Build an accessory dwelling unit in Utah

An accessory dwelling unit is a secondary, self-contained home on the same lot as a primary single-family dwelling — with its own living, sleeping, cooking, and sanitation facilities. In Utah, ADU is the legal and planning term that covers:

• Internal ADUs — inside the existing house (basement, attic with proper egress, or reconfigured main floor)
• Attached ADUs — additions connected to the primary structure
• Detached ADUs — backyard cottages, often called casitas or granny flats in consumer language

Utah ADU Builder exists to evaluate whether your property can support an ADU, then connect with independent partners who can help navigate local design, permitting and construction.

Two pillars matter most for homeowners:

1. Internal ADUs — statewide framework (H.B. 82 era) establishing one internal ADU as a permitted use in many owner-occupied single-family residential situations, with local conditions on parking, owner occupancy, and possible bans on lots ≤6,000 sq ft.
2. Detached ADUs — S.B. 284 — specified municipalities must allow one detached ADU as a permitted use on qualifying lots of 11,000+ sq ft with a permitted single-family dwelling. Operative October 1, 2026. Local design standards remain.

County assessor labels are not zoning. Always confirm the zone with the city. Our how it works page explains how the public map approximates these rules.

Choose based on cost, privacy, timeline, and lot size — not whichever word you heard first on social media. Internal units usually win on cost and speed. Detached units win on separation and outdoor identity. Aging-in-place families often prefer internal/attached; rental investors with large lots often prefer detached.

Utah ADU Builder calibrates to mid-market Northern Utah construction — not coastal brochure pricing. Broad ranges homeowners hear from us:

• Internal / basement: often roughly $60k–$150k
• Garage conversion: often roughly $60k–$175k
• Detached: commonly mid-teens to low-$200ks for functional units; complexity adds

Run a fuller model in the interactive estimator.

For statewide detached protection under S.B. 284: 11,000+ sq ft in a specified municipality (operative Oct 1, 2026). For internal ADUs: no 11k requirement, but cities may prohibit internal ADUs on lots of 6,000 sq ft or less. Between 6k and 11k, internal is often the statewide story while detached depends on local ordinance.

We concentrate on the Wasatch Front — Salt Lake, Utah, Davis, and Weber counties — with additional work in St. George and Logan. Deep links many homeowners use first:

• Salt Lake City
• West Jordan
• Sandy
• Provo
• Orem
• Lehi
• Layton
• Bountiful
• Ogden

Full index: Utah city ADU guides.

Internal projects can sometimes complete on the order of several months when design and city review cooperate. Detached projects usually take longer. Pre-October 2026 detached entitlement varies by city. Use the sketch below as orientation — not a contract schedule.

Yes — through equity products, renovation/construction loans, or cash. Lenders differ on counting projected rent. We produce estimates and plans that finance conversations can actually use. We do not originate loans; we help you show up prepared.

Confirm zoning/ADU eligibility → prepare architectural (and often structural / energy) plans → submit building permit → respond to corrections → obtain permit → build with inspections → final/occupancy as required → complete any rental registration. Skipping the eligibility conversation is how people buy the wrong plans.

Use our before you build checklist alongside a city counter visit.

Often yes — especially under statewide internal ADU expectations and as allowed for cities under S.B. 284 for detached units. Documentation varies. If you will not live on-site, disclose that immediately so we check local ordinance instead of assuming statewide paths apply.

Not automatically. Statewide ADU frameworks aim at longer stays (30+ days for many internal ADUs; cities may require longer for detached). STR licensing, overlays, and HOA rules are separate. Build the ADU for compliant long-term use first unless your city explicitly green-lights short-term.

We are an evaluate–design–build team for Utah ADUs. Public tools on this site help you screen a parcel; professionals then take you through design, pricing, permitting coordination, and construction. Years on Utah jobsites mean we speak both “statute” and “inspector” — and we will tell you when a viral floor plan will not fit your setbacks.

Open Project Studio · Start a project · Book a free review

It is a powerful first pass using public parcel and municipal data — not a substitute for zoning confirmation. It cannot see every easement, HOA covenant, or utility constraint. Green/gold/amber colors are educational signals. Treat “likely” as “worth a professional and city conversation,” not “you are permitted.”

Evaluate your property on the map.

We maintain Utah-oriented packages for internal suites, garage conversions, and detached cottages across finish tiers. Packages are starting points — every lot edits the plan. See designs and the studio workflow.

Internal ADUs commonly trigger an extra parking space conversation. For detached ADUs in specified municipalities under S.B. 284, state law caps how much parking cities can demand — but you still need a workable site plan. Alleys, tandem pads, and garage conversions that delete stalls need careful counting.

(1) Map your address. (2) Open your city guide. (3) Decide whether family housing or rental income is the primary story. (4) Start a project intake or book a property review. (5) Call or text 385-355-1741 if you want to talk through the lot live. Educational pages get you oriented; professionals get you built.

Use the city ADU database for county-grouped guides. Pair any city page with this ADU overview and the granny flat or casita guides depending on the product you want to build.

No. Content is educational. Statutes change, cities amend ordinances, and every parcel has unique facts. Verify with your city planning and building departments — and consult qualified legal counsel when you need legal conclusions. Utah ADU Builder provides professional design-build services and informed guidance, not legal representation.