Utah SB 284: What the New Detached ADU Law Means for Your Property
Utah SB 284 changes where detached accessory dwelling units (DADUs) are allowed across the state. Starting October 1, 2026, qualifying cities must permit a detached ADU on many single-family lots that were previously too small to qualify under local rules. If you own a larger lot in a single-family zone, a backyard home may now be on the table where it wasn't before.
But the law has limits, and not every lot qualifies. This page breaks down exactly what SB 284 does, what it does not do, and how to find out where your specific property stands.
What SB 284 Is
SB 284 is a Utah state law, passed in 2026 and signed March 18, 2026, that sets a statewide baseline for where detached ADUs must be allowed. Its ADU provisions take effect October 1, 2026.
Before SB 284, each city set its own detached-ADU rules, and many set lot-size minimums high enough that most homeowners were excluded. SB 284 establishes a floor: qualifying cities can no longer prohibit detached ADUs on properties that meet the state's criteria.
The goal behind the law is straightforward — expand housing options in Utah by allowing homeowners to add a second, smaller home on lots that can physically support one.
The Key Change
Under SB 284, a qualifying city must allow a detached ADU when a property meets all of these conditions:
- Lot size of 11,000 square feet or larger
- Located in a zone that permits single-family dwellings (SFD)
- Contains a lawfully existing single-family home
- Located in a city required to comply under the law
Effective date: October 1, 2026. The 11,000 sq ft threshold is the heart of the change. In many Utah cities, the previous local minimum was significantly higher — which means a large group of homeowners becomes newly eligible the moment the law takes effect.
What SB 284 Does and Does Not Do
It is easy to read headlines about SB 284 and assume every large lot is automatically cleared to build. That is not how the law works. Understanding the boundaries is the difference between a project that moves forward and one that stalls.
What it does
- Sets a statewide floor requiring qualifying cities to allow detached ADUs on properties that meet the criteria above
- Opens eligibility to many lots that local ordinances previously excluded on size alone
- Creates a clear, predictable starting point for homeowners exploring a backyard home
What it does NOT do
- It does not remove your city's own standards. Cities keep authority over setbacks, height, parking, and design. Meeting the threshold gets you in the door — it does not waive the rest of the code.
- It does not override your HOA. CC&Rs that restrict or prohibit ADUs can still apply.
- It does not override short-term-rental bans. An ADU built under SB 284 is not automatically approved for nightly rental use.
- It does not guarantee your lot physically works. Setbacks, utilities, easements, slope, and access still have to pencil out.
This is why we lead with feasibility, not construction. Qualifying under SB 284 is step one — not the finish line.
Who Is Newly Eligible
The homeowners who benefit most from SB 284 are those whose lots were large enough to build on, but not large enough to qualify under the old local rules.
Lehi is a clear example. Under Lehi's prior detached-ADU standards, the local minimum lot size sat at roughly 14,500 square feet. That left a meaningful gap: homeowners with lots between 11,000 and ~14,500 sq ft had properties that could physically support an ADU but were locked out on size alone.
SB 284 closes that gap. A Lehi homeowner with, say, a 12,000 sq ft lot in a single-family zone — previously excluded — now falls within the statewide eligibility floor.
If your lot is 11,000 sq ft or larger and you assumed you didn't qualify, it's worth re-checking. The rules changed underneath the old assumptions.
Start With a Feasibility Property Screen
Before you spend a dollar on design or engineering, the responsible first step is to confirm your property actually qualifies and can physically support an ADU. That's what our free property screen is for.
We look at your lot size, zoning, existing structure, and the local standards that still apply — then tell you honestly whether it makes sense to move forward. Not every lot qualifies, and we'd rather tell you that up front than after you've invested in plans.
If it does make sense, we can walk you through the full path: property screen → site consultation → feasibility check → a $5,000 permit-ready custom ADU design package → city planning and building approval → construction quote → build → inspections → occupancy.
Frequently Asked Questions About SB 284
What does Utah SB 284 do?
SB 284 sets a statewide baseline requiring qualifying Utah cities to allow detached accessory dwelling units (ADUs) on lots of 11,000 square feet or larger that are in single-family zones and contain a lawfully existing single-family home. Its ADU provisions take effect October 1, 2026.
When does SB 284 take effect?
The ADU provisions of SB 284 take effect October 1, 2026. The bill was passed in 2026 and signed on March 18, 2026.
Does my lot automatically qualify for a detached ADU under SB 284?
Not automatically. Your lot must be 11,000 square feet or larger, sit in a zone that permits single-family dwellings, and contain a lawfully existing single-family home — in a city required to comply. Even then, your city's setbacks, parking, height, and design standards still apply, so a property screen is needed to confirm your specific situation.
Does SB 284 override my HOA rules?
No. SB 284 does not override private homeowners association restrictions. If your HOA's CC&Rs limit or prohibit ADUs, those restrictions can still apply to your property.
Can I use an SB 284 ADU as a short-term rental?
Not automatically. SB 284 does not override local or HOA rules on short-term rentals. If your city or HOA prohibits short-term rentals, an ADU built under the law is still subject to those rules.
What if my lot is smaller than 11,000 square feet?
The 11,000 sq ft threshold is the statewide floor that qualifying cities must honor. Some cities allow ADUs on smaller lots under their own local rules, so a smaller lot isn't necessarily a dead end — it just depends on your city. A property screen will tell you what applies to your address.
Does Your Lot Qualify Under SB 284?
The screen is free, fast, and comes with a straight answer — not a sales pitch.
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