Garage conversion ADUs
How much does a garage conversion ADU cost in 2026?
Converting a garage is the cheapest legal path to an ADU on most California lots — typically 30–40% less than a same-size detached ADU because the slab, walls, and roof already exist. The 2026 range: $60,000–$200,000 depending on garage size, finish level, and state. Angi's most recent national data puts the average at $110,000 with a typical range of $60,000–$150,000.
Typical 2026 all-in cost
$60,000 – $200,000
150–400 $/sq ft
Angi Mar 2026; DQB Jan 2026; Kellow Feb 2026.
Three sources converge: Angi reports $60,000–$150,000 nationally with an average of $110,000 (Mar 2026). Dynamic Quality Builders' SoCal-specific data (Jan 2026): $100,000–$175,000 for basic-to-mid; $160,000–$200,000+ for premium. Kellow Construction (Feb 2026): $80,000–$175,000 California-wide.
By type and tier
| Type or tier | Range | Notes |
|---|---|---|
| Basic studio (400 sf, attached garage) | $60K–$130K | |
| Mid-finish 1BR (500–600 sf) | $140K–$175K SoCal | |
| Premium conversion | $160K–$200K+ | |
| State variation (Angi 2026) | CA $160K, NY $136K, FL $113K, TX $102K (averages) |
What moves the price most
Foundation condition
If the existing slab is in good shape, you save $5,000–$15,000 vs new construction. If it's cracked, sloped, or undersized, foundation reinforcement adds $5,000–$15,000 (DQB 2026).
Raising the roof for ceiling height
Most garages have 8-foot ceilings; some cities require taller for ADU habitability. Raising the roof adds $15,000–$30,000 (DQB 2026).
Utility runs from the main house
If the main house is more than ~30 feet from the garage, expect $5,000–$15,000 in trenching, paving repair, and panel work (DQB 2026).
Attached vs detached garage
Converting an attached garage is 20–30% cheaper than a detached one because plumbing, electrical, and HVAC connections are right there (Angi Mar 2026).
Cost breakdown
Share of total mid-point cost by line item (industry rules-of-thumb; actual ratios shift with site complexity and finish level).
| Line item | Share | Amount |
|---|---|---|
| Plans & permits | 10–12% | |
| Foundation reinforcement | 5–10% | |
| Framing/structure adjustments | 8–12% | |
| Roofing (if needed) | 0–5% | |
| Plumbing | 12–15% | |
| Electrical & panel | 10–12% | |
| HVAC (mini-split) | 4–6% | |
| Insulation & drywall | 8–10% | |
| Kitchen | 12–18% | |
| Bathroom | 8–12% | |
| Flooring | 4–6% | |
| Windows & doors | 4–6% | |
| Finishes | 5–8% |
Want sharper numbers for your specific project?
Run the calculator with your inputs, or get matched with 2–3 local builders who can quote your lot directly.
Garage conversion ADUs FAQ
- What's the cheapest way to convert a garage to an ADU?
- Convert an attached garage with existing utilities nearby, keep the existing slab and roof, choose builder-grade finishes, and stay under 750 sq ft to capture the impact-fee waiver. That combination lands in the $60,000–$110,000 range nationally (Angi Mar 2026 average).
- Do I need to replace the garage door?
- Yes. Most ADUs need a proper entry door and front-facing windows where the garage door used to be. Budget $4,000–$8,000 for windows and an exterior door package (DQB 2026).
- Will I lose parking? Does that hurt resale?
- California state law eliminates parking requirements for ADUs within half a mile of public transit, in historic districts, or in existing structures (garage conversions) — so most California garage conversions don't need to replace parking. Resale impact varies by neighborhood; in walkable urban areas the lost garage is often a wash with the added rental value.
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