We Handle Every Permit So You Don't Have To
ADU permitting in Twin Falls involves a Zoning Use Permit application, multiple trade permits, and weeks of follow-up across city departments. We manage the entire process from first submission to Certificate of Occupancy.
Quick Answer
An ADU in Twin Falls requires a $250 Zoning Use Permit (filed with Twin Falls Planning & Zoning at 203 Main Ave E), plus a building permit, separate electrical/plumbing/HVAC trade permits, and a final Certificate of Occupancy after inspections. Total permitting timeline is 4–8 weeks from complete submission. We handle every application, follow-up, and inspection on your behalf — you never speak to a city office.
Why ADU Permitting Is Complicated
An ADU in Twin Falls isn't just one permit — it's a Zoning Use Permit application ($250 for ADUs), a building permit, electrical permit, plumbing permit, mechanical (HVAC) permit, utility connection permits, and impact fee payments. Each has its own application, its own review process, and its own inspection schedule.
Idaho follows the 2018 International Residential Code (IRC), and Twin Falls enforces additional ADU-specific requirements under Title 10-6-10. Getting it wrong means delays, re-submissions, and potentially costly plan changes. Incomplete applications are not accepted or scheduled for review by the city.
ADU Requirements — Twin Falls Title 10-6-10-B
Per Title 10-6-10-B, your ADU must not exceed 45% of your principal residence's living space, must match the existing roof pitch, siding, and windows, and must share water/sewer/sanitation with the primary dwelling (no separate utility meters are permitted). One additional off-street parking space is required. Setbacks for the ADU follow the same requirements as the principal building.
What We Handle:
- ✓Zoning Use Permit application — completed, signed, and submitted with the $250 ADU fee to Twin Falls P&Z
- ✓Proof of property control — deed, title report, or purchase agreement as required by the application
- ✓Title 10-6 compliance documentation — verifying your project meets all zoning standards
- ✓Written project description — detailed narrative of scope, use, and construction approach
- ✓Scaled site plan — 8.5"x11" with measurement scale, property lines, north arrow, street names, and color elevations for new buildings
- ✓Trade permits — electrical, plumbing, mechanical (HVAC)
- ✓Impact fees — approximately $6,000-$10,000 depending on size and jurisdiction
- ✓All inspections — foundation through final CO
Twin Falls 7-Step Zoning Use Permit Process
The City of Twin Falls follows a formal 7-step application and decision process for Zoning Use Permits. We manage every step on your behalf.
Detached Accessory Building Setbacks (Title 10-6-10-A)
Setback requirements for detached accessory buildings depend on building height and zoning district. Buildings 15 feet or under follow simplified setbacks; buildings over 15 feet must comply with district-specific requirements.
| Height / District | Front | Side | Rear | Max Height |
|---|---|---|---|---|
| 15 ft or under (all districts) | 20' | 3' | 3' | 15' |
| Over 15 ft — TN-1 | 20' | 7' | 20' | 35' |
| Over 15 ft — TN-2 / TN-3 | 20' | 5' | 15' | 35' |
| Over 15 ft — All other districts | 20' | 5' | 15' | 35' |
Source: Twin Falls Municipal Code, Title 10-6-10-A — Detached Accessory Building Setbacks
Inspection Stages We Coordinate
Twin Falls Planning & Zoning
203 Main Ave E, Twin Falls, ID 83303
Phone: (208) 735-7267
Email: tfplanning@tfid.org
Zoning Use Permit applications and zoning questions
Twin Falls Building Safety
Phone: (208) 735-7238
Building code and inspection questions
Idaho Law Is on Your Side
Idaho House Bill 166 prevents jurisdictions from imposing outright bans on ADUs. And as of July 1, 2023, HOAs cannot create or enforce rules that generally ban ADUs on detached, owner-occupied properties. Learn more about your rights →
Our Permitting Process
A streamlined approach that minimizes delays and gets you building faster
Document Preparation
We compile proof of property control, Title 10-6 compliance documentation, a written project description, and a scaled site plan with color elevations — every item required by Twin Falls Planning & Zoning.
Application Submission
Complete Zoning Use Permit application ($250 fee) filed with Twin Falls P&Z, along with building permit, trade permits, and utility connection applications. Incomplete applications are not accepted or scheduled for review.
Plan Review + Decision
We respond to reviewer comments and coordinate through the city's 7-step review process. Our code-compliant plans minimize review cycles. Decisions include a 15-day appeal window per city procedure.
Permit Issuance + Inspections
Once approved, we manage all inspections throughout construction: foundation, framing, rough-in, insulation, and final inspection for Certificate of Occupancy.
Permit Notes by Jurisdiction
Every Magic Valley and Wood River Valley jurisdiction has its own quirks. Twin Falls is the most documented (and the strictest about design consistency), while Blaine County jurisdictions in the Wood River Valley layer design review on top of standard permitting. Here is what we have learned working with each.
City of Twin Falls — Planning & Zoning
203 Main Ave E · 208-735-7267 · tfplanning@tfid.org
- • Governing code: Title 10, Section 10-6-10-B of the Uniform Development Code
- • Critical rule: 45% size limit on ADU vs. principal residence living space — verified at the Feasibility Check
- • Design review: ADU roof pitch, siding, and windows must match the principal dwelling. Reviewer rejection is most common on this point.
- • Timeline: 4-8 weeks typical, plus 15-day appeal window after staff decision
- • Incomplete applications are not scheduled for review — we triple-check before submission
Jerome, Burley, Rupert, Buhl, Filer, Kimberly
Each has its own city planning department
- • Governing framework: Idaho state building code + local zoning ordinances
- • HB 166 protection: No outright ADU bans permitted; each jurisdiction has a defined process
- • Permit fees and process vary by city — generally simpler than Twin Falls but with less documentation
- • Setbacks and lot coverage rules vary by zone — we confirm yours at the Feasibility Check
- • Timeline: Often faster than Twin Falls (3-6 weeks typical)
Gooding County (Wendell, Gooding, Hagerman)
- • In-city limits: each city's own planning office handles ADU permits
- • Rural / unincorporated parcels: Gooding County Planning & Zoning handles permitting
- • Two-step verification: we confirm your exact jurisdiction (city vs. county) before permit submission — the rules differ
- • Larger lot sizes typical — setback compliance is usually easier than higher-density Twin Falls neighborhoods
Wood River Valley — Blaine County jurisdictions (Bellevue, Hailey, Ketchum)
- • Bellevue: Contracts SAFEbuilt for inspections; coordinates with Blaine County for land-use matters. Schedule inspections at (208) 913-0188.
- • Hailey: Community Development at 115 S Main St (208-788-9815). Active ADU market, well-staffed. Old Hailey historic district adds design review.
- • Ketchum: Planning & Building at 191 5th St West (208-726-7801). Comprehensive design review is standard — not an exception. Plan for an extra 2-4 weeks vs. Magic Valley jurisdictions.
- • Wood River Valley ADUs often serve workforce housing for resort-area employees; jurisdictions are friendlier to these projects than to second-home accessory units
- • Distance factor: 75-95 miles from Twin Falls; project management cost reflects the travel time
Common Reasons Twin Falls ADU Permits Get Held Up
- Roof pitch / siding mismatch with the primary dwelling — the #1 reason for review comments under Title 10-6-10-B
- Site plan missing required elements (scale, property lines, north arrow, color elevations on 8.5"x11" paper)
- Setback or lot-coverage calculations incorrect for the zoning district
- Attempting to propose separate utility meters (prohibited by code)
- ADU size exceeds 45% of the principal residence's living space
- Existing accessory structure conversion that doesn't meet current code (insulation, egress, ceiling height)
- Incomplete proof of property control
Our submissions are pre-vetted against all of these before we file. The Feasibility Check exists specifically to surface any of these issues before you commit to design and construction costs.
Let Us Handle the Paperwork
Permitting is one of the most confusing parts of an ADU project. Start with a free Readiness Call and we'll guide you through every step.