South Salt Lake ADU Builders: What's Allowed, What It Costs, and Your Smartest First Step
South Salt Lake allows accessory dwelling units (ADUs) — both internal units like a basement apartment and external units like a detached backyard cottage or a garage conversion — in its R1 and RM residential zones, on lots of at least 6,000 square feet. You can have up to two (one internal and one external). Owner-occupancy is required, short-term rentals are not allowed, and realistic all-in costs run roughly $50,000–$400,000+ depending on type. This is for homeowners housing family or earning long-term rent — not for pure investors or very small lots.
If you're comparing South Salt Lake ADU builders, the most useful first move isn't collecting three quotes — it's confirming your lot can support the project you have in mind, because the city's rules decide that before any builder can quote it responsibly. An ADU is a self-contained second home — its own kitchen, bath, and entrance — on the same lot as your house.
Last verified: June 2026.
How Utah ADU Builders works
We're a Utah-focused ADU planning, feasibility, and builder-matching resource — not the City of South Salt Lake, a permit office, a law firm, a lender, an architect, an engineer, or a licensed contractor. We may earn compensation when homeowners request a feasibility review or get connected with local professionals. That does not change how we explain South Salt Lake's rules, costs, or risks. Local rules change, so your project always needs site-specific verification.
What we verified for this page
- South Salt Lake City ADU page and ADU Handbook (zoning, lot standards, ADU types, size, setbacks, parking, owner-occupancy, rental, predevelopment step)
- South Salt Lake Building Permits page (permit requirements and review window)
- Utah state law on internal ADUs (Utah Code § 10-21-303) and the internal-ADU impact-fee exemption (Utah Code § 11-36a-202)
- Utah Division of Professional Licensing (DOPL) for verifying a contractor's license
- Cost figures are aggregated 2025–2026 Utah planning ranges, labeled as estimates — not South Salt Lake quotes
South Salt Lake ADU snapshot
| Question | South Salt Lake answer | Why it matters before you hire anyone |
|---|---|---|
| Are ADUs allowed? | Yes — internal and external ADUs in R1 and RM zones, since Feb 7, 2024 | A builder needs to confirm your zone first |
| How many? | Up to two: one internal and one external per lot | Affects whether a second unit is even possible |
| Minimum lot | 6,000 sq ft, and at least 50 ft measured along the lot's length, front line to rear line | Smaller or oddly shaped lots may not qualify |
| Detached/external size cap | The lesser of 50% of your home's square footage (garage excluded) or 1,000 sq ft | A "1,000 sq ft backyard ADU" may not be allowed if your house is small |
| Owner-occupancy | Required for typical homeowner projects — you or immediate family must live in one unit | You generally can't build and rent out both units as an investment |
| Short-term rental | Not allowed (rentals must be 30+ days) | Rules out Airbnb/nightly income |
| Permits | Predevelopment application first, then a building permit | The city review is a two-step gate, not one |
| Realistic cost | ~$50K–$400K+ depending on type (a planning estimate, not a quote) | Your lot and utilities move this more than anything |
Source: South Salt Lake City ADU page and ADU Handbook.
See whether your property is likely a fit before you spend a dollar on estimates.
Check if your South Salt Lake lot qualifies for an ADU →Can you build an ADU in South Salt Lake?
Yes — if your property sits in South Salt Lake's R1 or RM zone, is at least 6,000 square feet with at least 50 feet measured along the lot's length from the front property line to the rear, and you (or an immediate family member) will live in one of the units. The city began allowing both internal and external ADUs on February 7, 2024, but allowing them isn't the same as your specific lot or plan qualifying.
What decides it: your zone (R1 or RM), your lot size (6,000+ sq ft), the lot's length dimension (at least 50 feet front-to-rear — a narrow or irregular lot can fail this even when it's large enough overall), your occupancy plan (owner or immediate family in one unit), and your use (long-term rental or family housing — not nightly rental). If your goal is nightly rental income, an investment property where you rent both units, or selling the ADU separately someday, South Salt Lake's rules will block that — an ADU there cannot be sold separately from the main house, and rentals must be 30 days or longer. Better to know now than after design fees.
South Salt Lake ADU rules at a glance
South Salt Lake permits one internal ADU (no size limit) and one external ADU per qualifying lot. External units are capped at the lesser of half your home's square footage or 1,000 square feet, max out at two bedrooms and 20 feet tall, sit at least 5 feet from side and rear lines and 10 feet from the house, and can't cover more than half the rear yard. These specifics are the whole game — they decide whether your idea is buildable.
| Rule | South Salt Lake requirement |
|---|---|
| Where allowed | R1 and RM zones only |
| Minimum lot | 6,000 sq ft, and at least 50 ft along the lot's length (front line to rear line) |
| Number of ADUs | One internal and one external per lot |
| Internal ADU size | No maximum (additions must meet your home's bulk rules) |
| Internal ADU bedrooms | No limit |
| External ADU size | Lesser of 50% of primary home (garage excluded) or 1,000 sq ft, whichever is more restrictive |
| External ADU bedrooms | No more than two |
| External ADU height | Same as your home or 20 ft, whichever is lower |
| External setbacks | At least 5 ft side and rear; at least 10 ft from the main house |
| Rear-yard coverage | ADU(s) can't cover more than 50% of the rear yard |
| Parking | One additional on-site space per ADU; for additions/attached and external ADUs, more may be required by bedroom count |
| Owner-occupancy | Required (owner or immediate family in one unit) for typical projects; limited exceptions may apply to some properties |
| Rental period | 30 days or longer; short-term rental prohibited |
| Utility meter | A new separate meter for the ADU isn't allowed |
| Address | No new address — the ADU becomes "Unit B" |
| Egress | Egress (escape) windows required for new and existing construction |
| Separate sale | An ADU can't be subdivided or sold apart from the main house |
Source: South Salt Lake City ADU page and ADU Handbook. A setback is the minimum distance a structure must sit from your property line; a utility hookup is the water, sewer, gas, and electrical connection serving the unit.
South Salt Lake ADU readiness self-check
Run your property through this quick self-check before you talk to builders. It won't replace an official review, but it tells you fast whether you're likely in good shape or likely to hit a wall.
- My property is in an R1 or RM zone.
- My lot is at least 6,000 sq ft.
- My lot is at least 50 ft along its length, front line to rear (not just large, but not pinched or oddly shaped).
- I (or an immediate family member) will live in one of the units.
- My plan is long-term rental or family use, not nightly/Airbnb.
- I know which type I'm after: internal (basement/interior), external (detached/garage), or a conversion.
- If detached, my desired size fits the cap (lesser of 50% of my home or 1,000 sq ft) and I have room for 5 ft/10 ft setbacks without covering more than half the rear yard.
- I have a workable spot for the required parking space(s).
- I have a rough idea where sewer/water runs and that the unit can tie in.
Mostly checked? You're likely a good candidate — a feasibility review can confirm the path and rough cost. Several blanks, especially zoning, lot size, lot shape, parking, or short-term rental plans? Check feasibility before you pay anyone for plans.
Check zoning, type, parking, and permit-risk factors before requesting estimates.
See what kind of ADU your property may support →Why a generic "Salt Lake ADU" page can mislead you
South Salt Lake is its own city with its own code, and the rules genuinely differ from its neighbors. It's actually more flexible than some in one way — it allows up to two ADUs per lot and permits external ADUs by right in R1/RM — but stricter in others, like the "whichever is more restrictive" size cap and owner-occupancy. A page written for Salt Lake City or unincorporated Salt Lake County will get your rules wrong, which is exactly why it's worth checking the South Salt Lake specifics before you build a budget around them.
Which type of ADU fits your South Salt Lake property?
The right type depends on what you already have and what you're trying to accomplish. An internal conversion (basement or interior) usually costs the least and has no size cap; a detached backyard unit gives the most privacy and rent but faces the size cap, setbacks, and rear-yard limit; a garage conversion can be either, depending on whether it stays inside your home's footprint. Match the type to your lot and your goal.
| If your goal is… | Usually look at first | South Salt Lake catch to check |
|---|---|---|
| Lowest-cost, least-disruption space for family | Internal / basement ADU | Egress windows, ceiling height, fire separation, the extra parking space, owner-occupancy |
| Most privacy for a parent or long-term renter | External / detached ADU | 6,000 sq ft lot + 50 ft length, the size cap, 5 ft / 10 ft setbacks, 20 ft height, 50% rear-yard coverage |
| Putting an underused garage to work | Garage conversion | Whether the existing structure can meet ADU setbacks and current building code |
| A predictable, product-style build | Prefab / custom unit | Still must fit the external-ADU envelope, plus site work, foundation, utilities, and crane access |
| Nightly/Airbnb income | None — not a fit here | Short-term rental is prohibited |
What an ADU costs in South Salt Lake
No honest page can quote you a real South Salt Lake price without seeing your lot, utilities, parking, design, and permit path. As planning ranges, basement conversions tend to run lowest and ground-up detached units highest. Treat the numbers below as Utah-wide estimates to budget around — not bids.
| ADU type | Utah planning range (estimate, not a quote) | What moves the number |
|---|---|---|
| Basement / internal | ~$50,000–$120,000 | Egress windows, ceiling height, fire separation, electrical subpanel, plumbing, HVAC, a separate entrance |
| Garage conversion | ~$60,000–$150,000 | Slab and structure condition, insulation, running plumbing and heat, meeting setbacks |
| Attached addition | ~$150,000–$250,000 | Foundation, roofline, tying into the existing home, utility extensions |
| Detached / external | ~$200,000–$400,000+ | New foundation, separate utility trenching, its own roof and siding, site access |
How we built these ranges: they're aggregated from published 2025–2026 Utah ADU builder and cost pages plus national cost data adjusted for the Utah market, and presented as planning estimates — not South Salt Lake bids. Your actual number comes from your lot and design.
That works out to roughly $125–$350+ per square foot in Utah, with the Salt Lake Valley trending toward the higher end. Smaller units often cost more per square foot, because the fixed costs of building — excavation, foundation, utility tie-ins — don't shrink much.
The line items Utah homeowners underestimate
The work underground. Utility and sewer connections and sitework on tight lots are where budgets blow up. On fees, there's an important distinction worth getting right. An impact fee is a one-time fee a city charges new dwellings to fund infrastructure — and under Utah law (§ 11-36a-202), construction of an internal ADU within your existing home is not subject to impact fees. A new external/detached ADU can still trigger them, along with building-permit fees, application fees, and utility connection fees, all of which South Salt Lake's handbook lists among possible ADU costs. Confirm the exact fee treatment for your specific project rather than assuming. And build a 10–15% contingency into any ADU budget; Utah winters delay concrete pours, and older homes hide utility surprises until you dig.
For a full breakdown by type, size, and finish level, see our Utah ADU cost guide.
The South Salt Lake permit path, in plain English
South Salt Lake uses a two-step city process: an ADU Predevelopment application that Planning must process before the Building Department will process a building permit. A separate building permit is then required for any structural change, remodel, or new construction. Knowing this order keeps you from paying for full plans on a project the city would have flagged at step one.
| Step | What happens |
|---|---|
| 1. Feasibility | Confirm zone, lot size and length, ADU type, parking, utilities, and your rental/occupancy plan |
| 2. Predevelopment application | Required before a building permit can be processed — the city-specific step most generic builder pages skip. Submit a complete application; gaps slow everything down |
| 3. Building permit | Requires a licensed general contractor and licensed electrical, mechanical, and plumbing subcontractors, your architect's info, a property-owner affidavit, plans, and a plan-check fee based on the project's valuation |
| 4. Review | The city reviews complete building permit applications within 15 business days, sending comments or revisions by email |
| 5. Construction & inspections | Work can't start until the permit is issued; inspections happen during construction, ending in a Certificate of Occupancy or Completion |
| 6. Rental license | If you'll rent the unit, an annual business license is required |
Source: South Salt Lake City ADU page, ADU Handbook, and Building Permits page.
A note on timing: that 15-business-day window is a review turnaround on complete applications — it's when you'll get comments back, not a promise your ADU is approved or finished. Statewide, a typical Utah ADU runs roughly 6–10 months from design through construction; South Salt Lake's specific processing time varies and is worth pinning down early. As homeowners who've been through it put it, permitting and zoning are usually the slowest part.
Get the project organized before builder conversations get expensive.
Get a South Salt Lake ADU feasibility review →How to choose South Salt Lake ADU builders without getting burned
The builder is the highest-leverage decision in the whole project — a good one prevents tens of thousands in change orders and months of delay. Judge them on ADU-specific experience and city-rule awareness, not the lowest headline number. The strongest builders walk your lot before quoting, because the surprises that wreck budgets show up on-site, not on paper.
Questions a good builder should answer before quoting
- Can they tell you whether your project is internal, external, a garage conversion, or prefab — and what changes for each in South Salt Lake?
- Will they check R1/RM zoning, your lot size and length, setbacks, and parking before pricing?
- Who prepares the site plan, floor plan, and any survey or proof of utility service?
- Will they walk you through the predevelopment step, the building permit, inspections, and the rental license?
- Does their estimate break out design, engineering, permits and fees, utilities, egress, parking, sitework, and a change-order policy — or is it one vague number?
- Is there a clear payment schedule and change-order process in writing?
Verify the license yourself
South Salt Lake's building-permit application asks for the general contractor's and subcontractors' state license numbers. Don't take a website's word for it — look up any contractor through Utah's Division of Professional Licensing (DOPL), and separately check whether an owner-builder or other exemption applies to your situation.
Language worth distrusting on any site
On prefab and custom units
We may have partner relationships, including with Nest Tiny Homes, which by its own materials builds ADUs and tiny homes across Salt Lake County. A prefab or custom-unit path can be worth comparing after feasibility — but it still has to fit South Salt Lake's external-ADU size, setbacks, parking, utilities, and site access. We don't rank any partner as the "best" builder, and we disclose the relationship so you can weigh it.
The honest downsides — and when an ADU is not worth it
An ADU is not automatically a smart project just because South Salt Lake has become more ADU-friendly. On a smaller lot, the "whichever is more restrictive" size cap, the 5-foot setbacks, the 50%-rear-yard-coverage limit, owner-occupancy, and the cost of running utilities can shrink — or sink — a project before design even starts. The upside: a feasibility check is built to surface the obvious blockers early, before you've paid for full plans.
Common reasons a South Salt Lake ADU stalls
- The property isn't in an R1 or RM zone.
- The lot is under 6,000 sq ft or too short/narrow (under 50 ft along its length).
- There's no workable spot for the required on-site parking space.
- The detached unit you want is larger than the size cap allows for your home.
- The plan depends on short-term rental income, which isn't permitted.
- The ownership/occupancy setup doesn't meet the owner-or-family rule.
- Existing sewer/water can be reused in theory, but the age or condition forces upgrades or a separate connection.
- Work gets done without permits — which can become an expensive enforcement and resale problem later. The fear of an unpermitted "ghost" apartment is real; do it on the books.
If you're in one of these spots, the right next step usually isn't three builder quotes — it's a feasibility check to find the path that can actually pass review.
What to have ready before you ask for estimates
You don't need a complete permit packet to start. But estimates get far more accurate when a builder knows your address, ADU type, existing layout, parking, utility situation, budget, and how you'll use the unit. South Salt Lake's predevelopment review looks at exactly these feasibility factors, so getting organized early pays off twice.
Project
- Address
- Desired ADU type
- Main goal (family, long-term rental, aging parent, adult child)
- Budget range
- Target timeline
Property
- Zoning district
- Lot size
- Home's square footage
- Photos of backyard, garage, basement, side yards, driveway, utility areas
- Existing parking; rough location of sewer/water
- Any HOA or recorded covenants
Design / permit
- A rough sketch or floor plan
- Basement or garage measurements
- Ceiling height and egress notes for interior conversions
- A concept size for a detached unit
- Any prior remodel permits — or honest notes about past unpermitted work
- Whether you'll rent and for how long
South Salt Lake's predevelopment step can ask for items like a site plan, floor plans, and proof of utility service depending on your project, and it reviews complete applications — so a builder who plans for those upfront will give you a more honest number.
Get the project organized before builder conversations get expensive.
Start a South Salt Lake ADU feasibility and cost estimate →South Salt Lake ADU FAQ
Sources for the answers above: South Salt Lake City ADU page and ADU Handbook; Utah Code § 10-21-303 and § 11-36a-202.
Ready to check the rules, the realistic cost path, and your builder-readiness before requesting estimates?
Request a Utah ADU feasibility review →Sources we checked
- South Salt Lake City — ADUs: https://sslc.gov/520/ADUs
- South Salt Lake ADU Handbook (Feb 7, 2024): https://sslc.gov/DocumentCenter/View/1961/SSL-ADU-Handbook-02072024
- South Salt Lake City — Building Permits: https://sslc.gov/215/Building-Permits
- Utah Code § 10-21-303 (internal ADUs, municipalities): https://le.utah.gov/xcode/Title10/Chapter21/10-21-S303.html
- Utah Code § 11-36a-202 (internal-ADU impact-fee exemption): https://le.utah.gov/xcode/Title11/Chapter36a/11-36a-S202.html
- Utah DOPL license lookup (verify a contractor): https://secure.utah.gov/llv/search/index.html
- Cost figures: aggregated 2025–2026 Utah ADU builder/cost pages and national cost data adjusted for Utah (planning estimates, not South Salt Lake quotes)
Rules and fees change. We re-verify South Salt Lake's ADU page, handbook, and permit pages — and the Utah statutes above — on a quarterly basis and after each Utah legislative session. Last verified: June 2026.