ADU Cost in Ketchum, Idaho
What it really costs to build an ADU in Ketchum — by type, with Ketchum-specific permit fees, rent, and ROI. Straight from local ADU builders.
Quick Answer
An ADU in Ketchum, Idaho typically costs $110,000 – $190,000 for a garage conversion, $200,000 – $450,000+ for a detached new build, and $190,000 – $340,000 all-in for a pre-fab/modular unit (roughly $220 – $400 per square foot finished), reflecting the Wood River Valley's higher labor and logistics costs. Add permits and impact fees on top.
ADU Cost by Type in Ketchum
| ADU Type | Typical Ketchum Cost | Timeline | Best For |
|---|---|---|---|
| Garage Conversion | $110,000 – $190,000 | 2–4 months | Lowest cost; existing garage in good shape |
| Detached New Build | $200,000 – $450,000+ | 4–8 months | Maximum size + design flexibility |
| Pre-Fab / Modular | $190,000 – $340,000 | 8–14 weeks on-site | Faster on-site; straightforward lots |
| Per square foot (finished) | $220 – $400 / sq ft | ||
Permits & Fees in Ketchum
Confirm permit + comprehensive design-review fees with Ketchum Planning & Building (208-726-7801).
These are in addition to the construction cost above. We get exact fee quotes from the local office for your specific project during the Feasibility Check — see our full line-item cost breakdown + ROI calculator for how the numbers add up.
Rental Income & ROI in Ketchum
A 1-bedroom ADU in Ketchum typically rents for $1,300–$2,200/month long-term (estimate). Wood River Valley rents are among the highest in Idaho — the higher build cost is offset by premium rent that shortens the payback period considerably.
Want the exact numbers for your property and goals? Our free eligibility check tells you your maximum ADU size, and the Feasibility Check gives you a good/better/best budget for Ketchum.
More for Ketchum Homeowners
ADU Rules in Ketchum
Zoning authority, size limits, setbacks, and SB 1354 status for Blaine County.
Full Cost Breakdown
13-category line-item breakdown + interactive ROI calculator.
Am I Eligible?
Instant check: your max ADU size + which floor plans fit your lot.
Financing
HELOC, construction loan, cash-out refi — and Idaho lender options.
Get Your Real ADU Budget for Ketchum
Start with a free 10-15 minute Readiness Call, then book a Feasibility Check for a detailed good/better/best budget tailored to your property.