ADU rules in Sandy

Since Ordinance 26-55 (adopted September 15, 2026, effective on publication September 21, 2026) Sandy allows a detached ADU on a lot of at least 11,000 square feet in its single-family residential zones; before that, detached units were prohibited. The unit must sit in the rear or side yard behind the front plane of the house (a front-yard location is possible on lots of 40,000 square feet or more that meet the house's setbacks), on a permanent foundation, and at least 6 feet from the house. In the R-2-10, R-2-8, RM and PUD zones ADUs are allowed only within detached single-family developments, and they are not allowed in the MH zone. Legal accessory structures built before October 1, 2026 (garage, shed, workshop) can be converted if they meet the same standards.

One attached ADU is allowed with a single-family home in the residential zones, either inside the house (such as a basement) or in an addition. An addition must share a common wall with the home's living area at least 20% of the addition's perimeter and may not connect through a breezeway, garage, storage or mechanical space; an internal doorway between the units is not required. Only one primary entrance may face the street, and additions must match the home's architectural style, materials, color and windows.

A detached ADU must meet whichever of three limits is smallest: 2,000 square feet of total gross area, a footprint no larger than 75% of the house's footprint, and a footprint no larger than the accessory-structure maximum in §21-11-2(a)(2). That accessory-structure table caps the combined size of all accessory structures at the lesser of 25% of the rear yard or 750 square feet (lots up to 14,999 sq ft), 1,000 (15,000 to 19,999), 1,500 (20,000 to 39,999) or 2,000 (40,000 or more), so on an 11,000 to 14,999 square foot lot the practical cap is 750 square feet of footprint. Height is either up to 15 feet with 10-foot side and rear setbacks, or up to 1.5 stories and 18 feet (never taller than the house) where the house's own setbacks are met. Section 21-11-1 sets no floor-area cap for attached ADUs.

Only the property owner may apply, and the owner must live in either the primary dwelling or the ADU as their primary residence (before Ordinance 26-55 it had to be the primary dwelling). The fee title owner must be an individual or the trustor of a family trust holding 50% or more; an LLC, corporation or partnership cannot qualify. Proof includes a government ID showing the address, a notarized affidavit, and supporting records such as a redacted W-2 or 1099, voter or vehicle registration, and utility bills.

A detached ADU needs 1 additional off-street space if it is under 650 total square feet and 2 spaces at 650 square feet or more, shown on a parking plan with the application; the council struck a proposed reduction for sites near transit. For attached ADUs the code requires off-street parking for the occupants under the citywide residential standards in Chapter 21-24 but names no extra space count, and the house itself must keep its required two-car garage plus two driveway spaces. Parking removed to create an ADU, including a converted garage, must be replaced on site, all occupant vehicles must fit on site, and street parking is reserved for visitors.

An attached or detached ADU needs an administrative Special Use Permit from the Community Development Department plus a business license, approved by staff against the fixed standards of §21-11-1 with no public hearing; a building permit is also required. Sandy's use table marks ADUs "S" (Special Use) rather than "C" (Conditional), and the code defines a special use permit as an approval for uses less intense than a conditional use, which is why this entry now codes it as permitted rather than conditional use. The permit is not transferable and ends on sale of the property, a change of the owner's residence, or expiry of the business license.

A detached ADU may not be rented for less than 30 consecutive days under any circumstances. An attached ADU may be rented short term only with a separate short-term rental special use permit and license under §21-11-26, and a property may not run a short-term rental and a 30-day-plus rental at the same time. The ADU must be occupied by one additional family, subleasing is prohibited, and renting requires the associated business license.