ADU Rules in Davis County Depend on Who Controls Your Zoning
You can build an ADU in Davis County, but whether you need county or city approval depends on where your property sits. Utah law protects internal ADUs in residential zones, while detached units face stricter local review. Start by confirming your permitting jurisdiction before drawing a single plan.
Can you build an ADU in Davis County, Utah?
Yes, you can build an ADU in Davis County, but the rules that govern your specific project depend on whether your property sits in unincorporated Davis County or inside one of its cities, Bountiful, Layton, Farmington, Kaysville, and the others each run their own planning and permitting departments. Utah state law creates a baseline that protects internal accessory dwelling units in residential zones, but local governments retain meaningful authority over lot size, parking, rentals, and design standards. Knowing which jurisdiction controls your parcel is the first step before you spend a dollar on plans.
Key Takeaways
- Utah state law treats an internal ADU as a permitted use in residentially zoned areas, but local governments may still apply lot-size minimums, parking requirements, owner-occupancy rules, and short-term rental restrictions.
- A Davis County address may fall under county government or an incorporated city, the permitting jurisdiction controls which zoning code, application portal, and fee schedule applies to your project.
- Davis County requires a building permit for any new construction, addition, or accessory structure over 200 square feet, and separately for any work involving gas, electrical, plumbing, or mechanical systems regardless of structure size.
- HOAs generally cannot block a qualifying internal ADU under Utah law, but detached ADUs receive weaker HOA protection and may still be prohibited by governing documents.
- Projects requiring Planning Commission review in unincorporated Davis County must be submitted at least one month before the relevant meeting, a timeline that does not apply to straightforward building-permit applications.
How does Utah state law set the baseline for an ADU in Davis County?
Utah law draws a clear line between two types of units, and that line matters for everything that follows.
Internal ADUs vs. detached ADUs: why the distinction matters
An internal accessory dwelling unit (IADU), a self-contained unit built within the footprint of the primary home, such as a basement apartment or an attached in-law suite, is treated as a permitted use in residentially zoned areas under Utah’s Office of Property Rights guidance on ADUs. That’s a meaningful protection: your local government can regulate an IADU, but it cannot simply ban one in a qualifying residential zone.
A detached ADU, a separate structure in the backyard, a converted garage, a standalone cottage, sits in a different category. The state’s framework gives local governments considerably more room to restrict or even prohibit detached units in certain areas. If you’re planning a backyard casita or a garage conversion, expect a more involved local review.
The state’s ADU guidance lists the types of restrictions local governments may lawfully apply to IADUs: minimum lot size, exterior appearance standards for the primary dwelling, additional on-site parking, replacement parking when a garage is converted, rental licenses, restrictions on rentals shorter than 30 consecutive days, and owner-occupancy requirements in specified circumstances. Your city or county may use some or all of these tools, or none of them. You won’t know until you check the specific jurisdiction.
What the state law does NOT do
State law sets a floor, not a finished product. It does not override your city’s development code, it does not eliminate the need for a building permit, and it does not resolve anything in your HOA’s governing documents. Those three layers, local zoning, building permits, and private covenants, each need their own separate check.
How do you actually get approved to build an ADU in Davis County?
This is where most homeowners get tripped up. The process is not one-size-fits-all across Davis County, it depends on exactly where your property sits.
Step 1: Confirm your permitting jurisdiction
The Davis County Recorder specifically notes that building permits are issued by the governing authority where the property is located. A Bountiful address goes to Bountiful City. A Farmington address goes to Farmington City. Only properties in unincorporated Davis County go through the county’s own Planning Department and Building Permits office.
This matters more than it sounds. Each city maintains its own zoning map, setback requirements, lot-size minimums, parking standards, rental-license process, and application portal. The rules in Kaysville are not the rules in Layton. I’ve worked with clients who assumed a county-level rule applied to their incorporated-city address and lost weeks of planning time on that assumption alone.
Step 2: Check your zoning and land-use code
Once you know your jurisdiction, pull the actual zoning code for your parcel. You’re looking for whether ADUs are permitted outright, permitted with conditions, or require a variance or special exception. For properties in unincorporated Davis County, the county’s Planning Department is the right starting point. For incorporated cities, go directly to that city’s planning department.
If your project requires Planning Commission consideration, a variance, a zoning amendment, or a conditional-use permit, Davis County requires applications to be submitted at least one month before the relevant meeting, by 5:00 p.m. That’s a hard deadline, and missing it by a day means waiting another month.
Step 3: Pull your building permit
A qualifying ADU is not a weekend project you can skip permitting on. Davis County requires a building permit for new construction, home additions, basement finishes, and any accessory structure exceeding 200 square feet. Work involving gas, electrical, mechanical, or plumbing systems requires a permit even on smaller structures. A basement conversion to an ADU will typically involve all of those disciplines.
Permit applications and plans for unincorporated Davis County properties are submitted through the county’s online building-permit application portal, with fees paid under the fee schedule in effect when the application is filed. The specific fee amount depends on the scope of work and the current schedule, confirm it directly with the county or your city before budgeting.
Adding an ADU can also affect your property’s assessed value and future tax picture. If you want context on how that works, my post on what Davis County buyers and sellers should know about property taxes covers the basics.
Step 4: Check your HOA documents
Government approval and HOA approval are two separate conversations. Under Utah’s HOA guidance on ADUs, an HOA generally cannot prohibit an owner from constructing an internal ADU that satisfies applicable government requirements. That protection is real, but it has limits.
Detached ADUs are a different story. An HOA’s governing documents may still prohibit a detached structure, and state law gives HOAs more room to enforce those restrictions. If your project is a backyard cottage or a converted garage, read your CC&Rs carefully before you get attached to the design.
The state’s ADU and HOA guidance identifies zoning and density, structural construction, sanitation and water access, safe egress, and fire-rated separations as the core compliance areas your project needs to satisfy regardless of HOA rules. Government codes and HOA procedures are both real, neither one waives the other.
| ADU Type | State Law Baseline | Local Government Authority | HOA Restriction Power |
|---|---|---|---|
| Internal ADU (IADU) | Permitted use in residential zones | May regulate (lot size, parking, rentals, owner-occupancy) | Generally cannot prohibit if government requirements met |
| Detached ADU | No equivalent statewide entitlement | May restrict or prohibit in certain areas; requires local review | May prohibit per governing documents |
| Garage/Carport Conversion | Treated as detached or internal depending on structure | May require replacement parking; permit required for utility work | Varies by HOA governing documents |
What else should you think through before you break ground?
Short-term rentals and rental licenses
If your plan is to list the ADU on a short-term rental platform, check your jurisdiction’s rules before you finalize the design. Under Utah’s ADU framework, local governments may restrict rentals of fewer than 30 consecutive days. Some Davis County cities have enacted short-term rental ordinances with licensing requirements, caps on units, or outright restrictions in certain zones. A unit that pencils out as a short-term rental may not be legal to operate that way, confirm with your specific city or county before you build for that use case.
Rental licenses are a separate requirement from a building permit. Many jurisdictions require an annual license to operate any rental unit, and the ADU’s certificate of occupancy does not substitute for it.
Inspections and occupancy
A permitted ADU goes through inspections at multiple stages, framing, rough mechanical and electrical, insulation, and final. The unit cannot legally be occupied until the final inspection passes and a certificate of occupancy (or equivalent sign-off) is issued. Skipping permits to save time almost always costs more time and money when the work has to be uncovered, corrected, and re-inspected.
Understanding how each Davis County community approaches density and housing is worth thinking through before you commit to a project. My post on Community Culture as a Buying Factor in Davis County gives some useful context on how different cities approach growth and housing density.
Your specific path, how long it takes, what it costs, and what approvals are required, depends on your parcel, your jurisdiction, and the scope of your project. That’s exactly the kind of question I work through with clients before they commit to a design or a contractor.
If you’re thinking about whether an ADU makes sense for your property from a value or investment standpoint, I’d be glad to walk through what I’m seeing in the market and how buyers are responding to ADU-equipped homes in this area. Reach out and we can talk through your situation.
If you’d like to see what’s available in the area or get a sense of how ADU-equipped properties are priced, start with a map search of current Davis County listings.
Readers who want to see what past clients have said about working with Jared can find reviews on Google and Zillow.
Frequently Asked Questions
Can I build an ADU in Davis County, Utah, or does my city control the rules?
It depends on where your property sits. If you’re in an incorporated city, Bountiful, Layton, Farmington, Kaysville, Syracuse, and others, that city’s planning and building departments control the rules, not Davis County. Only properties in unincorporated Davis County go through the county’s own permitting process. The Davis County Recorder confirms that permits are issued by the governing authority where the property is located, so the first step is always confirming your jurisdiction.
Are internal and detached ADUs treated differently under Utah law?
Yes, and the difference is significant. Utah law treats an internal ADU as a permitted use in residentially zoned areas, meaning local governments can regulate but generally cannot ban them outright. Detached ADUs do not have the same statewide protection, local governments have more authority to restrict or prohibit them, and your HOA may also have the power to block a detached structure under its governing documents. Always check both layers separately.
Do I need a building permit to finish a basement as an ADU in Davis County?
Yes. Davis County requires a building permit for basement finishes, and a basement conversion to a habitable ADU will typically involve electrical, plumbing, mechanical, and egress work, all of which require separate permits and inspections regardless of the structure’s size. Unpermitted ADU work creates problems at resale and can require costly corrections to pass inspection later.
Can I rent out my Davis County ADU as a short-term rental?
Not automatically. Utah law allows local governments to restrict ADU rentals to stays of 30 consecutive days or more, and several Davis County cities have enacted short-term rental ordinances with licensing requirements or restrictions. Whether your ADU can operate as a short-term rental depends on your specific city’s code, confirm with your local planning department before designing the unit around that use.
Can my HOA stop me from building an ADU?
For an internal ADU that meets all applicable government requirements, Utah law generally prevents an HOA from blocking the project. For a detached ADU, the answer is less clear, HOA governing documents may still prohibit detached structures, and state law gives HOAs more room to enforce those restrictions. Review your CC&Rs and, if needed, consult a real estate attorney before committing to a detached design. The Utah Department of Commerce’s HOA and ADU guidance is a useful starting point.
Equal Housing Opportunity. Bryson Real Estate LLC, Principal Broker of Record, licensed by the Utah Division of Real Estate. This article is general information only and is not legal, tax, or financial advice. Confirm permit requirements, fees, and applicable regulations with your city or county planning department, and consult a qualified tax advisor or real estate attorney for guidance specific to your situation.
