By the Utah ADU Builders Editorial Team · Last verified: June 2026
Unincorporated Salt Lake County ADU Guide (2026)
Yes — ADUs are allowed in unincorporated Salt Lake County, but not on every lot and not automatically. Under the county's 2024 ordinance (Chapter 19.15), an internal ADU is allowed on residential lots of at least 6,000 sq ft, and a detached ADU on lots of at least 7,000 sq ft, as long as the primary home or the ADU is owner-occupied and you can meet parking, setback, utility, and permit requirements. The process runs through the Greater Salt Lake Municipal Services District (MSD).
These are Salt Lake County rules, and they apply only if your property is in an unincorporated area — not inside a city or town. That includes Kearns, Magna, Copperton, Emigration Canyon, and White City, which became municipalities in May 2024 and are no longer unincorporated. Confirm your jurisdiction first (the very next section shows you how).
About this guide. Utah ADU Builders is an independent Utah ADU planning, feasibility, and builder-matching resource — not Salt Lake County, a city office, a law firm, a lender, or a licensed contractor. We may earn compensation when homeowners request a feasibility review or are connected with local professionals, and that never changes how we explain the rules, costs, or risks. This is homeowner guidance, not official code, so always confirm the current requirements for your specific parcel.
What we verified (June 2026): The ADU rules on this page come from Salt Lake County's official ADU guidance and Chapter 19.15; Utah's internal-ADU law via the state Office of the Property Rights Ombudsman; the 2024 law (HB 35) that reclassified the former metro townships; and Greater Salt Lake MSD permitting resources. Cost figures are planning estimates from named public 2026 Utah sources (listed at the end), not quotes.
Quick eligibility answer
An ADU (a second, self-contained home on the same lot as a single-family house) can take a few forms. Here's the fast read for unincorporated Salt Lake County:
| Question | Internal ADU | Detached ADU | Why it matters |
|---|---|---|---|
| Property in unincorporated Salt Lake County? | Required | Required | If you're inside a city or town, that municipality's rules apply instead. |
| Eligible zone? | R, A, Forestry, or PC | R, A, Forestry, or PC | Zoning decides whether this page applies to you. |
| Single-family detached home? | Required | Required | Townhomes and PUDs don't qualify under the county's criteria. |
| Minimum lot size? | 6,000 sq ft | 7,000 sq ft (6,000 in PC Zone with approved design) | One of the fastest ways to rule a project in or out. |
| Extra parking? | One on-site space | One on-site space | Parking quietly kills otherwise-good projects. |
| Building permit? | Yes | Yes | No ADU may be built or converted without one. |
| Owner-occupied? | Home or ADU | Home or ADU | Shapes your rental plan and future resale. |
| Short-term rental (Airbnb)? | No — 30+ day rentals only | No — 30+ day rentals only | This is not a nightly-rental path. |
Rules synthesized from Salt Lake County's official ADU guidance and Chapter 19.15. Your specific parcel still controls — see "What we verified" above and the sources at the end.
A quick, no-obligation check that points you to the likely path — internal, detached, conversion, or 'needs review first.'
See what kind of ADU your property may support →First, make sure your property is actually in unincorporated Salt Lake County
A Salt Lake County mailing address does not mean Salt Lake County's ADU rules govern your property. If your home sits inside an incorporated city or town, that municipality's ordinance and permit process control — and local rules are often different from the county's.
"Unincorporated" means land that isn't part of any city or town. In Salt Lake County, that's mostly scattered pockets, islands surrounded by cities, and some foothill or canyon-adjacent areas. Planning, permits, and inspections for these areas are handled by the Greater Salt Lake Municipal Services District (MSD) using the county's code.
One thing most guides get wrong:
On May 1, 2024, a state law (HB 35) converted the county's five former "metro townships" — Copperton, Emigration Canyon, Kearns, Magna, and White City — into municipalities (cities and towns). They are no longer unincorporated. They still receive planning and permitting through the MSD, so the process feels similar, but each is now its own jurisdiction. If you're in one of them, confirm that municipality's specific ADU standards.
Which rulebook applies to you
| If your parcel is in… | Who governs ADUs | Where to look |
|---|---|---|
| A Salt Lake County city or town (Sandy, Cottonwood Heights, Holladay, Herriman, Millcreek, Murray, West Jordan, South Salt Lake, Draper, Salt Lake City, Brighton, etc.) | That municipality's ordinance | That municipality's ADU/planning page |
| Kearns, Magna, Copperton, Emigration Canyon, or White City (former metro townships, now municipalities since May 2024) | The municipality, permitted through the MSD | Confirm that municipality's ADU standards |
| Unincorporated Salt Lake County (islands, foothill/canyon pockets, county-administered land) | Salt Lake County Chapter 19.15, via the MSD | This guide + the county zoning map |
Not sure? Look your address up on the county's Zoning Map Viewer — a reference tool, not a place to submit anything. If it shows a city or town, use that municipality's rules. If it shows unincorporated Salt Lake County / county-administered land, this guide applies.
If you're in a city or town, start with our Salt Lake County ADU Guide or the relevant municipality page instead — you'll save yourself a lot of wasted planning.
Can you build an ADU in unincorporated Salt Lake County?
You may be able to, if your property is in an eligible residential zone, is a single-family detached home, and can meet the county's lot-size, parking, setback, owner-occupancy, utility, and permit requirements. Two rulebooks stack here: state law and county code. Knowing which one you're using changes what you can build.
The state layer
Utah law (through 2021's HB 82) makes an internal ADU — one created within the footprint of an owner-occupied single-family home for long-term rental of 30 days or more — a permitted use in residentially zoned areas, subject to local restrictions and to building, health, and fire codes. Building an internal ADU inside an existing home is not subject to impact fees under state guidance (Utah Code §11-36a-202).
The local layer
Detached ADUs are not guaranteed by state law; they're a local choice. Salt Lake County chose to allow them and set the conditions in Chapter 19.15 (lot size, setbacks, height, foundation, appearance, and more, all below).
Practical translation: an internal or basement unit is usually the lower-friction path, and a detached backyard unit is allowed but carries more site conditions and cost.
Unincorporated Salt Lake County ADU rules at a glance
The county's rules aren't one yes/no answer. They're a stack: zone, home type, lot size, parking, setbacks, height, coverage, owner occupancy, utilities, permit, rental licensing, and no short-term rentals. Here's the whole stack in one place.
| Rule | Internal ADU | Detached ADU |
|---|---|---|
| Eligible zones | Residential — R, A, Forestry, PC | Residential — R, A, Forestry, PC |
| Property type | Single-family detached residence (not a townhome or PUD) | Same |
| Minimum lot size | 6,000 sq ft | 7,000 sq ft (6,000 in PC Zone with approved design) |
| Setbacks | Same as a single-family home in the zone | ≥10 ft from rear property line; ≥6 ft from the main house; side yards depend on zoning and utility easements |
| Height | Not applicable (inside the home) | Up to 20 ft, or match the main home, depending on setbacks |
| Maximum size | Governed by the home's footprint | No fixed floor-area cap in the county's published guidance — size is shaped by lot/rear-yard coverage, setbacks, and the height limit (confirm §19.15 for your zone) |
| Parking | One additional on-site space beyond the home's required parking | Same |
| Owner occupancy | Owner must live in the home or the ADU | Same |
| Number per lot | One ADU per lot; can't be sold or subdivided separately | Same |
| Utilities | No separate meter allowed; water/sewer availability must be confirmed | May be separately metered if the owner receives both bills; water/sewer confirmed |
| Before renting | Record an owner-occupancy affidavit and get a business license | Same |
| Codes & permit | Building permit required; meet building/fire/health codes; written water-provider confirmation before the permit; separate address marker | Same, plus the construction rules below |
Source: Salt Lake County's official ADU guidance and Chapter 19.15. Your specific parcel and zoning district still control. A setback is the required minimum distance between a structure and your property lines.
How big can it actually be?
This surprises people who read Salt Lake City's rules by mistake. Salt Lake City caps detached ADUs at 1,000 sq ft. Salt Lake County's published ADU guidance does not list a fixed floor-area cap. Instead, your buildable size is shaped by your zone's lot- and rear-yard-coverage limits, your setbacks, and the 20-foot height limit. Because that's unusual, confirm the size your specific lot allows — and check the current §19.15 text, not just the summary guidance.
Detached ADU construction rules
If you're building a separate structure, the county also requires it to:
- Sit on a permanent concrete slab (unless it's above a garage) — not on a basement, piers, or a mobile/temporary foundation.
- Stay out of the front yard and corner-lot side yard unless the lot is at least 1 acre and the ADU is at least 30 ft from the front lot line.
- Be set back at least 10 ft from the front face of the main house.
- Include proper roof drainage and stormwater controls, and keep a single-family appearance.
Converted spaces (basement or garage) must meet egress requirements (like window wells) and have adequate heating and ventilation. Internal ADUs, on the other hand, don't require separate HVAC or firewalls.
Internal vs. detached vs. garage conversion — which path fits?
If your priority is the lowest cost and least friction, an internal or basement ADU usually wins. If your priority is privacy and rental appeal, a detached unit is best but costs and conditions run highest. A garage conversion sits in between. Your lot and your goal decide.
| Path | Best for | Planning estimate (2026)* | Advantages | Tradeoffs |
|---|---|---|---|---|
| Internal / basement | Cheapest way in; family housing; testing rental income | ~$60k–$160k | State-law permitted use (still needs a permit); no impact fees on internal units; no new foundation; no separate HVAC/firewall required | Shares the home; no separate meter; often needs egress work |
| Garage conversion | Middle-ground cost using an existing structure | ~$60k–$180k | Reuses walls, roof, and slab; can be faster | You lose the garage; parking, insulation, and egress upgrades add up |
| Detached (backyard/above-garage) | Rental income; privacy; multi-generational living | ~$200k–$400k+ | Most privacy and rental appeal; can be separately metered | Highest cost; setbacks, foundation, and appearance rules; utility trenching |
*Planning estimates as of 2026, not quotes. Your real number depends on size, finish level, and site conditions. See our full Utah ADU Cost Guide for the detailed breakdown.
Find yourself here:
- →Housing a parent or adult child? An internal unit or a modest detached unit near the house; prioritize single-level access and proximity.
- →After rental income? A detached one- or two-bedroom usually commands the most rent — but check the numbers against build cost before you commit.
- →Want the cheapest path? A basement or internal conversion, especially if you already have a finished lower level with proper egress.
A note on prefab and tiny-home-style units:
Some homeowners consider a prefab or tiny-home detached ADU, including options from providers such as Nest Tiny Homes, a design-build partner we work with. That path still has to meet the same Salt Lake County rules — foundation, building code, utilities, parking, setbacks, and permit approval. The unit price is never the full installed cost, and no provider can guarantee county approval or eligibility for your lot. (We may be compensated if you're connected with a partner; it doesn't change what we tell you about the rules.)
What can stop an ADU from being approved?
The most common early blockers are simple: wrong jurisdiction, wrong property type, a lot that's too small, no room for parking, setback or easement conflicts, utility or septic limits, an owner-occupancy conflict, or a plan to run a short-term rental. Catch these before you spend a dollar on design.
Dealbreaker checklist — any of these needs to be solved first:
- The property is inside a city or town, not unincorporated county.
- It's not a single-family detached home (townhome, PUD, or multi-family).
- Lot is under 6,000 sq ft (internal) or under 7,000 sq ft (detached) with no valid PC-Zone exception.
- There's no feasible on-site parking stall for the ADU.
- A detached unit would violate rear/side setbacks or easements, or land in a prohibited front/corner-side-yard location.
- Your water provider won't confirm service, or sewer/septic capacity can't be verified.
- The owner won't live in either the main home or the ADU.
- The plan is a short-term rental (Airbnb/VRBO).
- The plan assumes the ADU can be sold separately (it can't).
- An existing basement/garage unit was built without permits and can't be brought to code.
Yellow flags that call for a closer look before drawings:
An older detached garage, septic instead of sewer, hillside or sensitive land, shared driveways, unusual parcel history, recorded easements, HOA/CC&R restrictions, or prior unpermitted work.
What permits and documents do you need?
Every ADU here needs a building permit before you build or convert, and applications go through the MSD's online permitting portal (City Works). You'll gather a site plan, floor plan, proof of owner occupancy, and written confirmation from your water provider. Approval is never guaranteed — expect a round or two of comments and corrections, which is normal.
The path, in order:
- 1
Confirm jurisdiction and zoning
Are you unincorporated and in an eligible residential zone?
- 2
Choose the likely ADU type
Internal, detached, or conversion.
- 3
Prepare feasibility basics
Parcel address, lot size, home type, zoning, a rough site plan, proposed ADU location, parking, and water/sewer or septic info.
- 4
Confirm utilities
Get the written water-provider letter and check sewer or septic capacity.
- 5
Submit permit documents
Site plan, floor plan, proof of owner occupancy, water-provider confirmation, and construction drawings (plus any engineered or stamped plans your scope requires).
- 6
Respond to review comments
Corrections are routine, not a rejection.
- 7
Build and pass inspections
Meet building, fire, and health codes; add a separate address marker for mail and emergency response.
- 8
Before you rent
Record the owner-occupancy affidavit and get a business license.
How much does an ADU cost in unincorporated Salt Lake County?
The county doesn't set your price — your ADU type and site conditions do. As a 2026 planning range, internal/basement conversions run lowest, detached new builds run highest, and utility work is the biggest hidden swing on rural lots. These are estimates; real pricing needs a property-specific bid.
| ADU type | Planning estimate (2026)* |
|---|---|
| Basement / internal conversion | ~$60k–$160k |
| Garage conversion | ~$60k–$180k |
| Attached addition | ~$150k–$300k |
| Detached new build | ~$200k–$400k+ |
| Typical per square foot | ~$190–$400/sf |
| Utility trenching to a detached unit (water/sewer/power) | ~$5k–$20k, by distance and slope |
*Planning estimates as of 2026, based on our internal planning assumptions plus named public Utah cost sources (listed at the end of this guide) — not quotes. Your quote depends on size, finish, and site conditions.
Internal ADUs skip impact fees
State guidance exempts internal units built inside an existing home. Detached units may still owe fees.
Bigger is often cheaper per square foot
Fixed costs — a kitchen, a bathroom, a foundation, utility connections, and the permit — get spread across more space, so a modestly larger unit can cost only a little more per foot.
"Cheap" ADUs get expensive
Through utility trenching, egress window wells, sewer lateral issues, water-provider requirements, structural upgrades, drainage, and inspection corrections.
For the full type-by-type, line-item breakdown, see our Utah ADU Cost Guide.
How long does the ADU process take?
Honest answer: we don't publish a guaranteed permit-review timeline for unincorporated Salt Lake County, because it depends on your application's completeness, any corrections, and your builder's schedule — and posting a fake number helps no one. A more useful answer is to know the phases and what controls each one.
| Phase | What controls the timing |
|---|---|
| Feasibility | Jurisdiction, zone, lot size, home type, parking, setbacks, utilities |
| Design / plans | ADU type, existing conditions, designer or engineer availability |
| Utility confirmation | Water provider, sewer provider, or septic review |
| Permit review | How complete your application is; comments and corrections |
| Construction | Contractor schedule, weather, site access, utility work, inspections |
| Rental authorization | Business license, recorded affidavit, owner-occupancy documentation |
As a rough planning frame, many Utah ADU projects run several months from design through move-in — but treat that as a range, not a promise, and let your builder and the permit office give you real dates for your project.
Can you rent it? Owner occupancy, licensing, and short-term rentals
Renting an ADU here is not the same as getting permission to run an Airbnb. The county requires owner occupancy, a business license before you rent, a recorded affidavit, and it does not allow short-term rentals.
Owner occupancy
The owner lives in either the main home or the ADU. You can rent one and live in the other; you can't buy the property purely as an investment and rent both under a standard ADU approval. Short exceptions of up to two years may apply for military deployment, medical services, or religious missions.
Before you rent
You'll record an owner-occupancy affidavit and obtain a business license for the rental unit. A future buyer may need to re-establish these.
No short-term rentals
An ADU approval is not a short-term-rental approval. Rentals must be for 30 consecutive days or longer — so don't build this expecting nightly income.
Can you sell the ADU separately?
No. The ADU can't be sold or subdivided apart from the single-family home.
Utilities, meters, water, sewer, and septic
Utilities are one of the biggest feasibility and budget variables, especially on semi-rural lots. The county requires you to confirm water and sewer availability, and the metering rules differ by ADU type.
- Water: You'll need written confirmation from your water provider before a permit is issued — and capacity isn't guaranteed, especially on a private well or a small water company.
- Sewer vs. septic: Some semi-rural, canyon, foothill, or edge-condition properties rely on an onsite septic system rather than municipal sewer. If a new or modified septic system is needed for a second unit, Salt Lake County Health Department review and permitting may apply, and not every site is suitable — a real cost and feasibility factor, not a formality.
- Meters: Under current county guidance, internal ADUs can't have a separate utility meter, while detached ADUs may be separately metered as long as the property owner receives the bills for both units.
- Foothill and canyon lots: Some foothill or canyon parcels fall under Salt Lake County's Foothills and Canyons Overlay Zone (FCOZ) or watershed and steep-slope rules that add review or limits. Don't assume a canyon-mouth lot behaves like a valley lot.
A quick utility gut-check before you budget:
Water availability, sewer lateral or septic capacity, electrical panel capacity, HVAC plan, trenching distance, driveway or hardscape disruption, metering/billing rules, drainage, and inspection access.
Already have an unpermitted basement or garage unit?
Don't assume an existing apartment is legal just because it's been lived in for years. Salt Lake County's ordinance does allow existing non-compliant ADUs to come into compliance by receiving a permit and verifying that the existing work was done to code — but whether your unit can depends on building, fire, health, zoning, utility, and site conditions.
Before a review, gather:
Photos, an existing floor plan, the year built and any remodel history, the utility setup, window and egress details, ceiling heights, whether there's a separate entrance, parking, any prior permits, and rental history.
The Unincorporated Salt Lake County ADU Feasibility Scorecard
Before you pay for drawings or ask a builder for a quote, score your project against the county's biggest feasibility filters. Count your greens, yellows, and reds.
| Question | 🟢 Green | 🟡 Yellow | 🔴 Red |
|---|---|---|---|
| Unincorporated / county-administered? | Confirmed | Unsure | Inside a city or town |
| Home type | Single-family detached | Unclear records | Townhome / PUD / other |
| Zone | R, A, Forestry, or PC | Unknown | Non-eligible zone |
| Lot size | Meets your ADU type's minimum | Close or unclear | Below the minimum |
| Parking | Clear on-site stall | Maybe, with redesign | No feasible stall |
| Detached setbacks | Clear fit | Needs a survey/site plan | Can't meet setbacks/easements |
| Utilities | Provider path looks likely | Needs confirmation | Provider or septic issue likely |
| Use case | Family or long-term rental | Unclear | Short-term rental plan |
| Owner occupancy | Yes | Special situation | No |
| Budget | Fits the likely type | Tight | Unrealistic for the type |
How to read your score:
- Mostly green → you're ready for a feasibility and cost review.
- Several yellows → do the feasibility work before spending on design.
- Any major red → solve the jurisdiction or rule issue first.
- Multiple reds → you're not ready for builder bids yet.
Turn this scorecard into a property-specific answer, then a realistic cost path.
Run your ADU feasibility check →What to do next
The smart next step isn't to hire the first builder or order plans blindly. It's to confirm your jurisdiction, pick the likely ADU type, flag the rule risks, get a realistic budget range, and then request the right kind of local estimate.
- 1Confirm you're in unincorporated Salt Lake County.
- 2Confirm your zone and that your home is single-family detached.
- 3Choose the likely path — internal, detached, or conversion.
- 4Check lot size, parking, setbacks, and utilities.
- 5Estimate a realistic cost range for that path.
- 6Gather photos and basic property facts.
- 7Run the feasibility check, then move to a cost estimate.
- 8Request builder estimates only after the feasibility makes sense.
When you do talk to a builder:
Bring your address, lot size, ADU type, rough budget, intended use, photos, parking plan, and utility/septic info — that's what turns a vague quote into a useful one. Verify any contractor's Utah license yourself through the Utah Department of Commerce (DOPL) Construction Business Registry. We connect homeowners with local professionals, but we don't call our partners "pre-vetted" or "approved" — you should always confirm licensing and references directly.
What we verified
We built this guide from primary and current sources, and we re-check it on a schedule because these rules change. For this update (June 2026) we checked:
- Salt Lake County's official ADU guidance and Chapter 19.15 (eligibility, lot sizes, setbacks, parking, height, owner occupancy, utilities, licensing, and construction standards).
- Utah state internal-ADU law and impact-fee treatment, via the Utah Office of the Property Rights Ombudsman.
- The 2024 change (HB 35) that reclassified the five former Salt Lake County metro townships as municipalities, effective May 1, 2024.
- Greater Salt Lake MSD planning, building, and permitting resources (City Works).
- Salt Lake County Health Department guidance on onsite wastewater/septic review.
- Cost planning ranges from our internal planning assumptions plus named public 2026 Utah cost sources — published here as estimates only.
- Contractor-license verification through the Utah Department of Commerce (DOPL).
We don't publish fake reviews, fake project photos, guaranteed timelines, or promises of rental income or property-value gains. Where a fact could shift — especially costs, timelines, and utility rules — we flag it as an estimate and verify your specifics through the county process.
FAQ
Sources we checked
- Salt Lake County — Accessory Dwelling Units (Office of Regional Development) — eligibility, lot sizes, setbacks, parking, height, owner occupancy, utilities, licensing, construction standards, and the application process.
- Salt Lake County Code, Chapter 19.15 – Accessory Dwelling Units (Title 19).
- Salt Lake County Code, Chapter 19.72 – Foothills and Canyons Overlay Zone (FCOZ) — foothill/canyon overlay review.
- Salt Lake County Health Department — Septic & Onsite Wastewater Systems — onsite wastewater review and site suitability.
- Salt Lake County Zoning Map Viewer — confirm whether a parcel is unincorporated or within a municipality.
- Utah Office of the Property Rights Ombudsman — Accessory Dwellings (ADUs) — state internal-ADU rules and impact-fee treatment.
- Utah Legislature — HB 35 (2024) — reclassification of the former metro townships, effective May 1, 2024.
- Greater Salt Lake Municipal Services District — Planning & Development and Building Services.
- Salt Lake City ADU Handbook — used only for the Salt Lake City detached-ADU size comparison.
- Utah Department of Commerce (DOPL) — Contracting / Construction Business Registry — contractor-license verification.
- Cost ranges are planning estimates as of 2026, based on our internal planning assumptions plus public Utah ADU cost sources (including our own Utah ADU Cost Guide and current 2026 Utah ADU cost guides). They are estimates, not quotes.
This guide is general information for Utah homeowners, not legal, tax, financial, engineering, or contractor-licensing advice, and it doesn't guarantee permit approval, financing, rental income, or property-value increases. Always confirm current rules for your specific parcel.