Inland Empire Tiny Homes: Riverside & San Bernardino County ADUs (2026)
The Inland Empire has big lots, room to grow and lots of rural land. Unincorporated Riverside and San Bernardino Counties each have their own ADU rules. Here's a simple side-by-side.
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Side by Side
Riverside County | San Bernardino County | |
ADUs on residential lots | Yes | Yes |
Manufactured home as ADU | Yes, an ADU may be a manufactured home | Yes, an ADU may include a manufactured home |
Pre-approved plans | Permit Ready ADU program | 3 pre-approved detached plans |
Permit decision | State 60-day rule | Within 60 days of a complete application |
San Bernardino County
The County's ADU handout and ADU FAQ say:
On single-family lots under 5 acres, you can add two of: an ADU, a junior ADU or a guest house. Lots of 5 acres or more can add three.
Using a pre-approved plan can shorten approval by up to 30 days.
Projects must connect to sewer when the nearest property line is within 200 feet of a sewer line; otherwise a septic system is needed.
New or separate utility connections may be required.
Riverside County
Riverside County's Additional Residential Accommodations page says an ADU may be an efficiency unit or a manufactured home, and an ADU doesn't count toward the lot's density. The County has a Permit Ready ADU program, and a proposed update would reorganize its ADU rules and treat manufactured homes like other one-family homes.
Cities Have Their Own Rules
Riverside, San Bernardino, Ontario, Fontana and the other cities set their own ADU rules. Near the desert? See Palm Springs & Coachella Valley Tiny Homes. Rules vary by property; our site assessment checks what fits your lot.
Related Guides
Frequently Asked Questions
How long does an ADU permit take in San Bernardino County?
The County says it confirms whether an application is complete within 15 business days and approves or denies a complete ADU permit within 60 days.
How many units can I add in San Bernardino County?
On a single-family lot under 5 acres, you can add two of these: an ADU, a junior ADU or a guest house. Lots of 5 acres or more can add three. Only one junior ADU is allowed.
Is Riverside County changing its ADU rules?
Yes. A proposed update (Change of Zone No. 2600012) would reorganize the County's ADU rules and apply the same standards to manufactured homes as other homes.
Floor Plan Preview
Here's a look at two of the designs Zen Tiny Homes can build. Every plan can be adjusted to fit your lot.
Ranch House: 3D exterior
Grove House: 3D render
See all the layouts in California Tiny Home Floor Plans.
Ready for an Inland Empire Tiny Home?
Big lots bring big options. Our $500 site assessment checks what fits your lot.
Prefer to talk? Call Zen Tiny Homes at 760-492-0742 or visit zentinyhomes.com.
This guide is general information, not legal advice. Rules change and vary by property. Zen's $500 site assessment checks what fits your lot, or call 760-492-0742.
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