Garage Conversion Cost · 2026 Pricing
Updated: June 2026
A Boise garage conversion runs $60k–$140k turnkey in 2026 — roughly 30–50% less than building new for the same square footage. Below: the cost by garage size, what actually drives the range, and the three line items that surprise homeowners.
Converting a garage into a permitted ADU in Boise costs $60k–$140k turnkey in 2026. A 1-car garage turned into a studio lands near the bottom of that range (~$55k–$85k); a standard 2-car garage built out as a full 1-bedroom runs $80k–$140k. The number depends almost entirely on the garage's existing condition — slab, sewer access, and whether it has any usable heat. Conversions run 30–50% cheaper than a new-build ADU of the same size because the foundation, walls, and roof already exist. The savings stop at the shell: insulation, electrical, plumbing, finishes, permits, and impact fees cost the same as new construction. Those figures are fixed-price and include everything through final inspection — they don't include furniture, landscaping, or premium appliance upgrades.
The biggest cost driver is square footage and what layout it supports. A 1-car garage only fits a studio; a 2-car can take a real 1-bedroom. These ranges reflect 2026 Boise conversion pricing.
| Conversion scenario | Typical size | Turnkey cost | Notes |
|---|---|---|---|
| 1-car garage → studio | ~300–360 sqft | $55k–$85k | Smallest, cheapest conversion. Studio layout with full kitchen and bath. |
| 2-car garage → studio | ~440 sqft | $60k–$95k | Extra width buys a defined sleeping zone and a real living area. |
| 2-car garage → 1-bedroom | ~440 sqft | $80k–$140k | Walled-off bedroom + living room. The most common Boise conversion. |
| Oversized / RV garage → 1BR+ | ~600 sqft | $90k–$150k | Room for a 1-bedroom plus den or office. Approaches small new-build cost. |
Comparing to a ground-up build? See the full Boise ADU cost guide or the detached ADU cost breakdown.
Two identical-looking garages can quote $30k apart. These four factors are why — and all four are things we inspect before quoting, not after.
Most garage slabs were poured for cars, not living space — no thickened edges, shallow footings, and no frost protection at the door opening. Bringing the slab to habitable code (perimeter footings, the old overhead-door opening infilled and footed, sometimes a moisture barrier and self-leveling pour) is the single most variable line item, $6k–$20k depending on what we find.
A garage typically has one circuit and a hose bib. A dwelling needs a full electrical subpanel, plumbing run to the slab for kitchen and bath, and a code-compliant heating system. A ductless mini-split heat pump (one or two heads) runs about $7k–$11k installed and is the usual pick — most garages have no compliant heat at all.
Garage walls, ceilings, and floors are almost never insulated to dwelling standard, so plan on a full insulation + air-sealing package. Each bedroom needs an egress window meeting Idaho code (5.7 sqft net clear opening). Cutting a new opening in an existing garage wall is routine but adds cost — roughly $1.5k–$3k per window.
A conversion to a dwelling pulls the same City of Boise ADU permit path as new construction — building, electrical, plumbing, mechanical, plus impact and connection fees that usually total $8k–$15k. If the garage has no sanitary connection, a new sewer lateral is the other big surprise line, $3k–$8k depending on the run to the main.
A garage conversion contract should cover all six of these. If a cheaper bid doesn't, that's usually where the change orders come from.
Remove the overhead door, frame the infill wall, demo any non-conforming finishes, and prep the slab.
Perimeter footings, door-opening infill footing, and slab leveling/moisture control as needed for habitable use.
Electrical subpanel + circuits, plumbing rough-in to slab, and a code-compliant mini-split heating system.
Walls, ceiling, and floor insulated to 2018 IECC + Boise amendments, plus egress windows for any bedroom.
Drywall, paint, cabinets, counters, flooring, fixtures, and an appliance package per your finish level.
All city permits, impact and connection fees, inspections, and the final certificate of occupancy.
A conversion is cheaper up front — $60k–$120k versus about $170k for a 491 sqft Kingfisher new build. But a detached ADU usually adds more appraised value ($50k–$80k for a detached unit) and rents $200–$400/month higher than a converted attached space of the same size, because tenants pay a privacy premium for a stand-alone home.
The conversion wins when you have a sound detached garage you don't need for parking and you want the lowest entry cost. New detached wins when you want maximum rent and resale, when your garage is in rough shape, or when you'd rather keep the garage and add a Sandpiper or Osprey that gives you both. We build all of it, so the recommendation isn't tied to one answer — compare them side by side in the detached vs. garage conversion guide.
A Boise garage conversion runs $60k–$140k turnkey in 2026, depending on the garage's size and condition. A 1-car studio conversion lands around $55k–$85k; a standard 2-car converted to a 1-bedroom runs $80k–$140k. That's fixed-price and includes foundation upgrades, MEP, insulation, finishes, permits, and connection fees — not furniture or landscaping.
Yes — typically 30–50% less than a comparable new-build ADU. A 2-car garage conversion runs $60k–$120k versus about $170k for a 491 sqft Kingfisher new build. The savings come from reusing the foundation, exterior walls, and roof. Where you don't save: insulation, MEP, finishes, and permits are the same either way.
Three line items surprise people: the foundation (garage slabs rarely have footings rated for living space, $6k–$20k to bring to code), a new sewer lateral if the garage has no sanitary connection ($3k–$8k), and heating (most garages need a $7k–$11k mini-split). We pre-walk all three during the free lot check so the number you get is the number you pay.
Usually a foundation upgrade, not a full replacement. The existing slab often stays, but we add perimeter footings, foot the infilled door opening, and address moisture or unevenness. How much depends on the slab's age and condition — it's the most variable part of the estimate, which is why we inspect it before quoting.
Often yes, but attached conversions add a fire-separation requirement between the ADU and the main house, and you lose covered parking and interior access. Many Boise homeowners prefer converting a detached garage, or building a Sandpiper or Osprey that gives back a garage plus a dwelling. We'll tell you which path is cheaper for your specific lot.
Free Lot Check · 24-Hour Response
We inspect the slab, sewer, and setbacks first, then quote a fixed price. Or call (208) 297-2036.
