By the Utah ADU Builders Editorial Team · Last verified: July 2026
Cottonwood Heights ADU Builders: Costs, Rules & Property Fit
Choosing among Cottonwood Heights ADU builders starts with confirming what your lot can support — because the type you can build, and how hard it is to permit, depends on it. Internal ADUs (a unit inside your home, like a basement apartment) are permitted on lots larger than about 6,000 sq ft; detached backyard units currently need a conditional-use permit but become a permitted use on qualifying lots of 11,000 sq ft or larger on October 1, 2026. In this area, plan on higher-than-average costs due to foothill access, slopes, and HOA considerations on the east bench.
What we verified
We checked this page against primary sources, not blog summaries:
- Cottonwood Heights city ADU page and the city's official internal- and detached-ADU checklists — allowed zones, lot minimums, owner-occupancy, parking, fees, the one-ADU-per-property limit, the separate-meter prohibition, will-serve letters, annual renewal, and the short-term-rental rule.
- Utah Code § 10-21-303 (internal ADUs) and § 11-36a-202 (the impact-fee exemption for internal ADUs).
- Senate Bill 284 (2026) / Utah Code § 10-21-304 — the detached-ADU change effective October 1, 2026.
- Utah Office of the Property Rights Ombudsman — internal-ADU protections and HOA limits.
- Cottonwood Heights building-permit page — the city's stated plan-review windows.
- Our own Utah ADU cost guide and cost methodology — used to build planning ranges, labeled as estimates, not quotes.
Where the city's own documents disagree, we say so and tell you what to confirm. Full source links are at the bottom.
First, the honest starting point: feasibility before quotes
Choosing a Cottonwood Heights ADU builder does not start with collecting quotes. It starts with confirming what your property can actually support. A basement conversion and a backyard cottage are different projects with different rules, price tags, and approval paths — and your lot size, zone, parking, slope, and utilities decide which one is realistic. Get that right first, and every quote you gather afterward becomes comparable and honest.
An ADU (accessory dwelling unit) is a second, self-contained home on the same lot as a single-family house — its own kitchen, bath, and entrance. Cottonwood Heights' ADU materials recognize two types:
- Internal ADU — living space created inside your home's existing footprint, most often a basement apartment.
- Detached ADU — a separate structure in the yard (a backyard cottage, or a unit inside a detached garage).
A garage conversion is treated as an internal or a detached ADU depending on whether the garage is part of the home or a separate building. A new addition built onto the house isn't one of the city's two published ADU categories, so if that's your plan, ask the city to classify it before you design around it.
Here's what your lot size unlocks today and after the new state law takes effect:
| Your lot size | Internal ADU | Detached ADU — now (before Oct 1, 2026) | Detached ADU — on/after Oct 1, 2026 |
|---|---|---|---|
| Under 6,000 sq ft | May not qualify — verify | Conditional-use permit; city discretion | State permitted-use mandate does not apply; city discretion |
| Exactly 6,000 sq ft | City documents conflict — verify | Conditional-use permit + Planning Commission | State mandate does not apply |
| More than 6,000, under 11,000 sq ft | Permitted use | Conditional-use permit + Planning Commission | State mandate does not apply; city's current path still governs |
| 11,000 sq ft or larger | Permitted use | Conditional-use permit + Planning Commission | Permitted use for a qualifying detached ADU — no conditional-use permit |
"Permitted use" means allowed by right, subject to the city's standards and a building permit — it does not mean automatic approval. The exactly-6,000 row reflects a real conflict in the city's own documents, explained below.
Can you build an ADU in Cottonwood Heights right now?
Yes, but the path depends on the type and the parcel. Internal ADUs are a permitted use in the city's R-1 (single-family), RR-1 (rural residential), and F-1 (foothill residential) zones on qualifying lots. Detached ADUs are currently allowed only as a conditional use, meaning they require city review and a public hearing before approval.
The current internal ADU path
An internal ADU — think a basement apartment inside your existing home — is the most straightforward path in Cottonwood Heights. Under the city's current rules it's a permitted use in the R-1, RR-1, and F-1 zones on qualifying lots, with these requirements:
- Owner-occupancy. The property's record owner must live in either the main home or the ADU as their permanent residence, and prove it during the application. ("Owner-occupancy" simply means the owner lives on-site.)
- One ADU per property. You can't add a second ADU to a lot that already has one.
- Parking. Every single-family property already needs two off-street stalls; an internal ADU requires one additional stall, and it can't block the home's required parking. Stacked or "tandem" stalls (one car behind another) don't count.
- No separate utility meter. The city's checklists prohibit separate ADU utility meters.
- No short-term rentals. ADUs cannot be used as short-term rentals (stays under 30 days — the Airbnb/VRBO model). Long-term rental is allowed.
- Codes, safety, and licensing. The unit must meet building, health, and fire codes — the state also requires basics like smoke detectors, GFCI outlets, and egress (escape) windows for sleeping rooms. You'll obtain an ADU license (a $100 fee) that must be renewed each year after an annual inspection, and a building permit. Expect to provide will-serve letters from your water and sewer providers.
One useful state-law point: under Utah law (Utah Code § 11-36a-202), an internal ADU built inside your home's existing footprint is not subject to impact fees — the one-time fees cities charge new construction to help fund infrastructure like roads and utilities. That's a real advantage for basement conversions, but it doesn't extend to a detached unit or an addition.
A lot sitting right at 6,000 sq ft is a genuine gray area — see the conflict note below before you count on it. Sources: Cottonwood Heights ADU page; internal-ADU checklist; Property Rights Ombudsman.
The current detached ADU path
A detached ADU — a backyard cottage or separate structure — is a bigger undertaking today. It's a conditional use, which means it isn't allowed automatically: you request approval, and the Planning Commission reviews it at a public hearing. Current requirements include:
- A pre-application meeting with city planning staff before you apply.
- Parking: two additional off-street stalls beyond the two the home already needs, no tandem stalls, and those stalls cannot be in the front yard.
- A landscaping/fencing buffer between parking areas, the ADU entrance, and neighboring properties (a current checklist requirement).
- A permanent structure that meets your zone's primary-structure setback standards and the accessory-structure height and coverage limits. (A setback is the minimum distance a structure must sit from property lines.) Confirm the exact numbers for your zone and parcel.
- Owner-occupancy, the one-ADU-per-property limit, the no-separate-meter rule, and the no-short-term-rental rule all apply here too.
- Fees currently include a $100 ADU license, a conditional-use permit fee (see the conflict below), and a building permit that varies with the project. Expect to provide will-serve letters, and the ADU license must be renewed annually after an inspection.
A conflict in the city's own documents (verify before you count on it)
The internal-ADU lot minimum. The city's ADU FAQ says internal ADUs are allowed on lots of "6,000 sq. ft. or more," while the city's official internal-ADU checklist says "larger than 6,000 sq. ft." That difference matters for a lot right at 6,000 square feet, because Utah law lets a city prohibit internal ADUs on lots at or below 6,000 square feet. If your lot is near that line, confirm your specific parcel's recorded area and get the city's written position before proceeding.
The detached conditional-use fee. The city's ADU FAQ lists the conditional-use permit fee at $1,100, while the official detached-ADU checklist lists it at $1,200. Confirm the current fee at application — don't treat either number as final.
What changes for detached ADUs on October 1, 2026?
Utah's new detached-ADU law raises the minimum a city must allow — but it does not make detached ADUs automatic. Beginning October 1, 2026, covered cities (including Cottonwood Heights) must allow a detached ADU as a permitted use on a qualifying lot: one that is at least 11,000 square feet and already contains a single-family home, in a zone where single-family homes are a permitted use. For those qualifying lots, the conditional-use hurdle falls away — but a building permit, the city's site standards, and all engineering and utility requirements remain.
This comes from Senate Bill 284 (2026 General Session), which enacted Utah Code § 10-21-304. For a qualifying detached ADU in a primarily residential zone, a covered city cannot require a conditional-use permit and cannot require more than one on-site parking space for a detached unit under 650 square feet (or more than two for a unit 650 square feet or larger). Cottonwood Heights is a "specified municipality" under the statute, so it's covered.
What still applies after October 1, 2026 — this is the part homeowners get wrong
- A building permit is still required, and the unit must meet building, health, and fire codes.
- The city can still enforce objective standards: size, height, lot coverage, setbacks, easements, and design consistency.
- The city can still require owner-occupancy and can still restrict how the unit is rented.
- The city can still require replacement parking if a garage conversion removes the home's required stalls.
- The city can still decline a unit where utility capacity or access isn't adequate.
- The mandate applies to qualifying lots. Smaller lots aren't automatically prohibited — the law doesn't bar a city from allowing detached ADUs below 11,000 sq ft — but the then-current city ordinance governs there, so verify rather than assume today's process carries over unchanged.
If your lot is near 11,000 sq ft, or you're weighing whether to apply before or after October 1, that timing can genuinely change your process — confirm it for your specific parcel.
How much does an ADU cost in Cottonwood Heights?
Plan on a range, not a single number — and expect the Cottonwood Heights area to sit above statewide averages. Our Utah ADU cost guide puts the Sandy/Draper/Cottonwood Heights area at roughly $75,000–$190,000+ for a basement/internal conversion and $220,000–$475,000+ for a detached build — higher than the statewide norm because of hillside access, HOAs, and higher finish expectations on the east bench. These are planning estimates, not bids for your property.
For context, here are the statewide ranges by type from our cost guide. The Cottonwood Heights area typically lands at the higher end of these:
| ADU type | What it is | Statewide planning range (estimate) | Typical cost per sq ft |
|---|---|---|---|
| Internal / basement | A unit inside your home's existing footprint | ~$60,000–$150,000+ | ~$100–$250 |
| Garage conversion | Converting an existing garage to living space | ~$60,000–$175,000+ | ~$125–$275 |
| Detached (site-built) | A separate backyard structure | ~$200,000–$400,000+ | ~$250–$450 |
| Prefab / modular | A factory-built unit set on your lot | ~$150,000–$300,000+ installed | ~$225–$400 |
Per-square-foot cost is only a starting point: a kitchen, a bath, permits, and a utility connection don't shrink just because the unit is small, so smaller ADUs cost more per foot. See how we build these ranges.
On top of construction, budget the city fees and site items separately — a serious estimate never buries them in one lump sum. Cottonwood Heights' fees include a $100 ADU license, a conditional-use permit for detached units (the FAQ says $1,100, the checklist says $1,200 — confirm at application), and a building permit that varies with your construction valuation. Some builders include permits and fees in their number and some don't, so confirm what's included.
Why two Cottonwood Heights quotes can differ by tens of thousands. Much of the city sits in and near the foothills. A sloped or hard-to-access lot can add engineering, a deeper foundation, retaining walls, drainage work, geologic-hazard review, and long utility trenching to a detached build. A basement conversion can climb on egress, moisture, and code upgrades. The "$50,000 surprise" almost always comes from these site, utility, and permit items being left out of an early number — not from finishes.
A note on prefab pricing. A factory unit's advertised package price is not the installed price. Site prep, foundation, delivery and crane, utility hookups (connecting water, sewer, gas, and electrical), permits, and site restoration still apply — and on a tight or sloped lot they add up fast.
An honest word before you spend on plans: An ADU is not automatically a smart project just because Utah has become more ADU-friendly. In Cottonwood Heights, a steep lot, tight parking, or long utility runs can quietly break the math. The right project depends on your lot, city, utilities, budget, and use case. A feasibility check tells you whether it works before you pay for a design or chase quotes.
How should you compare Cottonwood Heights ADU builders?
Compare builders by the project they're equipped to deliver — not by who ranks for the city name or hands you the lowest first number. A basement conversion needs remodel and life-safety experience. A detached unit needs new-construction, site, utility, and permitting capability. A modular project needs one party clearly responsible for the unit, foundation, delivery, installation, utilities, permits, inspections, and warranty. Match the builder to the build, then compare like for like.
What to look for by project type
- Internal / basement: documented legal basement conversions, egress and fire-separation work, and clear ownership of plans, permits, inspections, and license closeout.
- Garage conversion: first, whether it's classified internal or detached, and whether converting removes required parking you'd have to replace; then slab, insulation, utilities, and structural work.
- Site-built detached: new residential construction, survey/site planning, excavation and foundation management, utility coordination, and grading/drainage/retaining on foothill lots.
- Prefab / modular: a written responsibility matrix — who manufactures, delivers, sets, builds the foundation, trenches utilities, pulls the permit, handles inspection corrections, and owns the warranty.
The bid-normalization worksheet
A comparison like "Builder A is $230,000 and Builder B is $190,000" is meaningless if one includes site work, utilities, permits, and restoration and the other doesn't. Ask every builder to price the same line items, and note for each whether it's included, an allowance, or excluded:
| Line item | Builder A | Builder B | Builder C |
|---|---|---|---|
| Design & permit drawings | — | — | — |
| Survey / site plan | — | — | — |
| Structural / civil / geotechnical | — | — | — |
| City applications & permit fees | — | — | — |
| Utility hookups & upgrades | — | — | — |
| Grading / drainage / retaining | — | — | — |
| Foundation | — | — | — |
| Structure or modular unit | — | — | — |
| Mechanical / electrical / plumbing | — | — | — |
| Interior finishes & appliances | — | — | — |
| Parking & driveway / flatwork | — | — | — |
| Landscaping & site restoration | — | — | — |
| Permit corrections / reinspections | — | — | — |
| Allowances (with dollar amounts) | — | — | — |
| Exclusions (who pays instead) | — | — | — |
| Contingency | — | — | — |
| Change-order terms | — | — | — |
| Warranty & closeout | — | — | — |
Fill one column per builder. The lowest total isn't the best bid — the most complete, comparable bid is. This worksheet is useful whether or not you ever contact us.
What can stop an ADU from working on your property?
The real dealbreakers aren't floor plans — they're jurisdiction, zoning, lot size, parking geometry, setbacks and easements, utilities, slope, intended use, and budget. Screen these before you pay for a full design or treat a rough quote as buildable. Here's a checklist you can run today:
- Jurisdiction. Confirm the property is actually inside Cottonwood Heights. A "Salt Lake City, 84121" mailing address doesn't always mean the address falls under Cottonwood Heights' rules.
- Zone. Identify whether you're in R-1, RR-1, or F-1 (the zones where ADUs are addressed).
- Recorded lot size. Confirm your actual lot area, and note whether you're near the ~6,000 (internal) or 11,000 (detached, post–Oct 1) thresholds.
- Owner-occupancy. Are you (or a co-owner) prepared to live on the property?
- One ADU only. Does the lot already have an ADU? You can't add a second.
- Parking. Can you add the required extra stalls (one for internal, two for detached) without tandem stalls, and not in the front yard for a detached unit?
- Placement, setbacks, easements. Is there room to site the unit within your zone's setbacks and coverage limits, off easements?
- Utilities. Are water, sewer, and electrical connections practical? Detached units can't have a separate meter, and long trenching or a service upgrade adds real cost.
- Slope, access, drainage. On foothill lots, can equipment reach the build area? Is retaining or a geologic-hazard review likely?
- Intended use. Long-term housing or rental works; a short-term-rental (Airbnb) plan does not under current rules.
- HOA / recorded restrictions. See the note below — internal-ADU rentals get some protection, but detached construction may still face HOA architectural review.
- Budget with contingency. Does your planning budget fit the project type — with room for site or utility surprises?
If several of these come back uncertain, the honest answer may be "not yet" — better to learn now than after you've paid an architect.
On HOAs. Under Utah's Property Rights Ombudsman guidance, an otherwise-compliant internal ADU rental generally may not be prohibited by a community association's CC&Rs or HOA rule. But detached construction, exterior changes, architectural review, easements, and other recorded restrictions can still require separate analysis for your property. (This isn't legal advice — review your own recorded documents.)
How long do Cottonwood Heights ADU permits and construction take?
There's no honest single total, because an internal conversion, a current detached hearing case, a post–October detached application, plan corrections, utility work, and a builder's schedule all differ. The city publishes review targets for parts of the process — not a guaranteed start-to-finish timeline.
The typical sequence:
Feasibility
Confirm jurisdiction, zone, lot size, ADU type, parking, placement, utilities, and budget.
Pre-application meeting
With city planning (not an approval).
Land-use review
For a detached ADU under the current rules, this includes a Planning Commission public hearing. (After October 1, a qualifying detached ADU skips the conditional-use step.)
Building-permit intake and plan review
Cottonwood Heights' building-permit page describes target windows of roughly 5–7 business days to process and route an application and about 7 business days for a first plan review, with state law allowing up to 14 business days per review. Corrections and special reviews add time. Treat these as processing targets for parts of the process, not a total approval timeline — confirm current windows with the city.
Construction and inspections
Length depends on project type, contractor availability, site work, weather, material lead times, and any change orders.
For a fuller walk-through, see our Utah ADU permit and build timeline guide. Source: Cottonwood Heights building-permit page.
How do you verify an ADU contractor in Utah?
Verify any contractor independently before you sign — including anyone we connect you with. Confirm an active Utah license and appropriate scope through DOPL, verify the contracting entity and insurance, review evidence of comparable permitted work, and require a written scope that assigns responsibility for permits, utilities, corrections, inspections, payment, and warranty.
- License: Use the state's DOPL license lookup to confirm the license is active, the name matches the party you're contracting with, and the classification fits the work. A license is point-in-time — check it close to signing, not from an old screenshot.
- Entity and insurance: Get the legal business name, contracting address, and a current certificate of insurance; ask who will supervise the job and who pulls the permit.
- Comparable work: Ask for similar ADU type and site conditions, on permitted (not just conceptual) projects, with references who can speak to communication, changes, inspections, and closeout.
- Red flags: a large unexplained deposit, no written exclusions, "you don't need a permit," a guaranteed approval or completion date before permits and utilities are resolved, a unit-only prefab price sold as complete, or pressure to sign before any feasibility work.
We are not a law firm and this isn't legal advice — it's the same due diligence any careful Utah homeowner should do.
What to do before you request builder estimates
The lowest-risk order is: feasibility first, then a clear project brief, then comparable estimates. That keeps you from pricing an ADU type your lot, parking, utilities, use case, or budget can't support.
- Confirm the address and jurisdiction.
- Identify your zone and recorded lot size.
- Decide whether you're evaluating under current rules or after October 1, 2026.
- Define the use: family housing, flexible space, or long-term rental.
- Pick the likely project type instead of asking every builder to solve every option.
- Test parking and any garage-replacement effect.
- Screen placement, easements, utilities, slope, and drainage.
- Set a planning budget with contingency.
- Write one project brief (address, current use of the space, ADU type, rough size, intended occupant, parking notes, finish level, budget, known constraints).
- Request estimates using the same bid worksheet above.
- Independently verify license, insurance, references, and contract terms.
- Treat every estimate as conditional until site, design, and permitting assumptions are clear.
Get your Cottonwood Heights ADU feasibility check
You'll get a preliminary feasibility and cost report based on your property, then the option to compare local build paths for the project that's actually viable.
How the check works: the first result is an educational feasibility and cost report generated from your property details. Your address isn't shared with a builder unless you ask to connect. If you request an introduction or estimate, the information you submit may be shared with a participating independent professional who may contact you. See our privacy policy and advertising disclosure for details.
How we verified this guide
Our approach is primary sources first, then transparent cost evidence, then independent contractor verification. Current city rules (zones, lot minimum, owner-occupancy, parking, fees, the one-ADU limit, the separate-meter prohibition, will-serve letters, annual renewal, and the short-term-rental prohibition) come from the Cottonwood Heights ADU page and the city's official internal- and detached-ADU checklists — and where those documents disagree, we flag it rather than pick a number. The internal-ADU framework and impact-fee exemption come from Utah Code § 10-21-303 and § 11-36a-202. The October 1, 2026 detached-ADU change comes from Senate Bill 284 and Utah Code § 10-21-304. Cost figures are planning ranges from our own Utah cost guide and methodology — not bids, not guarantees, and not based on any claimed local project of ours. Because the October 1 change is imminent, we re-check this page around that date against the city's adopted implementation, not just the statute.
Our practical view: the costliest mistakes are the avoidable ones — skipping feasibility, misreading the current-versus-October rules, and comparing quotes that don't cover the same work.
Frequently asked questions
Sources
- Cottonwood Heights — Accessory Dwelling Units (city ADU page): cottonwoodheights.utah.gov/city-services/community-development/accessory-dwelling-units
- Cottonwood Heights — Internal ADU checklist (PDF): cottonwoodheights.utah.gov/home/showpublisheddocument/8114/638418746159170000
- Cottonwood Heights — Detached ADU checklist (PDF): cottonwoodheights.utah.gov/home/showpublisheddocument/8116/638418746526230000
- Cottonwood Heights — Building Permits (plan-review windows): cottonwoodheights.utah.gov/city-services/building-permits
- Utah Office of the Property Rights Ombudsman — ADUs (internal-ADU protections, impact-fee exemption, HOA limits): propertyrights.utah.gov/find-the-law/legal-topics/adu/
- Utah Code § 10-21-303 — Internal accessory dwelling units (municipalities): le.utah.gov
- Utah Senate Bill 284 (2026), enacting Utah Code § 10-21-304 (detached-ADU permitted-use path, effective Oct 1, 2026): le.utah.gov
- Utah ADU Builders — Utah ADU cost guide and cost methodology
- Utah DOPL — License Lookup Verification: secure.utah.gov/llv/search/index.html
Concept and process descriptions on this page are for planning only. Actual design, cost, and approval depend on your site and current local rules. This page does not provide legal, tax, financing, engineering, or contractor-licensing advice. The impact-fee exemption applies to internal ADUs built within an existing single-family home; other fees may still apply.
Related resources
- Can I build an ADU in Utah? Statewide guide · Salt Lake County ADU guide · Utah ADU cost guide
- Utah ADU permit guide · How long does it take to build an ADU? · ADU cost by city in Utah
- Basement ADU guide · Detached ADU guide · Prefab ADU Utah · Detached ADU builders Utah
- Sandy ADU guide · Holladay ADU builders · Draper ADU builders · Midvale ADU guide · Murray ADU builders · South Jordan ADU builders