Do I Need Title 24 for a Prefab Home?
Yes if it is built to California code. Modular and other factory-built housing is designed to the California Building Standards Code, Part 6 included, and arrives bearing an HCD insignia. A HUD-code manufactured home is the exception, governed by Title 25, and open-framed panel or kit homes are treated as site-built.
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Three tests
- A HUD label? Then it is a manufactured home, covered on manufactured homes and Title 24.
- An HCD insignia? HCD's handbook says each factory-built unit or component bears an Insignia of Approval, orange for units and red for building components, which tells the building official the product was inspected to California requirements. The code matrix includes Part 6.
- Framing you can still see? The handbook excludes open-framed prefabricated construction from factory-built housing, since the local department can inspect it on site. That house gets its own report.
What "in substantial part" means
A house need not arrive whole. The handbook counts closed sub-assemblies such as kitchen, bathroom, laundry, plumbing and mechanical modules as factory-built when their parts cannot be inspected on site without taking them apart. Commercial modulars are outside the definition (see modular buildings).
What changes once it is on your lot
Under Health and Safety Code Section 19981, a city may not demand plans to recheck an insignia-bearing unit's compliance, apart from local land-use matters. But no such unit may be modified before installation without HCD approval, and none during installation without the local enforcement agency's. A change from the approved plans that affects the structural, mechanical, electrical or plumbing systems counts as a modification, so a swapped furnace or water heater is a likely example.
The foundation, utilities and anything outside the approved design are permitted locally, and a later addition is documented like any house. For the ADU case see prefab ADUs, and for wheels tiny homes. Our residential reports cover the site-built parts.
Common Title 24 Questions
- What is Title 24?
- Do I need a Title 24 report?
- How much does a Title 24 report cost?
- How long does a Title 24 report take?
- What is included in a Title 24 report?
- What plans do I need to upload?
Frequently Asked Questions
No. A modular home is factory-built housing built to the California Building Standards Code. A manufactured home is built to the federal HUD code and is governed by Title 25.
Not without approval. Health and Safety Code Section 19981 bars modifying an insignia-bearing unit before installation without HCD approval, and during installation without local agency approval. A change affecting plumbing or mechanical systems is a modification.
Explore Building Permit Questions
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View all Building Permit Questions guides → · Permits and Compliance · Title 24 guide