San Diego vs. County: Tiny Home Rules Compared (2026)

The Two Legal Paths for Tiny Homes in San Diego

San Diego's sunshine and vibrant lifestyle are a perfect match for the tiny living movement. But if you’re dreaming of parking your tiny home here, you’ve probably discovered it’s not as simple as buying a plot of land. The rules can be confusing, and they change dramatically depending on one key factor: are you in the City of San Diego or the unincorporated areas of San Diego County?

As of 2026, these two jurisdictions offer distinct legal pathways for tiny home dwellers. The City of San Diego paved the way with its Movable Tiny House Ordinance in 2020, while the County made a game-changing move in late 2025, opening up exciting new possibilities. Understanding the differences between these San Diego City vs County tiny home laws is the first step to making your dream a reality.

This guide will break down the key comparisons, from what kind of home you can build to where you can put it. Let’s navigate the regulations together and find the perfect spot for your new home in beautiful San Diego.

Key Differences: Use as a Primary Home vs. an ADU

Perhaps the single most important distinction between the City and County rules is how you can use your tiny home. This choice fundamentally shapes your project, budget, and lifestyle.

City of San Diego: Tiny Homes as Accessory Dwelling Units (ADUs)

In the City of San Diego, a Movable Tiny House (MTH) is legally classified as a type of Accessory Dwelling Unit, or ADU. This means it must be placed on a residential lot that already has a primary home. You cannot buy a vacant lot in the city and make a tiny home your main residence.

This makes MTHs in the city ideal for:

Homeowners looking to add a rental unit for extra income.
Families wanting to create a separate living space for aging parents or adult children.
Adding a guest house or a private home office.

The key takeaway is that an MTH in the city is always accessory to a larger, primary dwelling.

San Diego County: A Path to Primary Residence

Here’s where things get exciting for tiny home purists. Thanks to a landmark Director's Determination in September 2025, the unincorporated areas of San Diego County now recognize qualifying Tiny Homes on Wheels (THOWs) as legal dwellings. This means you can use a tiny home as a primary residence in San Diego County.

This opens the door to possibilities like:

Buying an empty lot in a rural or suburban part of the county and making your THOW the main house.
Using a THOW as an ADU, similar to the city’s rules.
Replacing an older, traditional home with a new, efficient tiny home.

This flexibility makes the County a magnet for those who want to embrace tiny living without being tied to a larger primary structure.

Construction Standards: Why ANSI A119.5 Matters

Not all tiny homes are built the same, and both the City and County have specific construction standards to ensure safety and quality. These certifications are non-negotiable for getting a permit.

City of San Diego: A More Flexible Approach

The city’s Movable Tiny House Ordinance San Diego allows for two different certifications for your tiny home:

NFPA 1192: The standard for recreational vehicles (RVs).
ANSI A119.5: The standard for Park Model RVs, which typically includes more robust, house-like features.

This flexibility gives you a wider range of builders and pre-built models to choose from. However, the home must still meet specific aesthetic requirements, like having double-pane windows and traditional siding—no slide-outs or shiny metal exteriors allowed!

San Diego County: The Gold Standard

The County is much stricter with its San Diego THOW regulations. To be permitted as a dwelling, a THOW must be built and certified to the ANSI A119.5 (Park Model) standard. The NFPA 1192 RV standard is not accepted for permanent housing.

Why the strict requirement? The ANSI A119.5 standard is generally considered closer to a traditional building code, covering more rigorous electrical, plumbing, and structural systems. By mandating this standard, the County ensures that any tiny home intended for permanent residence is built for long-term durability and safety, just like a conventional house.

Fire Safety and Site Requirements: County's Stricter Rules

Given the County's vast rural and wildland-urban interface areas, it’s no surprise its fire safety and site prep rules are more stringent than the City's.

Fire-Hardening in the County

If you plan to place your THOW in the unincorporated County, be prepared for significant fire-hardening requirements. These are designed to protect your home from wildfire and are mandatory.

Exterior Walls: Must be made of non-combustible or ignition-resistant materials like stucco, metal, or fiber-cement board.
Windows: Must be dual-glazed, with at least one pane being tempered glass.
Roofing: A Class A fire-rated roof is required.
Fire Sprinklers: All THOWs must be equipped with a residential fire sprinkler system (though standard ADU exemptions may apply if used as an ADU).

The City of San Diego requires sprinklers only if the primary home has them or if the property is in a Very High Fire Hazard Severity Zone, making the County’s rules universally stricter on this front.

Site Prep and Setbacks

Both jurisdictions require your tiny home to be placed on a paved surface, but the details differ.

The Pad: The County specifies the exact thickness—2 inches of asphalt or 3 inches of cement—and requires bumper guards or curbs to prevent movement. The City simply requires a paved surface for the wheels and jacks.
Setbacks from Structures: The City requires a 10-foot separation between your tiny home and any other structure on the property. The County is a bit more lenient, requiring only a 6-foot separation.
Setbacks from Property Lines: In the City, an MTH must be at least 5 feet from the property line. In the County, if your THOW is the primary dwelling, it must meet the standard front, side, and rear setbacks for that zone, which can be much larger.

Permitting Process and Costs: What to Expect

No matter where you choose to build, you’ll need to go through a formal permitting process. This ensures your project is legal, safe, and properly connected to utilities.

In both the City and County, your tiny home ADU project will require a building permit. The process involves submitting detailed plans, including a site plan showing the location of the home, utility connections, and the paved pad. While it can seem daunting, this process is what transforms your tiny house from a "vehicle" into a legal "home."

The good news? State law has made it easier and cheaper to build ADUs. In most cases, tiny home ADUs are exempt from high-cost Development Impact Fees (DIFs) and Regional Transportation Fees, which can save you tens of thousands of dollars compared to building a new primary home.

Navigating the paperwork can be complex, but you don't have to do it alone. For a detailed walkthrough of the necessary steps, check out our A Step-by-Step Guide to Permitting a Tiny Home ADU.

Which is Right for You? A Quick Decision Guide

So, City or County? Your answer depends on your goals, your property, and your vision for tiny living.

Choose the City of San Diego if:

You already own a home in the city and want to add an ADU for rental income or family.
You prefer a more urban or suburban setting.
You want the flexibility of choosing a builder with either an RV or Park Model certification.
Your property is not in a high-fire-risk zone, potentially saving you on fire-hardening costs.

Choose San Diego County if:

You dream of having a tiny home as your only home on a piece of land.
You are looking for land in more rural, spacious areas like Fallbrook, Ramona, or Julian.
You want to join an established tiny home community, as many are located in the County. You can explore some of them in our post on San Diego's Top Tiny Home Communities.
You are prepared to invest in a high-quality, ANSI A119.5-certified home with robust fire-safety features.

Ultimately, the legal progress in both the City and County is a massive win for the tiny home movement. It provides clear, legal pathways to create affordable, sustainable, and beautiful housing. Ready to take the next step? Explore our tiny home models and see how we can help you build your dream home in San Diego.