ADU Cost in Filer, Idaho
What it really costs to build an ADU in Filer — by type, with Filer-specific permit fees, rent, and ROI. Straight from local ADU builders.
Quick Answer
An ADU in Filer, Idaho typically costs $80,000 – $150,000 for a garage conversion, $150,000 – $350,000 for a detached new build, and $150,000 – $280,000 all-in for a pre-fab/modular unit (roughly $150 – $300 per square foot finished). Add permits and impact fees on top.
ADU Cost by Type in Filer
| ADU Type | Typical Filer Cost | Timeline | Best For |
|---|---|---|---|
| Garage Conversion | $80,000 – $150,000 | 2–4 months | Lowest cost; existing garage in good shape |
| Detached New Build | $150,000 – $350,000 | 4–8 months | Maximum size + design flexibility |
| Pre-Fab / Modular | $150,000 – $280,000 | 8–14 weeks on-site | Faster on-site; straightforward lots |
| Per square foot (finished) | $150 – $300 / sq ft | ||
Permits & Fees in Filer
Confirm permit fees with the City of Filer (208-326-5000). Utility connection/capacity fees may apply.
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 Filer
A 1-bedroom ADU in Filer typically rents for $750–$1,100/month long-term (estimate). At this rate, an ADU often offsets much or all of its financing payment within a few years, on top of the 20–30% property value increase ADUs typically deliver (per FHFA research).
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 Filer.
More for Filer Homeowners
ADU Rules in Filer
Zoning authority, size limits, setbacks, and SB 1354 status for Twin Falls 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 Filer
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.