Use this checklist to stay organized from first research through move-in day. Each item maps to a chapter in our full Stress-Free Guide to Building an ADU in California — download it free at aduhomeconstruction.com for detailed guidance on every step.
$150–$450KTypical ADU cost range
$1,800–$3,500Monthly rental income
15 daysSB 543 permit review
$40KCalHFA grant (if eligible)
1
Determine Your ADU Type & Goals
- Clarify your goal: rental income, family housing, home office, or property value increase
- Understand ADU types: Detached, Attached, Garage Conversion, JADU (up to 500 sq ft within existing home), or Prefab/Modular
- Check your lot size and existing structures for feasibility
- Research your city's specific ADU ordinance (setbacks, height, parking)
- Determine if your property is in an HOA — California law limits but doesn't eliminate HOA restrictions on ADUs
Pro Tip: JADUs (Junior ADUs) are the fastest and cheapest path — they use existing space within your home and have a streamlined permit process.
2
Budget & Financing
- Estimate total project cost (2026 averages: Detached $200–$450K, Attached $150–$300K, Conversion $80–$180K, JADU $50–$100K)
- Add 10–15% contingency buffer for unexpected costs
- Check CalHFA ADU Grant eligibility (up to $40,000 for qualifying homeowners)
- Explore financing: HELOC, home equity loan, construction loan, or cash-out refinance
- Calculate projected rental income vs. monthly costs (mortgage, insurance, utilities)
- Budget for permit fees ($1,000–$5,000+), utility connections ($5,000–$15,000), and impact fees (if applicable)
Pro Tip: Under SB 13 (extended through 2025, check 2026 status), impact fees are waived for ADUs under 750 sq ft. Verify current fee waivers with your city.
3
Design & Planning
- Decide on size (most ADUs: 400–1,200 sq ft) based on lot and intended use
- Hire an architect or use pre-approved ADU plans (many cities offer free standard plans)
- Plan layout: bedrooms, bathroom(s), kitchen, storage, laundry hookups
- Consider accessibility: aging-in-place features, ADA compliance, single-story design
- Plan utility connections: sewer/septic, water, electrical, gas (if applicable)
- Energy efficiency: plan for Title 24 compliance, consider solar, efficient HVAC, insulation
Pro Tip: Pre-approved plans from your city save 2–4 weeks on permit review and $3,000–$8,000 in architect fees.
4
Permits & Approvals (2026 Updates)
- Submit permit application to your local building department
- Know your rights under SB 543: cities must complete permit review within 15 days (down from 60)
- Prepare required documents: site plan, floor plan, structural drawings, Title 24 energy calcs
- Check if your property needs any special reviews (coastal zone, historic district, fire hazard area)
- Note AB 462: new side-yard ADU provisions for specific lot types
- Pay permit fees and schedule initial inspections
Pro Tip: SB 543 (effective 2026) slashes the permit review timeline to 15 days. If your city misses this deadline, your application may be deemed approved. Know the law — it's your leverage.
5
Hire Your Team & Build
- Get 3+ bids from licensed, insured general contractors with ADU experience
- Verify contractor license at cslb.ca.gov (California State License Board)
- Review and sign a detailed construction contract (scope, timeline, payment schedule, change order process)
- Establish communication cadence: weekly progress updates, site visits
- Monitor construction phases: foundation → framing → rough-in (MEP) → insulation → drywall → finishes
- Schedule and pass all required inspections (foundation, framing, electrical, plumbing, final)
Pro Tip: Never pay more than 10% upfront. Structure payments around completed milestones, with final payment held until Certificate of Occupancy is issued.
6
Final Inspections & Occupancy
- Complete all punch-list items before final inspection
- Pass final building inspection
- Obtain Certificate of Occupancy from your city
- Set up separate utility meters/accounts (if required)
- Get landlord insurance or update homeowner's policy for rental use
- Register ADU as rental unit with your city (if required)
7
Optimize & Maximize Value
- Research local rental comps to set competitive rent pricing
- Consider short-term rental (Airbnb) vs. long-term tenant — check local STR regulations
- Claim IRA Section 45L energy credits (up to 30% for qualifying energy-efficient construction through 2032)
- Document all construction costs for tax depreciation benefits
- Get a post-construction appraisal to document increased property value
- Create a maintenance schedule for your ADU (HVAC, roof, plumbing, exterior)
Pro Tip: ADUs typically add 20–30% to property value. A $200K ADU build on a $700K property could push your home value to $900K+.
Want the Full Guide?
This checklist covers the essentials. Our free 34-page Stress-Free Guide to Building an ADU in California goes deep on every step — with cost breakdowns, financing strategies, 2026 law updates, and infographics.
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