Big news for the tiny home community: San Diego County has officially recognized Tiny Homes on Wheels (THOWs) as legal dwellings. This means you can now live full-time in a properly built tiny home on wheels—either as your primary residence or as an accessory dwelling unit (ADU) on your property.
The policy, issued September 4, 2025, by the County’s Planning & Development Services, confirms that THOWs meeting specific construction and safety standards qualify as dwellings under the existing Zoning Ordinance. No ordinance changes were needed—just clear guidance on what’s required.
What This Means for You
If you’ve been waiting for a legal path to tiny home living in San Diego County, this is it. A compliant THOW can now be:
- Your primary residence on any lot zoned for single-family dwellings
- An ADU on a property with an existing home
- A permitted dwelling eligible for utility connections
Once permitted, your tiny home is recognized as a legitimate dwelling—not an RV, not a temporary structure.
Key Requirements to Know
The County adopted the ANSI A119.5 standard (the national Park Model standard) as the baseline, with additional fire and safety requirements specific to San Diego. Here’s what your THOW needs:
Size and Structure
- Maximum 430 square feet (interior measurement)
- Maximum height of 16 feet, single story
- Loft space up to 150 sq ft is allowed and doesn’t count as a second story
- No slide-outs or pop-out sections—all walls and roof must be fixed
- R-13 minimum insulation in exterior walls
Fire Safety
- Non-combustible or ignition-resistant exterior walls
- Dual-glazed windows with at least one tempered pane
- Class A fire-rated roofing
- Residential fire sprinklers (unless used as an ADU, which has exemptions)
- Carbon monoxide and smoke detectors
- Direct egress from any loft space
Placement and Setup
- Must sit on a paved pad (2″ asphalt or 3″ concrete minimum)
- Bumper guards or curbs to prevent movement
- Minimum 6 feet from any other structure
- Connected to electric, water, and sewer with proper permits
Registration
- Must remain DMV-registered as a Park Model RV
- Cannot be self-propelled
- Requires ANSI A119.5 certification sticker from an accredited inspection agency
What Doesn’t Change
This policy doesn’t increase density or change zoning. The number of dwellings allowed on your property is still determined by your zoning designation. Your THOW counts toward that limit—it’s not a bonus unit.
If you’re using the THOW as a primary dwelling, standard setback and zoning rules apply. If it’s an ADU, state ADU laws govern parking requirements (generally, none required).
Why This Matters
San Diego County has been proactive about addressing the housing shortage, and this determination opens a more affordable, flexible path to homeownership. A quality tiny home costs a fraction of traditional construction, can be built faster, and offers mobility if your situation changes.
For property owners, it’s a practical way to add housing for family members or generate rental income without the cost and timeline of a conventional ADU build.
Ready to Explore Your Options?
At American Built Tiny Homes, we’ve been building DMV-registered, ANSI/NFPA-certified tiny homes right here in San Diego for years. Our homes are designed to meet these requirements—we’re not scrambling to catch up with the new policy; we’ve been building to these standards all along.
Whether you’re looking for a primary residence, a backyard ADU, or just want to understand what’s possible on your property, we’re here to help.
Call or Text us at 619-509-8495 to talk through your project, or schedule a consultation to visit our facility and see our builds in person.
Download the full Director’s Determination (PDF) — Link to the official County document for those who want the complete details.