ADU rules in Cedar Hills

Detached accessory dwelling units are allowed in every residential zone without a conditional use permit: the code reads that "Accessory dwelling units are permitted within all residential zones within the City unless otherwise prohibited by City Code or a development agreement." Only one accessory dwelling unit is allowed per property: "No more than one (1) accessory dwelling unit, whether internal or detached, shall be permitted per lot or parcel." Utah Code 10-21-304, in force since October 1, 2026, requires Cedar Hills to permit detached units on lots of 11,000 square feet or more; the city sets no minimum lot size at all, so the state floor is not a limit here. A detached unit can still be turned down if the house is on a failing septic tank, if the unit would not have adequate access to a required utility service (sanitary sewer, culinary water, electrical or storm water), or if the utility system it must connect to lacks capacity.

An internal accessory dwelling unit (one created within the footprint of the primary dwelling, per the definition in §10-2-1) is allowed in every residential zone and, like a detached unit, is a permitted use rather than a conditional use. The outward appearance of the house may not change from that of a single family home, interior access must be maintained when the unit is inside the main dwelling, and a dedicated entrance may be on any side or rear (front only if it is below grade). No accessory dwelling unit is allowed in a multi-family dwelling or on a lot that cannot satisfy the parking requirement. Utah Code §10-21-303 independently makes internal accessory dwelling units a permitted use in areas zoned primarily for residential use.

Section 10-5-32 sets no floor area limit for an accessory dwelling unit, attached or detached. The only square footage in the section is the 650 square foot line that decides whether a detached unit needs one parking space or two. State law would let Cedar Hills cap a detached unit at the size of the house, but the city did not adopt that option in its July 2026 amendment. The practical limits are one unit per lot, the requirement that the house keep its single family appearance, and the ordinary zone standards for setbacks, height and lot coverage.

The owner must live in either the primary dwelling or the accessory dwelling unit: "No accessory dwelling unit shall be created or occupied unless; the owner of the property resides in either the primary dwelling unit or the accessory dwelling unit." Owner occupancy has to be sworn to up front, because registration requires "an affidavit stating that the dwelling is owner occupied," and the yearly renewal requires evidence that the primary dwelling is owner occupied. Owner means the person on the Utah County tax assessment rolls, or the trustor or trustee if the home sits in a trust (trust documentation goes to the City). Two exceptions exist: a bona fide temporary absence of three years or less (job assignment, sabbatical, voluntary service) with a family member living at the residence and a temporary absence application filed after at least one year of residency, or placement in a hospital, nursing home or assisted living facility with a family member in residence.

The July 2026 amendment replaced the flat two space rule for non-internal units with a size tier: "Two (2) off-street parking spaces shall be assigned to a detached accessory dwelling unit that is 650 square feet or larger. One (1) off-street parking space shall be assigned to a detached accessory dwelling unit that is smaller than 650 square feet." An internal unit still needs one off-street space for tenant parking on top of what the single family home already requires, and no accessory dwelling unit is allowed on a lot that cannot satisfy the parking requirements. Spaces may not sit in a front or side yard except within an approved driveway, and tandem parking in a driveway counts toward the requirement. The published code still prints the old sentence "A minimum of two (2) parking spaces shall be required for all accessory dwellings not internal to the single-family dwelling," but the adopted ordinance struck it, and Utah Code 10-21-304(3)(c) has barred requiring more than one space for a detached unit under 650 square feet since October 1, 2026.

Cedar Hills repealed its accessory dwelling unit conditional use permit on July 7, 2026 to comply with 2026 Senate Bill 284; accessory dwelling units are a permitted use in all residential zones. What remains is registration: "Accessory dwelling units shall be required to submit a registration fee with a completed registration form including a site plan that shows property lines and dimensions, the location of existing buildings and building entrances, proposed additions, location of parking for tenants, and an affidavit stating that the dwelling is owner occupied." A building permit is required before any new construction and a certificate of occupancy or completion before anyone moves in. The registration is good for the year it is issued and renews automatically on the one-time registration fee, evidence of owner occupancy, and a City determination that the conditions of approval still hold; an unregistered unit is not legal and can draw a lien against the property.

An accessory dwelling unit "may only be rented to one family unit as defined by section 10-2-1," which caps an unrelated group at four people living as a single housekeeping unit. The unit "shall not be sold or detached by deed and shall only be rented," so it cannot become a separate property. The registration becomes null and void when the single family dwelling is sold, and the buyer has to apply for a new one. Cedar Hills did not adopt the state's optional 90 day minimum lease for detached units, but any rental shorter than 30 days is a short-term rental under §10-5-41 and needs its own conditional use permit and short-term rental business license.