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 [32][33][34][35][36][37]
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) | $185,000-$420,000 |
| Cost per Sq Ft | $300-$525 |
| Garage Conversion | $90,000-$185,000 |
| Prefab / Modular ADU (installed) | $120,000-$300,000 |
| City Permit & Plan Review | Planning ADU review is hourly at $217.64 against a $1,500 deposit; building plan check plus inspection is $0.68 + $0.56 per sq ft for a new detached unit ($0.86 + $1.33 for additions and conversions) plus 10% automation fee (Aug 15, 2026 schedules); roughly $2,700-$3,900 all-in for a 750 sq ft ADU |
| Impact Fees | None for an ADU of 750 sq ft or less; larger units pay in proportion to the main house (Gov. Code 66311.5; Irvine DIF ordinance Sec. 2-7-905(F)). Over 750 sq ft the Systems Development Charge (1% of valuation, Muni Code 2-9-601) and the Transportation Corridor Agencies fee ($2,864-$4,030 per multi-family-class unit, FY2027) can apply; the citywide DIF ($5.34 per sq ft) is charged only in the Irvine Business Complex. School fee: IUSD $4.79 per sq ft on the city's 2022 sheet, but the city's form exempts ADUs of 749 sq ft or less |
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: 1,200 sq ft (Gov. Code 66314(d)(5)). An 800 sq ft unit with 4-ft side and rear setbacks must be allowed regardless of lot coverage, floor-area ratio or lot size (66321(b)(3)); the city's checklist (Form 67-01, rev. 1/25) states the same 1,200 and 800 sq ft figures; owner-occupancy: Not required for an ADU (66315). For a JADU, required only if it shares a bathroom with the main house (66333(b), AB 1154, effective Jan 1, 2026); JADUs also need a recorded deed restriction (66333(c)). The city's ADU submittal list still asks every applicant for a notarized, recorded covenant; ask Planning what it covers).
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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 (Planning ADU review is hourly at $217.64 against a $1,500 deposit; building plan check plus inspection is $0.68 + $0.56 per sq ft for a new detached unit ($0.86 + $1.33 for additions and conversions) plus 10% automation fee (Aug 15, 2026 schedules); roughly $2,700-$3,900 all-in for a 750 sq ft ADU), plan check (Building plan check through IrvineReady!, charged per sq ft under Schedule II (Res. 24-41, effective Aug 15, 2026), plus $31.88 permit issuance and state SMIP/energy surcharges; valuation uses the city's ICC table ($175.92 per sq ft, R-3 Type VB, Aug 2026); OCFA reviews the residential site plan (PR160, $398)), and impact fees (None for an ADU of 750 sq ft or less; larger units pay in proportion to the main house (Gov. Code 66311.5; Irvine DIF ordinance Sec. 2-7-905(F)). Over 750 sq ft the Systems Development Charge (1% of valuation, Muni Code 2-9-601) and the Transportation Corridor Agencies fee ($2,864-$4,030 per multi-family-class unit, FY2027) can apply; the citywide DIF ($5.34 per sq ft) is charged only in the Irvine Business Complex. School fee: IUSD $4.79 per sq ft on the city's 2022 sheet, but the city's form exempts ADUs of 749 sq ft or less) are included.
- Permit handling: Confirm they manage Irvine's permit process ("Ministerial. First get the ADU Verification Form signed by Planning (planning@cityofirvine.org, 949-724-6308), then file the Residential ADU application package through the IrvineReady! portal under "For Permitting--Other": building plans, Development Standards Checklist (Form 67-01), Hold Harmless Affidavit, notarized covenant, Developer Deposit Case Set-Up, School Fee, TCA and Address forms, and a C&D waste plan. Plans route to Planning, Public Works, OCFA and C&D review; HOA approval runs separately", typically Completeness check in about 2 business days, then a first plan check target of 20 working days for new construction or 5 for additions and conversions (Bulletin 279); state law requires a decision within 60 days of a complete application or the ADU is deemed approved (Gov. Code 66317)) 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 about 2 business days, then a first plan check target of 20 working days for new construction or 5 for additions and conversions (Bulletin 279); state law requires a decision within 60 days of a complete application or the ADU is deemed approved (Gov. Code 66317)) 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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