Can I build an ADU in Herriman?

Call Herriman City first, before you buy the house and before you price the build. Whether you can add an accessory dwelling unit is a city question with a city answer, and it varies by address. It varies by city too, and what South Jordan requires for an ADU is not the same process one city over.

This post is not a summary of the ordinance. Those change, and an out-of-date summary on a real estate site is exactly how someone ends up spending money on a plan they cannot build. What this covers is the order to do things in, and the three gates a plan has to pass.

The three gates

An ADU plan has to clear all three of these, and they are independent of each other.

Gate	Who decides	What refusal looks like
City zoning and ordinance	Herriman City	The use is not allowed at that address, or not in that form
HOA, if there is one	Your association	Allowed by the city, prohibited by your covenants
Lender and appraisal	Your lender	Allowed and built, but the income does not help you qualify

Most people only think about the first one. The second is where plans die quietly, and the third is where the financial case falls apart.

Start with the city, and ask about your address

Zoning is not uniform across a town. What is permitted on one street is not necessarily permitted three streets over, and overlays and subdivision-specific conditions can apply.

So the question to ask is not “does Herriman allow ADUs.” It is “what is allowed at this specific address.” Ask the city directly, ask about exterior changes and parking as well as the unit itself, and ask what has to be permitted.

Ask about the distinction between an internal unit and a detached one, because cities commonly treat those very differently. Converting part of an existing basement is a different proposition from putting a separate structure in the back yard, and the rules, the cost and the permitting path are not the same.

Get the answer before you are under contract if you can. This is a phone call and it does not require the seller’s permission.

The HOA is a separate gate, and it stacks

A city permission and an HOA’s rules are two different systems, and satisfying one does not satisfy the other. The St. George rules are different again, and whether you can build an ADU in St. George covers them.

Herriman has a lot of association-governed neighborhoods, and covenants can restrict separate structures, exterior alterations, parking, and whether a dwelling can be occupied by someone who is not family. Whether homes in Herriman have HOAs covers how common that is here and what the associations typically control.

Get the CC&Rs and the architectural rules in writing, and read them yourself rather than relying on a summary from a neighbor or a seller. If you are buying specifically to build, this belongs in your due diligence period.

What a lender will and will not do with the income

This is the part that catches people financially, and it is worth being blunt about.

A lender is not going to let you qualify on rent you hope to collect from a unit that does not exist yet. Even when a unit does exist and is rented, how the income is treated depends on the loan product, the documentation and the appraisal, and the answer is frequently less generous than buyers assume.

So the rule is: buy the house on the payment you can afford without the ADU. If the unit happens later and it produces income, that is upside. If you buy at the top of your approval on the assumption that a future basement apartment closes the gap, you have taken a real risk on a permission you may not get.

Ask your lender specifically, before you write an offer, how they would treat the income and what they would need to see. Do not assume a signed lease solves it.

Buying a house that already has one

A house marketed as having a basement apartment is a different question from building one, and an easier one in some ways and harder in others.

The thing to establish is whether the existing unit is legal — permitted, inspected and recognized by the city — or whether it is simply a basement with a kitchen in it. Those are very different assets. An unpermitted unit can be a liability rather than a feature, and it can complicate financing, insurance and your eventual resale.

Buying a Herriman house with a basement apartment goes through what to check on an existing unit. This post is about the harder case, which is wanting to add one.

Either way, check the permit record yourself. Call the building department or use their portal and ask what permits have been pulled on the address. A finished basement with no permit attached to it tells you something before you ever write an offer.

The costs people leave out

If the city says yes and the HOA says yes, the budget is still usually bigger than the first estimate.

A separate dwelling needs its own egress, and bedroom egress requirements are a common and genuinely expensive surprise in a basement conversion — window wells and new openings in a foundation are not small items. Then there is the kitchen, the bathroom, the fire separation, the heating and cooling, and quite often an electrical panel that is not sized for a second household. The panel question is the one that most often turns a tidy budget into an untidy one.

Parking is another. Cities commonly have something to say about where the additional vehicles go, and a plan that works architecturally can fail on that alone.

And once it is built and rented, you are a landlord. That is a real job with vacancy, maintenance and tenant screening attached, and the people who do well at it treat it as a business rather than as a passive discount on their mortgage.

Who this is genuinely a good idea for

I am not talking anyone out of this. Done properly it is one of the few ways to make a large suburban house carry some of its own cost, and Herriman’s housing stock is large.

It tends to work well for households who want the flexibility for family — an older parent, an adult child, a return-to-school year — where the rental income is a secondary benefit rather than the whole reason. It works less well for buyers who need the income to make the purchase viable, because that is precisely the case where a refusal at any of the three gates leaves you stuck.

If the broader question is whether to stretch for a larger house at all, whether Herriman suits a household without kids and the townhome versus single-family comparison are both worth reading, because the honest answer is sometimes to buy less house rather than to make a big one pay.

If the plan is to add one later, buy for it

A house that can accommodate an ADU later has some identifiable features: a basement with existing egress or the ability to add it without rebuilding half a foundation wall, a separate entrance or an obvious place to put one, an electrical panel with capacity, and a lot and parking arrangement that suits it.

If this is part of why you are buying, make it part of what you are shopping for, and get the city’s answer on specific addresses while you are still choosing between them. That is much cheaper than falling in love with a house and then finding out.

The order that works

Call Herriman City about the specific address. Read the CC&Rs. Ask your lender how they would treat the income. Price the build with a contractor only after the first three, because a designer working from the wrong assumptions produces a beautiful plan you cannot permit.

I am Kelsey Earl, a Realtor with Keller Williams South Valley, and the version of this conversation I have most often is with a buyer who has already decided the basement apartment is happening and has not yet made the first phone call. The call is free and it is the one that determines everything else.

If you are weighing specific Herriman addresses and want to know which ones realistically support this, get in touch and we will work through them before you write an offer.