated like a residential structure: plan review, permits, inspections.

Tiny home on wheels

Can trigger different rules than a fixed dwelling. The safest approach is to confirm zoning + permissible use before assuming it can be lived in full-time.

Building code: what Hawaiʻi adopted

State building code signal:

Hawaiʻi's State Residential Code adopts IRC Appendix Q for tiny houses, with amendments. It defines a tiny house as a dwelling of 500 sq ft or less in floor area excluding lofts.

This matters because it provides a recognized code pathway for tiny houses on foundations (stairs/lofts/ceiling heights/egress logic).

Appendix Q adopted: Adopted in its entirety with amendments in Hawaiʻi State Residential Code.
Definition: “Tiny House” = 500 sq ft or less excluding lofts (as amended in the State Residential Code).

Zoning + land use: what you must verify for Big Island

Local reality:

Building code compliance does not automatically make a use legal on a given lot. Zoning and land use rules determine whether an additional dwelling is permitted and under what conditions. The County Planning Department zoning and land-use hub is the starting point for verification.

Confirm zoning district: What uses are permitted on your parcel.
Confirm dwelling allowance: Whether an additional unit is allowed and how it must be permitted.
Confirm setbacks + height + coverage: Site constraints that drive footprint and placement.
Confirm utilities: Water, wastewater, power, access.

Recommended compliance path (if you want to live in it)

For most clients who want a real, durable, financeable build:

Design as a permitted dwelling on a permanent foundation
Use Appendix Q as the tiny-house code pathway where applicable
Align the project with zoning: ADU/ʻohana pathway vs other permitted dwelling use
Permit, inspect, and finish like a normal residential build

How we help

Feasibility + strategy

Zoning + use check
Program sizing + layout guidance
Utilities + site constraints

Design-build execution

Permit coordination
Foundation + structure
Inspection readiness

Start Feasibility

The safest path for a tiny home you plan to live in full-time is usually a permitted dwelling on a permanent foundation. If that's your goal, start with a feasibility check—zoning and site constraints will tell you what's possible before you spend on design.

We're happy to walk through your situation and point you toward the right next step.

Related guides

FAQ

Is a tiny home the same as an ADU?

No. A tiny home is a size concept. An ADU/ʻohana unit is a zoning/land-use pathway. You can build a tiny home as an ADU only if the lot and zoning allow it.

What does Hawaiʻi consider a tiny house in code?

The State Residential Code defines a tiny house as 500 sq ft or less excluding lofts and adopts IRC Appendix Q with amendments.

What's the fastest safe route?

Feasibility first: zoning + site. Then design to code (often Appendix Q) and permit it as a legal dwelling pathway for your parcel.