Turn Your Garage Into a Fully Permitted ADU
Garage conversions are the fastest, most affordable way to add an ADU in Twin Falls. You already have the structure — we help you plan the conversion, and a licensed contractor we work with turns it into a legal, livable unit.
Why a Garage Conversion?
Most homeowners who want an ADU already have a head start — their garage. Converting an existing garage to an ADU costs significantly less than a ground-up new build because the foundation, framing, and roof are already there. What you're really doing is finishing and converting an existing space.
A garage conversion is also typically faster — 2-4 months of construction versus 4-8 months for a new detached build. And because the structure already exists, there are fewer unknowns.
What Does a Garage Conversion Cost? Two Honest Answers
National cost guides: about $29,000–$67,000 for an ADU-grade garage conversion (This Old House 2026 price guide, $31,500–$73,200, adjusted ~8% lower for Twin Falls construction costs)
Twin Falls ADU projects: $80,000–$150,000
Why the gap? A legal, rentable ADU conversion typically adds fire separation, egress windows, insulation to code, separate or upgraded utilities, permits and impact fees, and design. The national guide figures often describe simpler conversions.
What a Garage Conversion Includes:
- ✓Foundation/slab evaluation and upgrades
- ✓Exterior wall insulation (R-21 for Climate Zone 5/6)
- ✓Garage door removal and framing of new wall and entry
- ✓Egress windows in bedroom (code required)
- ✓Full bathroom — plumbing rough-in and finish
- ✓Kitchenette or full kitchen rough-in and finish
- ✓Electrical panel upgrade and interior wiring
- ✓HVAC — mini-split or tied to existing system
- ✓Drywall, flooring, paint, and trim
- ✓Exterior finish to match principal dwelling
Twin Falls Code Requirements for Garage Conversions
In Twin Falls, converting a garage to an ADU means converting an existing structure — and per Title 10, Section 10-6-10-B, the converted structure must meet all ADU requirements of the Uniform Development Code.
Design Match Required
The converted garage must be consistent with the existing roof pitch, siding, and windows of the principal dwelling. The garage door must be replaced with siding and a window or new entryway that matches your home.
45% Size Rule
Your ADU (including the converted garage) cannot exceed 45% of your principal residence's living space per Title 10-6-10-B. A 1,500 sq ft home = max 675 sq ft ADU.
Shared Utilities Required
Per Title 10-6-10-B(vii), your converted garage ADU must share water, sewer, and sanitation with the primary dwelling. No separate meters allowed.
Zoning Use Permit
A $250 Zoning Use Permit is required from the Twin Falls Planning and Zoning Department (203 Main Ave E, 208-735-7267) plus all standard building permits.
Is Your Garage a Good Candidate?
Not every garage is an ideal conversion candidate. Key factors include: concrete slab condition, ceiling height (8 ft minimum recommended), proximity to existing plumbing, and current roof structure. Our Feasibility Check evaluates all of these — you'll know exactly what you're getting into before you commit.
Learn about the Feasibility Check →Garage Conversion vs. New Detached Build
Not sure which is right for you? We compare both options during your Feasibility Check — cost, timeline, ROI, and practical considerations for your specific property. See our detailed comparison:
Garage Conversion vs. New Build →How the Garage Conversion Process Works
A clear 4-step path from assessment to move-in
Structural Assessment
We evaluate your garage's foundation, slab, framing, roof, and walls to determine what can be reused and what needs upgrading — before you spend a dollar on design.
Custom Conversion Design
The floor plan is planned to maximize the space, add the required egress windows and entry, route plumbing through the existing structure, and match your home's exterior per Twin Falls code. The licensed contractor we work with produces the drawings.
Permitting
The contractor handles the Twin Falls Zoning Use Permit ($250) and all building permits for structural, electrical, plumbing, and mechanical work. Your garage conversion is fully permitted and inspected at every stage.
Construction + Finish
The contractor handles everything — insulation, framing, plumbing, electrical, HVAC, drywall, flooring, and finishes — and hands you the keys and the Certificate of Occupancy.
Common Questions
How much does a garage conversion ADU cost in Twin Falls?
A garage conversion is typically the lowest-cost ADU in Twin Falls, around $80,000 to $150,000 and about 2-4 months of construction, because the foundation, framing and shell already exist. You pay mainly for interior buildout, plumbing, electrical, HVAC, insulation and finishes. The trade-off is losing the garage space. Permits and fees are in addition to these figures.
Find Out If Your Garage Is a Good Candidate
Book your $499 assessment — applied to your construction contract by the contractor. We look at your garage in person and give you a written report within 5 business days: what it can become and what it would cost. Want to talk first? Start with a free Readiness Call.