Can I build an ADU in South Jordan?

Yes, you can build an ADU in South Jordan, and the city has a defined permit for it. What trips people up is not whether it is allowed. It is the difference between the two kinds of unit, and the fact that state law treats one of them much more favorably than the other.

I get asked this most often by buyers doing the math on a mortgage with a rental unit in it, or by families trying to house a parent. Those are different projects with different answers, so it is worth separating them before you start pricing a remodel.

The two kinds, and why the distinction decides everything

South Jordan’s own ADU material draws the line clearly (South Jordan City, sjc.utah.gov ADU permit checklist, checked October 20, 2026).

An internal ADU sits inside the primary dwelling, so the two read as a single home from the street. It has its own kitchen and bathroom, and it is separated from the main house by a wall, a door, a finished entryway or some other barrier that restricts free flow access between the two. The city’s definition is specific about that last point: an opening that could be finished with a door does not count as separated. It has to actually be closed off.

A guesthouse is a detached ADU with its own kitchen and bathroom. A separate building in the back yard.

The reason to care is state law. Utah Code 10-9a-530 governs internal accessory dwelling units, and it bars a municipality from imposing restrictions based on the size of the internal unit relative to the primary dwelling, the total lot size, the street frontage, or internal connectivity. An internal ADU still has to meet building, health and fire codes. The point is that the usual zoning levers a city would reach for do not apply to it.

A detached guesthouse has no equivalent protection. It is subject to ordinary zoning, setbacks and lot standards. Which means the same property can easily support a legal internal ADU and not support a detached one.

A caveat worth stating plainly: statutes get amended, and the legislature has looked at this area more than once. Confirm the current text before you commit money to a plan built around it.

What South Jordan actually asks you to submit

The permit runs through the city’s General Planning application, and the checklist asks for:

• A site plan identifying the off-street parking assigned to the ADU, plus any exterior work or structures tied to it.
• A floor plan showing the ADU’s area with dimensions and room labels, and the square footage of the primary dwelling.
• Elevations, but only if the project involves exterior modifications.
• Fees, including a staff review fee. A Planning Commission review fee may apply if that review is required.
• A building permit application with its own fees, unless you can show proof of an existing Certificate of Occupancy.

Read the parking line twice, because it is the one that quietly kills projects. The plan has to show where the ADU’s car goes, off the street. On a lot with a two-car driveway and no side access, that can be the whole obstacle.

What the city is not the final word on

Three things sit outside city approval and routinely matter more.

Your HOA. South Jordan has a lot of association-governed subdivisions, including Daybreak, and CC&Rs frequently prohibit separate dwelling units, separate entrances, or rentals under a certain term regardless of what the city allows. City permission is not association permission. Read the recorded CC&Rs for the specific subdivision before you draw a single plan.

Your lender and your insurer. Adding a rental unit changes how a property is underwritten and how it is insured. If you are buying with the ADU income in your qualifying numbers, your lender needs to know the unit’s legal status up front, not after closing.

Whether the existing space is actually convertible. Ceiling height, egress windows, a second heat source, and getting plumbing to a new kitchen are the practical costs. A basement with low headroom and no egress window is a much bigger project than a basement with both.

How this compares to building one in Herriman

Buyers shopping the south valley usually look at more than one city, and the ADU answer is not uniform. The state protection for internal units applies across Utah municipalities, but each city layers its own permit process, parking expectations and fees on top, and the detached-unit rules diverge more sharply. Whether you can build an ADU in Herriman walks through that side, and comparing the two is worth an hour if the ADU is central to your plan.

The broader point: do not assume a rule you read for one Utah city applies to the next one over. This is one of the areas where they genuinely differ.

What I actually see go wrong

The expensive mistake is sequencing. Buyers write an offer on a house because it has a basement apartment, close, and then discover the unit was never permitted. An unpermitted unit is not automatically a disaster, but it is now your problem, and bringing it into compliance can mean egress windows, electrical work and a permit process on a house you already own at a price that assumed the unit was fine.

So: before you write the offer, ask the seller in writing whether the ADU is permitted, and ask the city whether a permit exists for that address. Both answers are obtainable in a day. If the unit is unpermitted, that is a negotiating point and a budget item, not a reason to panic.

The other pattern I see is people treating ADU income as free money. It is a rental business with a tenant in your house, and it changes how the home feels and how you spend your weekends. Some of my clients love it. Some sell within three years. Worth being honest with yourself about which you are.

What to do next

Call South Jordan Planning and Zoning at 801-446-4357 and ask two questions for your specific address: whether a permit exists for any existing unit, and what the parking expectation is for a new one. Then pull the CC&Rs.

If you are weighing a house partly on its ADU potential, the number that matters is what the finished unit does to your monthly position, not what it rents for. I am Kelsey Earl, a Realtor with Keller Williams South Valley and I run that math with clients before they write offers rather than after. Start with what your numbers look like and we can work backward from there.

Note: City requirements here come from South Jordan’s published ADU checklist and the statute reference from Utah Code 10-9a-530, both checked October 20, 2026. Ordinances and statutes change. Confirm with the city and, for anything you are relying on legally, with a Utah attorney.