Cottonwood Contractors Built With Integrity
(801) 461-0300
Service

ADU Construction in the Salt Lake Valley

Detached backyard units, garage conversions and internal ADUs — designed around what your lot and your city will actually allow.

From 1 October 2026 most Utah cities have to permit a detached accessory dwelling unit on any lot of 11,000 square feet or more that already has a house on it. That is a genuine change: for a lot of homeowners in this valley, a backyard unit went from a conversation with the planning counter to something the city has to allow.

It is also work we already do. An internal ADU is a basement finish with a kitchen, a compliant egress and its own entrance. A detached ADU is a small ground-up build — foundation, framing, roof, utilities, finishes — which is general contracting. The law is new; the construction is not.

What the work covers

Scope

Whether your lot qualifies, before anything else

Parcel size against the 11,000 square foot threshold, where the setbacks and easements actually leave room, and whether the buildable area that remains is big enough to be worth building on. This is a short conversation and it saves the long expensive one.

Utilities — the real gate

A city may refuse a detached ADU where sanitary sewer, culinary water, electrical or storm water cannot reach it, or where the existing system has no capacity for it. In practice this stops more projects than any zoning rule, and it is the first thing worth checking rather than the last.

The detached build

Excavation, foundation, framing, roofing, mechanical, electrical and plumbing, insulation and finishes — a small house, built to the same codes as a large one, on a site where the large one is already standing and has to keep working throughout.

Garage and outbuilding conversions

The law requires cities to provide a route for converting a legally built accessory structure into a detached ADU, subject to setbacks and to building, health and fire codes. Where the garage held parking the house needed, expect to replace those spaces on site.

Internal ADUs

A separate unit inside the existing house, almost always the basement: kitchen, bathroom, compliant egress, a separate entrance, and enough separation of heat, power and sound that two households can live above and below each other without friction.

Common questions

ADU Construction FAQs

What exactly changed on 1 October 2026?
Utah Code 10-21-304, enacted by S.B. 284, requires a “specified municipality” to adopt a regulation permitting a detached accessory dwelling unit on any lot or parcel of 11,000 square feet or larger that contains a single-family dwelling, where that dwelling is already a permitted use. A specified municipality is a city of the first through fourth class, or a fifth-class city of 5,000 or more people in a county of the first, second or third class — which covers most of Salt Lake County, but not the smallest places in it. Cities remain free to be more generous and allow detached units on smaller lots.
So can my city still turn one down?
On some grounds, yes. What it may not do is require a conditional use permit for a detached ADU in a primarily residential zone, or demand more than two on-site parking spaces (one, if the unit is under 650 square feet). What it may still do is require the unit to meet setback, height, size and lot-coverage rules, to be designed consistently with the house, and to be no larger than the house. It may require that you live in one of the two units, prohibit more than one ADU on the lot, keep it out of the front yard, bar lettings shorter than 90 consecutive days, and refuse one outright where the utilities cannot reach it or lack the capacity to serve it.
Is my city’s ordinance actually written yet?
Possibly not. The requirement takes effect on 1 October 2026 and councils across the valley are amending their ordinances around that date, so what is adopted in your city this month may not be what was adopted last month. We check the current ordinance for your address before anyone draws anything — and we would rather tell you the rule has not settled yet than quote you against one that has since changed.
Can I convert my detached garage instead of building new?
Often, and the law specifically requires cities to include a process for it: converting a legally constructed accessory structure into a detached ADU, subject to the applicable setback requirements and to building, health and fire codes. The usual catches are foundation and slab condition, insulating a structure never built to be heated, and replacing any parking the house needed that the garage was providing.
Is an internal ADU covered by the same rule?
No. What changed on 1 October 2026 concerns detached units. Internal ADUs — a separate unit inside the existing house — sit under different rules, and they differ in construction too: an internal ADU is a basement finish with a kitchen, an egress that meets code and its own entrance. If you are weighing one against the other, the cost gap is usually large and worth understanding before you pick.
What does an ADU cost?
We are not going to publish a range we cannot stand behind. The honest answer is that an internal conversion and a new detached build are different projects at different scales, and the number turns on utility runs, whether the lot needs excavation, and how the unit is finished. Tell us the address and roughly what you have in mind and we will give you a range we will actually hold to.
Where we work

ADU Construction across the Salt Lake Valley

Salt Lake CitySouth Salt LakeMillcreekHolladayMurrayMidvaleCottonwood HeightsWest Valley CityTaylorsvilleKearnsMagnaCoppertonWest JordanSandyWhite CitySouth JordanRivertonHerrimanDraperBluffdaleEmigration CanyonAltaBrighton
Start a project

Ask us about adus

Five details, and we will call you back the same working day to talk through scope, sequence and a realistic budget range.

In case we cannot reach you by phone.

We reply the same working day. No mailing list, no tracking — what we do with this. Prefer to talk? Call (801) 461-0300.

Start a conversation

Thinking about adus?

Tell us what you have in mind and we will talk through scope, sequence and a realistic budget range before anyone commits to anything.

(801) 461-0300
Call now Email us
Call Get a quote