ADUs in Cottonwood Heights

Most Cottonwood Heights homeowners asking about an ADU are really choosing between two projects. One is a basement or other space inside the house, which the city treats as a permitted use. The other is a separate building in the back yard, which currently needs a conditional use approval from the Planning Commission after a public hearing. The rules, the parking and the time involved differ enough that it pays to know which path you are on before any design work.

On east-side lots near the foothills, the sensitive-lands rules can narrow both paths further.

Where ADUs are allowed

Chapter 19.75, adopted in 2021, allows ADUs in the city's R-1 (single-family), RR-1 (rural residential) and F-1 (foothill residential) zones, on a property with a detached single-family home that the owner lives in. Only one ADU is allowed per lot, and every ADU needs a city ADU license that is renewed each year.

Internal or detached: the two paths

For internal units, see basement ADUs and internal ADUs. For backyard units, see detached ADUs. The code does not define an addition that expands the house as its own ADU type, so how the city would classify one is a question we put to planning staff first.

Property feasibility: what decides it

1. Zone and lot size. R-1, RR-1 or F-1, and more than 6,000 square feet for an internal unit.
2. Rear yard depth. A detached unit must meet the main house's side and rear setbacks, not the smaller setbacks for sheds.
3. Accessory building limits. Accessory buildings may cover no more than 25 percent of the rear yard and, outside the rural residential zones, may not exceed 70 percent of the house's floor area. Staff confirm how the 70 percent rule applies to an ADU.
4. Parking. Can the lot add the stalls without tandem parking and without new front-yard spaces?
5. Slope and sensitive lands. Is any part of the lot steep, near a stream or in the wildland-urban interface?
6. Occupancy. Will the owner live on site at least 200 days a year?

Our feasibility review answers these for one address.

Cottonwood Heights rules and permits

• Owner occupancy: the record owner must live in either the house or the ADU as a permanent residence, at least 200 days per calendar year, and cannot collect rent for the unit they live in. A notarized owner's affidavit is part of the application, and the city's form is set up for recording. See ADU owner occupancy.
• License: the ADU license fee is $100 for either type, with a business license application. It is renewed annually after an inspection.
• Not transferable: a new owner needs an updated ADU permit, inspection if applicable, and a new affidavit.
• Short-term rentals: not allowed in any ADU. See ADU short-term rental rules.
• Lapse: an ADU permit expires if the next approval step is not taken within six months of the last one.

For a detached ADU, the complete application must be in by the prior month's public meeting date to reach the next Planning Commission agenda, and the city's detached checklist says Commission approval comes before the next steps. The city's sources list two different amounts for the detached conditional use fee, so we confirm the current figure with the city.

Lot and site considerations

In the R-1 zones, accessory structures, including detached ADUs, are capped at 20 feet in height, and each foot above 14 feet adds a foot of setback. Height is measured as the average at the four corners from the original natural grade. All enclosed buildings must be at least 6 feet apart. Parking cannot be in tandem, and new parking spaces cannot be created in the front yard beyond existing driveways, which often makes a side or rear parking pad the real constraint for a detached unit. See ADU parking requirements.

On foothill and canyon-edge lots, the sensitive lands chapter applies: no development on slopes over 30 percent, wildland-urban interface construction standards, design review for compatibility with the foothills, and protection within 100 feet of the top of a stream bank. Geologic hazard report review costs are paid by the applicant.

Utility considerations

Separate utility meters for an ADU are prohibited. The city does not provide culinary water: most addresses are served by Salt Lake City Public Utilities and a smaller area by Jordan Valley Water Conservancy District. Cottonwood Improvement District serves portions of the city for sewer, and we confirm the provider by address. Any ADU involving construction needs will-serve letters from the water and sewer providers. See ADU utility connections.

A typical Cottonwood Heights project

1. Pre-application meeting request and a feasibility check.
2. ADU application to planning: narrative, affidavit, business license application, floor plan, parking and access plan, and for detached units a scaled site plan with setbacks, fencing and landscaping.
3. For detached units, the Planning Commission hearing.
4. Online building permit through iWorq, with will-serve letters. The city says it strives to complete a first plan review within 7 business days.
5. Construction, inspection and the ADU license, then annual renewal.

City Hall has been open Monday through Thursday since March 2, 2026, with no inspection requests on Fridays. See ADU permitting.

Cost factors

The detached path adds the conditional use fee, hearing preparation, two parking stalls and a required fence or landscape buffer. Foothill lots can add geotechnical work, wildfire construction standards and design review. Internal units are shaped more by egress, fire separation and bringing the space up to minimum standards. The Utah ADU cost guide explains each driver.

To learn which path fits your lot, See What Your Property Can Support.

Questions from Cottonwood Heights homeowners