What does project info include for an ADU build?

Project info for an ADU typically includes a full budget breakdown covering materials, labor, plans, and permits; a project scope summary detailing the size, layout, and type of unit; and a phase-by-phase construction timeline.

How much does a 600 sq ft ADU typically cost?

Based on real project info from a completed build, a 600 sq ft detached ADU in Southern California costs approximately $307,000–$320,000 at mid-range finishes.

How long does it take to build a detached ADU?

From first design drawing to final inspection, expect approximately five months for a straightforward detached ADU; permit review is typically the longest phase.

What does project info include for an ADU build?

Project info for an ADU typically includes a full budget breakdown covering materials, labor, plans, and permits; a project scope summary detailing the size, layout, and type of unit; and a phase-by-phase construction timeline. It often also includes the contractor's working process and any site-specific requirements such as grading or utility connections.

How much does a 600 sq ft ADU typically cost?

Based on real project info from a completed build, a 600 sq ft detached ADU in Southern California costs approximately $307,000–$320,000 at mid-range finishes. Costs vary by site conditions, local labor rates, and finish selections. Materials and labor represent approximately 94.7% of the total budget.

How long does it take to build a detached ADU?

From first design drawing to final inspection, expect approximately five months for a straightforward detached ADU. The permit phase is typically the longest waiting period at around 60 days. Starting the design and permit process as early as possible is strongly recommended.

Are permits required for a detached ADU?

Yes — permits are always required for a new detached ADU. You will need building, electrical, plumbing, and mechanical permits at a minimum. In California, state law requires local jurisdictions to process ADU permit applications within 60 days.

What is the difference between a detached ADU and an attached ADU?

A detached ADU is a fully separate structure, while an attached ADU shares at least one wall with the primary home. Detached ADUs offer more privacy but are typically more expensive because they require a full independent foundation and separate utility connections.

Can I use an ADU as a rental property?

Yes. In California, ADUs may be rented out for terms of 31 days or longer. A two-bedroom ADU of this size in Southern California can generate between $1,800 and $2,800 per month in rental income depending on location and condition.

How much does it cost to build an ADU in Orange County in 2025?

A complete, all-in ADU in Orange County in 2025 costs: Detached ADU — $240,000 to $490,000 depending on size and finishes. Attached ADU — $185,000 to $380,000. JADU or attached garage conversion — $80,000 to $165,000. Detached garage conversion — $70,000 to $145,000. Per-square-foot construction costs run $280 to $375 for new detached construction. Add $30,000 to $90,000 for soft costs including design, engineering, permits, and utility connections. Any bid significantly below these ranges is omitting major cost categories.

What is the cost per square foot to build an ADU in Southern California?

In 2025, ADU construction costs per square foot in Southern California: Orange County — $280 to $375 per sq ft for new detached construction; $150 to $220 per sq ft for garage conversion. Western LA County — $265 to $360 per sq ft new construction. Western Riverside County (Corona, Norco, Jurupa Valley) — $250 to $340 per sq ft new construction. These are hard construction costs only. Add $30,000 to $90,000 in soft costs (design, permits, utility connections) to arrive at the true all-in project cost.

What soft costs should I budget for an ADU in California?

ADU soft costs in Orange County typically run $30,000 to $90,000 for a full-size detached ADU and include: architectural design and drafting ($6,000–$14,000), structural engineering ($3,500–$8,000), Title 24 energy report ($1,200–$2,500), city building permit fees ($6,000–$22,000), school impact fees (varies — waived under 750 sq ft), water meter application and connection ($4,000–$15,000), sewer capacity fee ($2,000–$8,000), electrical service extension ($2,000–$6,000), and geotechnical report if required ($2,500–$6,000). Soft costs are frequently omitted from low contractor bids.

How much do ADU permit fees cost in Orange County cities?

ADU permit fees in Orange County vary significantly by city: Anaheim — $6,000–$11,000; Irvine — $12,000–$22,000; Huntington Beach — $8,000–$15,000; Garden Grove — $5,000–$9,000; Santa Ana — $6,000–$10,000; Newport Beach — $14,000–$25,000+; Costa Mesa — $7,000–$13,000; Fullerton — $7,000–$12,000. These are permit fees only and do not include utility connection fees, school impact fees, or engineering costs. Water meter and sewer connection fees are the largest variable — adding $8,000–$28,000 depending on city and utility district.

Does a garage conversion ADU cost less than a detached ADU?

Yes — significantly less. A detached garage conversion in Orange County costs $70,000 to $145,000 all-in, compared to $240,000 to $490,000 for a new detached ADU. The savings come from using the existing structural shell (foundation, framing, roof) rather than building new. However, the conversion still requires full plumbing, electrical upgrade, HVAC, insulation, interior finish, permits, and utility connections — which is why bids below $65,000 for a complete garage conversion ADU are typically missing major cost categories.

What hidden costs do most ADU contractor bids leave out?

The most commonly omitted costs from low ADU contractor bids in Southern California: (1) Utility connection fees — water meter, sewer capacity, electrical service ($8,000–$28,000); (2) School impact fees for ADUs over 750 sq ft ($3,000–$8,000 depending on district); (3) Soils/geotechnical report for required sites ($2,500–$6,000); (4) Construction contingency for underground discoveries (budget 10–15%); (5) Landscape restoration after construction ($3,000–$8,000); (6) Title 24 energy report ($1,200–$2,500); (7) HOA architectural review fees in planned communities ($500–$3,000). Always request a complete, line-item all-in proposal before signing any contract.

How much does an ADU increase property value in Orange County?

In Orange County, a permitted, well-built ADU increases overall property value by approximately $250,000 to $400,000 for a full-size (1,000–1,200 sq ft) detached ADU. Smaller ADUs and garage conversions add $100,000 to $250,000 depending on size, quality, and location. In most cases, the ADU adds more value than its construction cost — particularly in high-demand OC cities like Irvine, Huntington Beach, and Newport Beach where rental income capitalization rates drive appraisal values above cost.

What is the payback period for an ADU investment in Southern California?

The cash-on-cash payback period for an ADU in Orange County ranges from 8 to 18 years depending on ADU type, project cost, and rental income. A garage conversion ADU at $110,000 generating $1,800/month nets approximately $20,000/year after expenses — a 5.5-year payback. A $350,000 detached 2BR ADU generating $3,000/month nets approximately $28,000/year after expenses — a 12.5-year payback. When equity appreciation is included, effective payback periods are often 4–8 years because the ADU typically appreciates at the same rate as the surrounding market.