In 2021, the Utah legislature passed HB 82. It quietly changed what's possible for homeowners across the state. If you've been wondering whether you can legally add a basement apartment to your Utah house, the short answer is: in almost every case, yes — and that's because of HB 82.
Here's the plain-English version. Three things to know.
1. Internal ADUs are now a "permitted use"
Before HB 82, lots of Utah cities treated ADUs as a conditional use. That meant you had to apply, go through a public hearing, get neighbor input, and hope the planning commission was in a good mood. Many proposals got denied for reasons that had nothing to do with the actual project.
HB 82 changed that. An internal ADU — meaning a separate dwelling unit inside the existing footprint of your single-family home, like a basement apartment or upstairs unit — is now a "permitted use" in any single-family residential zone in Utah. Permitted use means you don't go through a hearing. You apply for a building permit, the city checks the code, and if you meet the code they have to issue the permit.
2. Cities can still impose reasonable requirements
HB 82 didn't make ADUs unregulated. Cities can still require:
- A building permit (always)
- Compliance with the building code (snow load, seismic, fire separation, egress)
- One additional off-street parking space
- Owner-occupancy of either the main unit or the ADU
- Setbacks, height limits, and design standards that apply to single-family homes
- Prohibition of short-term rental (some cities do this; Layton is one)
Cities are also allowed to exclude up to 25% of their residential zones from the rule. So in theory a city could carve out a quarter of its residential land where internal ADUs aren't allowed. In practice, very few cities have used that power aggressively.
3. Attached and detached ADUs are still local-ordinance
HB 82 specifically applies to internal ADUs. It doesn't force cities to allow attached or detached units. Those are still governed by local ordinance, and the rules vary city by city:
- Some cities allow detached ADUs almost as freely as internal — Ogden is historically more permissive.
- Some allow them with stricter setback and lot-coverage rules — Kaysville and Farmington fall here for most lots.
- Some restrict them or require conditional use approval.
We've put together city-by-city cheat sheets for Davis County and Weber County that show the relevant rules for each major city in northern Utah.
What this means in practice
If you want to add an apartment inside your existing home — finishing a basement, converting an unused upstairs, or carving out a separate-entry suite — HB 82 makes that legally permissible in nearly every Utah city, full stop. You'll need a building permit, you'll need stamped structural plans for any meaningful framing or opening changes, and you'll need to meet the building code. But you don't need a zoning hearing and you can't be denied just because the neighbors don't like it.
If you want to add a detached unit (a casita, granny flat, or cottage in the back yard), the answer depends on your city's ordinance. We can help you figure out what's allowed before you commit.
The structural side of an ADU
Almost every ADU we work on needs a stamped structural plan set. The reasons:
- New openings (doors, windows) need engineered headers
- Existing walls may need new shear wall configurations to handle the modified load path
- Garage conversions need evaluation of whether the existing slab and frame can take residential occupancy
- Basement ADUs may need egress window cuts, which are header design problems
- Detached ADUs are essentially small new structures — they need full structural design just like any small custom home
See our ADU services page for the full scope and typical fees, or send us your situation and we'll come back same day with a fixed quote.