An ADU builder in Irvine is a licensed contractor who designs and constructs accessory dwelling units — detached backyard units, garage conversions, attached additions, and junior ADUs (JADUs). Because an ADU is a complete second dwelling, the builder coordinates foundation, framing, plumbing, electrical, and HVAC work and pulls it through Irvine's permit process and utility connections. Not every general contractor has built one, so the right builder is one with ADU-specific experience in California.
What ADU Builders Cost in Irvine [6][7]
Based on our Irvine cost data, expect the following ranges from local ADU builders. Quotes for the same scope typically vary 20-40% between contractors, so getting at least three bids is the single best way to control cost.
| New Detached ADU (all-in) | $180,000-$420,000 |
| Cost per Sq Ft | $315-$525 |
| Garage Conversion | $90,000-$150,000 |
| Prefab / Modular ADU (installed) | $120,000-$300,000 |
| City Permit & Plan Review | Deposit-based (Developer Deposit Case Set-Up) — confirm current amounts with Irvine Community Development, 949-724-6308. School fees apply to ADUs of 500 sq ft or more (School Fee Determination Form required) |
| Impact Fees | Waived for ADUs under 750 sq ft (state law); larger units charged proportionally — confirm with the Building & Safety Division |
For a full line-item breakdown, see our Irvine ADU cost guide. To confirm what you're allowed to build before you hire, review the Irvine ADU rules (max detached size: Up to 1,200 sq ft; 800 sq ft ADU must be allowed on virtually any lot. HCD struck Irvine's lot-size-based ADU size caps; owner-occupancy: Not required for ADUs (AB 976). JADUs require owner occupancy unless the JADU has its own full bathroom (AB 1154, 2026). Note: HCD's Jan/Mar 2025 letters faulted Irvine for requiring deed restrictions on standard ADUs).
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How to Vet an ADU Builder in Irvine
- License: Confirm a current contractor's license in California and that it's in good standing. Ask for the license number and verify it with the state board.
- ADU-specific experience: Ask how many ADUs they've completed in or near Irvine and request addresses or photos. ADU permitting and setbacks differ from a kitchen remodel.
- Portfolio & references: Get references from recent ADU clients and, if possible, visit a finished unit.
- Insurance: Verify general liability and workers' compensation coverage. Ask for a certificate of insurance.
- Written, detailed bid: Insist on an itemized, fixed-price or clearly-scoped bid — not a verbal estimate. It should state whether permits (Deposit-based (Developer Deposit Case Set-Up) — confirm current amounts with Irvine Community Development, 949-724-6308. School fees apply to ADUs of 500 sq ft or more (School Fee Determination Form required)), plan check (Building plan check through IrvineReady! portal; fees deposit-based — confirm with city), and impact fees (Waived for ADUs under 750 sq ft (state law); larger units charged proportionally — confirm with the Building & Safety Division) are included.
- Permit handling: Confirm they manage Irvine's permit process ("Ministerial review. Submit ADU Verification Form (planning@cityofirvine.org) + ADU Permit Application, Development Standards Checklist, Hold Harmless Affidavit, notarized covenant, School Fee Determination Form, and TCA form via the IrvineReady! online permit portal", typically Completeness check in ~2 business days; state law requires approval or denial within 60 days with deemed-approved remedy (SB 543, 2026). Plan realistically for 2-4 months submittal-to-permit) and who is responsible if revisions are required.
- Payment schedule: Avoid large upfront payments. A reasonable schedule ties payments to completed milestones.
Questions to Ask Before You Hire
- How many ADUs have you built in Irvine in the last two years?
- Is your bid fixed-price, and what would trigger a change order?
- Are permits, plan check, and utility connection fees included?
- What's a realistic timeline, including permit review (Completeness check in ~2 business days; state law requires approval or denial within 60 days with deemed-approved remedy (SB 543, 2026). Plan realistically for 2-4 months submittal-to-permit) and construction?
- Who is my point of contact and how are delays communicated?
- What warranty do you provide on workmanship?
- Can you share three recent California ADU client references?
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