Utah’s new ADU law opens more backyard cottage possibilities

A Utah law that took effect Oct. 1 requires covered municipalities to allow detached accessory dwelling units on qualifying residential lots, expanding options for Salt Lake County homeowners. Ironwood Custom Builders says the rule still leaves major site, zoning, utility and HOA hurdles before a project can move forward.

Why it matters: - Utah homeowners now have a clearer path to build a detached accessory dwelling unit, or ADU, on certain lots. - The new law could expand housing options for multigenerational families, rental income and aging-in-place plans. - The change matters most in Salt Lake County and other covered municipalities where backyard cottages were previously harder to permit.

What happened: - A Utah law took effect Oct. 1 and requires covered municipalities to permit detached ADUs on qualifying residential lots. - Ironwood Custom Builders is urging homeowners to confirm whether a property is actually feasible before spending money on plans. - The company is based in Cottonwood Heights and serves Salt Lake City and surrounding communities.

The details: - Under Senate Bill 284, a covered municipality must allow a detached ADU on a lot of at least 11,000 square feet that contains a single-family dwelling, if a single-family dwelling is a permitted use on that lot. - In a primarily residential zone, a municipality may not require a conditional-use permit for the detached unit. - The law does not prevent cities from allowing detached units on smaller lots. - Cities may still set rules for setbacks, building size, lot coverage, owner occupancy and utility service. - Applicable building, health and fire codes still apply. - Cities may limit parking requirements to no more than one space for an ADU smaller than 650 square feet, or two spaces for an ADU of 650 square feet or larger. - Ironwood says homeowners should check parcel size, zoning, available building area, setbacks, utility access, parking and HOA documents before investing in detailed plans. - A building permit and the applicable reviews are still required. - Homeowners should also review HOA restrictions; Utah’s Department of Commerce advises that an HOA may prohibit a detached ADU even where municipal rules allow one. - More information is available in Ironwood’s ADU services.

Between the lines: - The law broadens eligibility, but local control still matters a lot. - The biggest obstacles for many homeowners may be the physical site, utility capacity and private HOA rules, not just the state statute. - Some municipalities already allow detached ADUs under standards that are more flexible than the new state threshold, so the practical effect will vary by city.

What’s next: - Homeowners will need to check local zoning and permitting rules before moving from concept to design. - Municipal review, building permits and code compliance will remain part of the process. - Ironwood expects the first question to be whether a specific property can accommodate a detached unit before the homeowner commits to construction plans.

The bottom line: - Utah opened the door wider for detached ADUs on qualifying lots, but each backyard still has to pass the test of local rules, site constraints and HOA restrictions.