1,000 sq ft ADUs
How much does a 1,000 sq ft ADU cost in 2026?
1,000 sq ft is the upper end of California's standard ADU size cap for two-or-more-bedroom units. The 2026 range: $150,000–$400,000 nationally; $250,000–$400,000 in Southern California; $350,000–$550,000 in the Bay Area for a typical 600–1,000 sf unit (Barcci Builders 2026).
Typical 2026 all-in cost
$150,000 – $400,000
150–400 $/sq ft · 1,000 sq ft, mid-finish, slab foundation.
Kellow Feb 2026; DQB Jan 2026; Barcci Mar 2026.
Kellow Construction's range for 1,000 sf California ADUs (Feb 2026): $150,000–$300,000. DQB SoCal: $250,000–$400,000. Barcci Builders' Bay Area 2026 data: $350,000–$550,000 for a 600–1,000 sf detached unit. Per-sqft costs flatten around $250–$400 at this size — fixed costs are amortized.
By type and tier
| Type or tier | Range | Notes |
|---|---|---|
| Detached SoCal | $250K–$400K | |
| Detached Bay Area | $350K–$550K | |
| Premium detached (Los Altos/Woodside) | $500K–$700K+ |
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 |
|---|---|---|
| Design & permits | 6–8% | |
| Site work | 5–8% | |
| Foundation | 8–10% | |
| Framing & shell | 15–18% | |
| Roofing | 5–6% | |
| Plumbing | 8–10% | |
| Electrical | 6–8% | |
| HVAC | 3–5% | |
| Insulation & drywall | 6–8% | |
| Kitchen | 8–12% | |
| Bathroom | 5–8% | |
| Flooring | 3–5% | |
| Windows & doors | 4–6% | |
| Exterior siding | 5–7% | |
| Utilities to ADU | 4–6% | |
| Contingency | 10% |
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.
1,000 sq ft ADUs FAQ
- Can I build a 1,000 sq ft ADU on my lot?
- Most California single-family lots allow up to 1,000 sq ft for two-or-more-bedroom ADUs and up to 850 sq ft for studios/one-bedrooms — provided setbacks and lot coverage rules are met (HCD ADU Handbook, March 2026). Some cities allow up to 1,200 sq ft.
- Is a 1,000 sq ft ADU worth the extra cost over 800?
- Often yes. Per-sqft costs are nearly identical at 800 and 1,000 sq ft, but a 1,000 sf two-bedroom commands meaningfully higher rent (often $400–$1,000/month more in CA metros, per DQB and Barcci 2026 data). The rent uplift typically pays back the additional $50K–$100K in build cost within 5–7 years.
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