ADUs in Holladay: Working From the Current Rules

If you looked into an ADU in Holladay a few years ago and were told you needed half an acre, that answer is out of date. The City Council adopted a new ADU ordinance on November 7, 2024, by unanimous vote, and it removed the old minimum lot size for detached units. Parts of the city's website and some application forms still describe the 2021 rules: the half-acre minimum, a 20 foot height limit and an added setback. That mismatch is the first thing we sort out for any Holladay property.

We work with homeowners in Holladay from the adopted ordinance text, and we confirm open points with Community and Economic Development (CED) before design.

Where the opportunity is in Holladay

Under the 2024 ordinance, ADUs may be established on a parcel with a single-family detached home in all residential zones, as long as the standards are met. They are not allowed with attached multi-family structures. The use table lists ADUs as permitted when accessory to a detached single-family dwelling, and the city says external ADUs can now go on any residential lot with a single-family detached structure.

ADU types Holladay recognizes

• Internal ADU (IADU): inside the home, or, per the city's ADU checklist, within its footprint or conditioned space or sharing a wall with it. Basements and attached additions fall here. Egress windows are required for existing and new construction. See basement ADUs.
• External ADU (EADU): a separate, detached building. See detached ADUs and backyard ADUs.
• Converted accessory building: existing garages and accessory buildings, including non-conforming ones, may be converted with standards. An existing structure larger than the chart allows needs a conditional use permit for the extra footprint. See garage conversion ADUs.

Because a family member can satisfy owner occupancy, Holladay's rules suit in-law ADUs and multigenerational living well.

How big a detached ADU can be

Holladay scales the detached footprint to the lot, using its accessory building chart (13.14.101):

The minimum EADU footprint is 200 square feet. Height is capped at 25 feet above existing grade, which the city says accommodates a pitched roof over a detached garage, and the unit must also meet the city's graduated height standards. The "total footprint" column is the accessory building limit, so on a lot that already has a garage or shed we ask CED how it is counted before sizing the ADU.

Lot and site considerations

Setbacks follow the accessory building rules, but Holladay lets owners reduce them in exchange for features that protect neighbors, never closer than the "no closer than" distance above. Examples from the reduction chart: a single-story structure with walls no higher than 10 feet earns 50 percent; an 8 foot masonry wall earns 50 percent; below-grade living space only earns 100 percent; and coordinating with a neighbor to build adjacent ADUs earns 100 percent. The owner files a signed agreement with CED describing the treatment and resulting setback.

The EADU must also meet the zone's lot coverage limits. The ordinance also sets dark-sky lighting standards for external ADUs, and doors, windows and patios cannot open into a required setback. Properties in a floodplain, fault zone or high liquefaction area need a natural hazard clearance. See ADU setback requirements and ADU design.

Holladay rules and permitting

• Owner occupancy: the owner or an immediate family member must live in the house or the ADU. Occupants of the ADU are limited to a single family, which can include up to four unrelated people.
• Parking: one on-site stall above the base requirement, plus replacement of any garage or carport spaces lost to a conversion. An ADU outside the home's existing footprint follows the bedroom-based parking minimums. The city says a second driveway needs a circular connection with 35 feet between entrances.
• Rentals: if rented, for at least 30 consecutive days, under an annual ADU license. The fee is set in the city's consolidated fee schedule.
• Utilities and address: no separate meters from the main house; the address is the main address plus "Unit B"; no ADU on a property with a failing septic tank.
• Permits: a building permit and certificate of occupancy are required, applied for through the Building Division's iWorQ portal with its building permit checklist and zoning worksheet, plus a notarized property ownership affidavit.

Utility considerations

Holladay lists three water providers (Salt Lake City Public Utilities, Jordan Valley Water Conservancy District and Holliday Water Co.) and two sewer providers (Mt. Olympus Improvement District and Cottonwood Improvement District), without saying which serves where. We identify the providers by address. Where Mt. Olympus provides sewer, its adopted 2026 schedule adds one residential equivalent and one capacity fee for a property with an ADU: $30 per month and a $758 capacity fee in 2026. Other providers' ADU fees we confirm case by case. See ADU sewer and water.

A typical Holladay ADU process

Feasibility against the current ordinance; a lot survey and footprint check; design with any setback reductions planned in; engineering; the building permit with the ownership affidavit and any setback agreement; construction and inspection; then the certificate of occupancy and, if you will rent, the ADU license. Our process explains each stage, and ADU permitting covers how we coordinate the applications.

Cost factors

In Holladay the local drivers include which sewer and water providers serve the lot and their fees, the walls, fencing or construction upgrades used to earn a setback reduction, dark-sky lighting, work to bring an older accessory building up to code, and any hazard reports. Unit type, size and finishes still dominate. See the Utah ADU cost guide.

To get a straight answer for your lot, See What Your Property Can Support.

Questions from Holladay homeowners