Garage Conversion Cost Guide: ADU and Living Space Remodeling (2026)
A full 400-to-500 sq ft 2-car garage conversion ranges from $35,000 for a simple home office or gym to $85,000+ for a fully plumbed, permitted ADU rental.
Converting a garage into conditioned living space is one of the most cost-effective ways to add rental income or multi-generational housing because the exterior foundation, wall framing, and roof are already erected.
| Scope of Work | Low Range | High Range |
|---|---|---|
| Garage door removal & exterior wall framing | $3,500 | $6,500 |
| Slab vapor barrier & rigid foam insulation | $2,200 | $4,000 |
| Wall and ceiling insulation (R-19/R-38) | $2,000 | $3,800 |
| Electrical subpanel (100A) & wiring | $4,000 | $7,500 |
| Plumbing rough-in (trenching concrete for bath/kitchen) | $6,500 | $12,000 |
| Mini-split heating and cooling | $3,500 | $5,500 |
| Drywall, painting, and interior doors | $5,000 | $8,500 |
| Flooring (Waterproof LVP) | $2,200 | $4,000 |
| Bathroom fixtures and compact kitchen build | $10,000 | $18,000 |
| Permits, impact fees & architectural plans | $2,500 | $6,000 |
| **Total Turnkey ADU Project** | **$41,400** | **$75,800** |
Slab Moisture Isolation and Insulation
Garage slabs lack subterranean vapor barriers. Installing living space flooring directly over concrete invites moisture migration. Contractors must apply an epoxy moisture barrier or install rigid insulation and sleepers before subflooring.
Plumbing Trenching and Utility Runs
Cutting through 4-inch reinforced concrete to install 3-inch waste drain lines for toilets and showers represents a major labor driver ($5,000 to $10,000 alone), particularly if the main sewer tie-in is located on the far side of the foundation.
Frequently asked questions
- Do you need a separate electrical subpanel for an ADU garage conversion?
- Yes. Most jurisdictions require a 100-amp subpanel to support dedicated electric cooktops, water heaters, and mini-split heat pumps.
- What happens to off-street parking requirements?
- Many states (such as California under AB 68/AB 881) have eliminated replacement off-street parking mandates if the property is within a half-mile of public transit.
Sources and references
More in Cost guides
- Kitchen Remodel Cost Breakdown: Line-by-Line Pricing Guide (2026)
- Bathroom Remodel Cost Guide: Half Bath, Full Bath & Master Suite (2026)
- Deck Construction Cost Guide: Pressure-Treated Wood vs Composite (2026)
- Hardwood Flooring Installation Cost Guide: Solid, Engineered & LVP (2026)
- Attic Conversion Cost: Bedroom and Master Suite Living Space (2026)
- Roof Replacement Cost Guide: Architectural Shingles vs. Standing Seam Metal