Complete 2026 cost breakdown: construction, permits, financing, and expected rental ROI.
Calculate your Santa Monica ADU cost →Building an ADU in Santa Monica costs between $250,000-$500,000 for new construction, with per-square-foot costs averaging $325-$550. These figures include design, permitting, site preparation, and construction. The most affordable option is a garage conversion at $140,000-$245,000, while prefab/modular ADUs fall in between at $200,000-$350,000.
| Cost Category | Estimated Range |
|---|---|
| Architectural Plans | $3,000 – $15,000 |
| Permits & Fees | Plan check and building permit fees are valuation-based under the City's adopted fee schedule (finance.smgov.net); Planning charges $985.11 for a deed-restriction application and $833.46 for a Coastal Zone Approval in Concept (fees effective July 1, 2026) |
| Impact Fees | ADUs and JADUs are exempt from the city's Transportation (Ch. 9.66), Parks (Ch. 9.67), Affordable Housing (Ch. 9.64) and Childcare (Ch. 9.65) impact fees (SMMC 9.31.025(O)). Statewide, ADUs 750 sq ft or less and JADUs 500 sq ft or less owe no impact fees (Gov. Code 66311.5); the city warns that ADUs larger than 750 sq ft may owe Public Works (water/wastewater) capital facility fees, and school fees apply above 500 sq ft |
| Site Prep & Foundation | $10,000 – $35,000 |
| Framing & Structure | $15,000 – $45,000 |
| Plumbing | $8,000 – $20,000 |
| Electrical | $5,000 – $15,000 |
| HVAC | $3,000 – $8,000 |
| Interior Finishes | $15,000 – $40,000 |
Quotes for the same ADU commonly vary 20–40% between builders. We pass your request to up to 5 local builders serving Santa Monica, where we have them — free, no obligation.
Get Santa Monica builder quotes →Permit fees in Santa Monica are Plan check and building permit fees are valuation-based under the City's adopted fee schedule (finance.smgov.net); Planning charges $985.11 for a deed-restriction application and $833.46 for a Coastal Zone Approval in Concept (fees effective July 1, 2026). The review timeline is 60 days from a complete application, or the ADU is deemed approved (SMMC 9.31.025(G)); since Jan 1, 2026 the city must also issue a completeness notice within 15 business days (Gov. Code 66317, SB 543). A Coastal Zone CDP runs on its own 60-day clock (Gov. Code 66329), with plan check: Electronic Plan Review: a prescreen for completeness, then routed plan check with corrections issued by email; initial plan review fees are paid at submittal and final fees before issuance. Every ADU needs its own address via an Address Application. Impact fees are ADUs and JADUs are exempt from the city's Transportation (Ch. 9.66), Parks (Ch. 9.67), Affordable Housing (Ch. 9.64) and Childcare (Ch. 9.65) impact fees (SMMC 9.31.025(O)). Statewide, ADUs 750 sq ft or less and JADUs 500 sq ft or less owe no impact fees (Gov. Code 66311.5); the city warns that ADUs larger than 750 sq ft may owe Public Works (water/wastewater) capital facility fees, and school fees apply above 500 sq ft. Pre-approved plans: Preapproved ADU Program under Gov. Code 65852.27 (AB 1332) accepts vendor-submitted Standard ADU Plans for detached ADUs only, with no modifications allowed; as of Sept 2026 the city lists no approved plans ('NONE AT THIS TIME').
| 1-Bedroom Rent | $3,000-$3,700/month |
| 2-Bedroom Rent | $4,000-$4,700/month |
| Annual Rental Income (est.) | $40,200/year |
| Payback Period (est.) | 9.3 years |
| Short-Term Rental | No — ADUs and JADUs may not be rented for 30 days or less (SMMC 9.31.025(M)); the only carve-out is licensed home-sharing under SMMC Ch. |
| Overall ROI Estimate | 5-8% annual return |
A typical ADU in Santa Monica generates approximately $40,200 per year in rental income based on average 1-bedroom rents. At an average construction cost of $375,000, the estimated payback period is 9.3 years — before accounting for the resale value the ADU adds, which an appraiser determines from comparable sales in Santa Monica and varies by market (often less than build cost).
1. Garage conversions save 40-60% vs new construction since the shell already exists. Average cost in Santa Monica: $140,000-$245,000.
2. Prefab/modular ADUs offer predictable pricing and faster timelines. Average: $200,000-$350,000.
3. Pre-approved plans — Santa Monica does not offer a pre-approved/standard ADU plan program yet, so budget for custom architectural plans (typically $3,000-$15,000). See which cities offer pre-approved ADU plans.
4. State grants — California's CalHFA ADU grant (up to $40K) is currently paused; check calhfa.ca.gov/adu for status and your state for active programs.
5. Get multiple bids — ADU contractor pricing varies 20-40% for the same project. We recommend getting at least 3 quotes.
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