What the interior finish actually costs per square foot
The $40-$90 per square foot range covers the finish work itself: framing within the existing footprint, insulation, drywall, mud and texture, paint, trim, interior doors, and flooring. A 750 sq ft basement apartment at a mid-grade $60/sq ft is about $45,000 of finish before the bath and kitchen. The low end ($40-$55) means standard carpet/LVP, builder-grade trim, and a simple layout; the high end ($75-$90) reflects tile, solid-core doors, upgraded lighting, soundproofing between units, and a more divided floor plan with separate living, sleeping, and kitchen zones. Because an ADU is a full living space, not just a rec room, you're finishing more rooms and more walls per square foot than a typical basement, which pushes most ADUs toward the middle-to-upper part of that band.
Kitchenette and bathroom adders for a livable unit
A code-legal basement apartment needs its own bathroom and a kitchen, and those two rooms drive a big share of the budget. An added basement bathroom runs about $8,000-$18,000 depending on whether drain lines and a vent stack already reach that corner; cutting and patching slab for new plumbing sits at the top of that range. A functional kitchenette, a sink, counter, cabinets, an apartment-size range or cooktop, and a fridge space, typically adds $5,000-$15,000, and a full second kitchen with a 220V range circuit and range hood ducting costs more. Every new water line, drain, and fixture requires a plumbing permit, and a true second kitchen means added electrical capacity, so price these as their own line items rather than folding them into the per-square-foot figure.
What drives the price up or down
Three things move a basement ADU budget the most. First, existing infrastructure: if the basement already has rough-in plumbing, an egress window, and adequate panel capacity, you're mostly finishing; if not, those become real costs. Second, egress and the unit's independent entrance, Utah requires every sleeping room to have an emergency escape opening (net clear 5.7 sq ft, sill no higher than 44 inches, with a window well at least 9 sq ft and 36 inches deep), and an internal ADU needs an egress path that doesn't route through the main home's living space. Third, separation and systems: soundproofing, fire separation between units, a second water heater or HVAC zoning, and a dedicated sub-panel all add cost. Radon matters too, one in three Utah homes tests above the EPA action level of 4 pCi/L (the state average is about 5.3), so a mitigation system is a smart, often-required add for a rented living space.
The $50,000 R101 line and how bigger ADUs get handled
Wasatch Finish holds a Utah DOPL R101 license, which covers non-structural finishing work on projects under $50,000. A modest basement apartment, finishing within the existing footprint with a bath and kitchenette tied into existing rough-ins, often fits inside that envelope. When an ADU is larger, higher-finish, or needs structural and mechanical work, the project is either phased into separate sub-$50k scopes or the specialty pieces are coordinated with and referred to the appropriate licensed trades. Cutting a brand-new egress window well into the foundation, adding a separate exterior entrance through the foundation wall, moving or adding a sub-panel, or relocating a plumbing stack are structural/MEP tasks done by those licensed contractors. We do the interior finish, framing within the footprint, insulation, drywall, paint, trim, doors, flooring, and the bath and kitchenette finish, so the unit is move-in ready.
Permits, impact fees, and Utah's internal-ADU law
Since HB 82 passed in 2021, Utah cities must allow an internal ADU by right in most single-family zones, meaning a basement apartment within your home's existing footprint generally can't be forced through a conditional-use hearing if it meets the standards. Cities can still require a building permit, a rental license or registration, one extra off-street parking space, and compliance with building, egress, and fire-separation codes, and many keep an owner-occupancy condition. The real money-saver: under Utah Code 11-36a-202, internal ADUs created inside an existing primary dwelling are exempt from impact fees, which typically saves $5,000-$15,000 versus a detached unit. Utah Code also requires a licensed general contractor to pull the permit for a second dwelling unit, and plan review for an ADU with a kitchen and bath usually takes about two to four weeks. Always confirm specifics with your city, rules vary by jurisdiction across Highland, Alpine, American Fork, Lehi, Draper, Sandy, and South Jordan.
Bottom line
Budget about $40-$90/sq ft for the interior finish, plus $8k-$18k for a bath and $5k-$15k for a kitchenette; internal ADUs skip impact fees, and Wasatch Finish does the finish under $50k while licensed trades handle any structural or MEP work.
Questions
How much does it cost to finish a basement ADU in Utah?
A basement ADU in Utah usually costs about $40-$90 per square foot for the interior finish, plus roughly $8,000-$18,000 for the added bathroom and $5,000-$15,000 for a kitchenette. A typical 700-1,000 sq ft basement apartment lands around $45,000-$110,000 depending on finish level, existing rough-ins, and how much plumbing and electrical work is needed. A walkout basement with plumbing already roughed in finishes for far less than a bare slab.
Are basement ADUs legal in Utah?
Yes, internal basement ADUs are legal across Utah under HB 82, passed in 2021, which requires cities to allow an internal accessory dwelling unit by right in most single-family residential zones. The unit must be inside the home's existing footprint and intended for long-term rental of 30 days or more. Cities can still require a building permit, a rental license, one extra parking space, and code compliance, and some keep an owner-occupancy rule, so confirm details with your specific city.
Do you pay impact fees on a basement ADU in Utah?
No, internal basement ADUs are exempt from city impact fees in Utah under Utah Code 11-36a-202, because the unit is created within an existing primary dwelling rather than as new construction. That exemption typically saves $5,000-$15,000 compared with a detached ADU, which many cities do charge impact fees on. You'll still pay normal building, plumbing, and electrical permit fees, but the impact-fee waiver is a meaningful reason basement conversions pencil out better than backyard units.
What does Wasatch Finish handle on a basement ADU versus other trades?
Wasatch Finish handles the interior finish of a basement ADU under our Utah DOPL R101 license: framing within the existing footprint, insulation, drywall, paint, trim, interior doors, flooring, and the bath and kitchenette finish, on projects under $50,000. Structural and mechanical work, cutting a new egress window well into the foundation, adding a separate exterior entrance, moving a sub-panel, or relocating a plumbing stack, is done by the appropriate licensed trades, which we coordinate with or refer out so the whole project stays code-compliant.
Does a basement ADU need an egress window in Utah?
Yes, every sleeping room in a Utah basement ADU needs an emergency escape and rescue opening, and the unit needs an egress path that doesn't pass through the main home. The window must give a net clear opening of at least 5.7 square feet, minimum 24 inches high and 20 inches wide, with the sill no more than 44 inches above the floor. A below-grade window also needs a window well at least 9 square feet with a 36-inch projection. Cutting a new well into the foundation is structural work handled by a licensed trade.