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AfterHow Much Does ADU Construction Cost in San Diego?
ADU construction in San Diego typically costs between $106,200 and $259,600 for a complete accessory dwelling unit in 2026. Most homeowners building a standard 500-800 square foot one-bedroom ADU in neighborhoods like North Park, Clairemont, and Rancho Bernardo spend between $165,000 and $210,000 from permit to final paint. A detached unit with a full kitchen and bathroom runs higher than a garage conversion, while a junior ADU (JADU) inside the existing home footprint can land below the range.
These figures come from what we see on real bids and completed projects across San Diego County in 2026, not national averages. Your final number depends on site conditions, utility connections, foundation work, and the finish level you choose. Call (619) 673-9302 for a written price on your specific property. We deliver a fixed number before any work starts, no vague estimates that grow on the final bill.
ADU Construction Cost Breakdown (2026)
Here’s where the money goes on a typical detached ADU in San Diego. These are real line-item ranges we see across completed projects in 2026, from a 400-square-foot studio in Lemon Grove to a 1,000-square-foot two-bedroom unit in La Jolla.
| Line Item | San Diego Price Range (2026) |
|---|---|
| Design & Architectural Plans | $6,000 – $18,000 |
| City Permits & Impact Fees | $8,000 – $35,000 |
| Site Preparation & Grading | $4,000 – $15,000 |
| Foundation (slab or raised) | $12,000 – $35,000 |
| Framing & Shell | $25,000 – $55,000 |
| Roofing | $7,000 – $18,000 |
| Plumbing (rough-in + fixtures) | $10,000 – $28,000 |
| Electrical (panel, wiring, fixtures) | $8,000 – $22,000 |
| HVAC / Mini-Split System | $4,000 – $12,000 |
| Insulation & Drywall | $6,000 – $14,000 |
| Kitchen (cabinets, counters, appliances) | $12,000 – $35,000 |
| Bathroom (full) | $10,000 – $28,000 |
| Flooring | $3,500 – $12,000 |
| Paint & Finish Work | $3,000 – $9,000 |
| Doors, Windows & Trim | $4,000 – $14,000 |
That’s a lot of line items, but they don’t all hit the high end at once. A basic 500-square-foot ADU with builder-grade finishes in El Cajon or Chula Vista can land near the bottom of each range. A 900-square-foot two-bedroom with a Cambria quartz countertop, Kohler bath fixtures, and KraftMaid cabinetry in Del Cerro or Point Loma pushes toward the top.
Two big cost drivers specific to San Diego: slope and soil. Canyon-adjacent lots in areas like Mission Hills, Bankers Hill, and parts of Mount Helix often need caissons or retaining work before a foundation goes in. That can add $15,000 to $50,000 to the total. Flat inland lots in Scripps Ranch or Mira Mesa typically skip that entirely.
The second driver is utility distance. Running a separate electrical meter, water line, and sewer connection from the street to a detached ADU at the back of a deep lot in Rancho Peñasquitos costs more than a garage conversion in Normal Heights where the utilities already stub into the existing structure.
What Affects ADU Construction Pricing in San Diego
Five factors move the number more than anything else we see on ADU estimates across San Diego County:
- Detached vs. attached vs. garage conversion. A detached ADU starts at a higher base because it needs its own foundation, roof, and four exterior walls. A garage conversion in areas like San Diego ADU construction typically runs $35,400 to $94,400 because the shell already exists. An attached addition with direct access to existing utilities often splits the difference.
- Site conditions and slope. San Diego’s terrain varies hard. A flat lot in Kearny Mesa builds fast. A hillside lot in La Mesa or Tierrasanta with a 30-degree grade requires retaining walls, pier drilling, or engineered footings. That’s real money, not a line item to wave away.
- Utility connections and meter separation. If you want the ADU metered separately for rental income, SDG&E work plus trenching for water and sewer can add $10,000 to $30,000. If you share the main panel and run a subpanel, the cost drops but you give up separate billing.
- Finish level. Builder-grade cabinets and laminate counters keep the kitchen around $12,000. Specification-grade materials from our partnerships with KraftMaid, Wellborn, Cambria, and Silestone can double that. The same spread applies to bathrooms: a standard tub-shower versus a Kohler or Toto walk-in with tile to the ceiling.
- Permit and fee timing. San Diego’s Development Services Department (DSD) has streamlined ADU permits, but impact fees still land between $8,000 and $35,000 depending on the unit size, school district fees, and whether you’re in the city of San Diego proper or an incorporated city like Chula Vista, Oceanside, or Escondido. These fees moved in 2026 and they move again. We price them current at the time of your home improvement estimate.
How to Save on ADU Construction
We believe the best way to save is to know the full number before you commit. That’s why Mason Remodeling Co San Diego delivers a written price before any work starts, on every ADU project, every time. No verbal ranges that drift upward after demolition. No surprise invoices at the end. You get a fixed number in writing.
Beyond pricing transparency, here’s what actually reduces the total in 2026:
- Start with a garage conversion if you have an underused one. The shell, roof, and often the slab are already there. That’s $60,000 to $100,000 less than a detached build in most San Diego neighborhoods. We’ve converted garages in Normal Heights, North Park, and City Heights that turned into beautiful one-bedroom rentals.
- Keep the footprint under 750 square feet. San Diego allows ADUs up to 1,200 square feet on most residential lots, but the cost per square foot actually climbs after about 800 because you add structural spans, more HVAC, and longer utility runs. A tight 600-square-foot one-bedroom delivers 90% of the rental value at 70% of the cost of a 1,000-square-foot two-bedroom.
- Choose doors and windows from standard sizes. Custom opening sizes add framing time, material cost, and sometimes engineering. Standard off-the-shelf sizes from our window partners keep both the schedule and the invoice smaller.
- Build the kitchen along one wall. A galley or single-wall kitchen cuts plumbing runs, countertop square footage, and cabinet count compared to an island layout. You can still get Cambria counters and Kohler fixtures without the island markup.
- Ask about phasing the exterior. Some San Diego homeowners choose to rough-in the ADU shell now, pass inspection, and finish interiors in a later phase. That spreads the cash outlay. We’ll quote both ways and give you the line items for each phase. Call (619) 673-9302 and ask for a phasing estimate.
ADU Construction Cost per Square Foot in San Diego
San Diego ADUs in 2026 run between $212 and $520 per square foot depending on finish level, site work, and whether the unit is detached or a conversion. On the low end, a simple garage conversion in Chula Vista with builder-grade finishes can land near $212 per square foot. On the high end, a custom detached unit in Coronado or La Jolla with site retaining and premium finishes hits $500+.
Here’s how that plays out at common sizes:
- 400 sq ft studio: $85,000 – $145,000 total
- 600 sq ft one-bedroom: $127,000 – $195,000 total
- 800 sq ft two-bedroom: $170,000 – $260,000 total
- 1,000 sq ft two-bedroom with garage: $212,000 – $330,000 total
These are turnkey numbers, including permits, utilities, finishes, and the written guarantee. Isaac Pruett, who leads Mason Remodeling Co San Diego, has been pricing ADUs in this market since 2004 and can tell you within one conversation which side of the range your property falls on.
San Diego ADU Permits and Fees: What to Expect in 2026
Permitting in the city of San Diego runs through the Development Services Department, and ADUs have a faster path than full additions under state law. But faster doesn’t mean free. Expect these categories on your estimate:
- Plan check and building permit fees: $2,500 – $8,000 depending on unit size and whether structural or geotech review is required.
- School impact fees: $3,000 – $12,000. These apply to ADUs over 500 square feet in most San Diego districts and fund local school capacity.
- Utility connection and meter fees: $2,000 – $15,000. A separate SDG&E meter, water main tap, and sewer lateral each carry their own fee schedule.
- Fire sprinkler requirements: $3,000 – $10,000 if your ADU triggers a sprinkler mandate. Detached units under 500 square feet sometimes avoid this; we check the current code on your exact address.
In incorporated cities like Oceanside, El Cajon, or Poway, fee structures differ. We’ve pulled permits across every municipality in the county and we price them as they exist at the moment of your written estimate, not as they existed a year ago.
ADU Construction Timeline in San Diego
A standard detached ADU takes 5 to 9 months from design approval to final inspection in San Diego County in 2026. Garage conversions run shorter, typically 3 to 5 months. Here’s the flow:
- Design and plan approval: 4-8 weeks. This includes architectural drawings, structural calculations, and DSD submittal.
- Permit issuance: 2-6 weeks depending on the municipality and whether corrections come back from plan check.
- Site work and foundation: 2-5 weeks. Slower on hillside lots in La Mesa or Tierrasanta where drilling and retaining enter the picture.
- Framing, roofing, and rough-in: 6-10 weeks. This is where inspections happen and the structure takes shape.
- Finishes and final inspection: 6-10 weeks. Cabinetry, tile, flooring, paint, and the final walkthrough with the inspector.
Weather delays in San Diego are rare compared to other markets, but marine layer mornings in coastal areas like Ocean Beach and Pacific Beach can slow exterior paint and stucco cure times by a few days. We build that into the schedule and tell you up front.
FAQs – ADU Construction Cost
How much does a garage conversion ADU cost in San Diego?
A garage conversion ADU in San Diego costs $35,400 to $94,400 in 2026. The range covers everything from a basic 300-square-foot studio conversion to a 500-square-foot one-bedroom with a full kitchen and bath. Your final number depends on whether the garage slab is in good shape, how far utilities need to run, and the finish level you choose. Call (619) 673-9302 for a written price on your specific garage.
Is it cheaper to build an ADU or add on to the main house?
An ADU is almost always cheaper per square foot than a fully integrated home addition. ADU construction in San Diego runs $106,200 to $259,600 compared to $53,100 to $153,400 for a typical attached home addition, but the addition often adds square footage to your main living space and appraises differently. For pure rental income and speed, the ADU wins. For resale value and daily use, the addition often wins. We’ll price both against each other on your property so you can compare real numbers.
Can you build an ADU for under $100,000 in San Diego?
Yes, in specific circumstances. A JADU (junior ADU) inside your existing home footprint, such as a converted bedroom with its own entrance and kitchenette, can often be built for $60,000 to $95,000 because there’s no new foundation, shell, or utility tap. A small garage conversion with basic finishes can also land near $90,000. A detached unit under $100,000 is difficult in 2026 San Diego unless you’re doing substantial work yourself.
How long does ADU construction take in San Diego?
Plan on 5 to 9 months for a detached ADU and 3 to 5 months for a garage conversion in San Diego in 2026. Most of the variation comes from permit turnaround, plan check corrections, and weather-sensitive exterior work in coastal areas. We give you a written schedule alongside your written price, so you know the timeline before we break ground.
Do I need a separate meter for my San Diego ADU?
Not always. You can run a subpanel off your main electrical service and save the $2,000 to $8,000 that a separate SDG&E meter and connection typically costs. However, if you plan to rent the ADU and bill tenants separately, a dedicated meter is worth the investment. Water and sewer connections generally tap off the main house, though some deep-lot ADUs in areas like Rancho Bernardo and Scripps Ranch need a new lateral that adds $3,000 to $12,000. We’ll show you both options on the written estimate.
What does ADU construction include in the price?
Our ADU price includes design, permits, all site work, foundation, framing, roofing, plumbing, electrical, HVAC, insulation, drywall, kitchen and bath finishes, flooring, paint, and the written guarantee. It does not include furniture, window coverings, landscaping beyond grade, or appliances unless you ask us to source them. You’ll see every line item, every allowance, and every fixed cost in writing before a single tool is unpacked.
Why Choose Mason Remodeling Co San Diego for Your ADU
We’re part of the Threshold Group family of home-service companies, founded in 2004. That means every ADU project follows The Threshold Standard: every crew member is background-checked, identity-verified, and introduced to you by name and photo before they arrive. They show up in a clean marked uniform, badge at the door, and they know exactly what’s on the work order for the day.
Isaac Pruett leads our San Diego team in general contracting, bathroom remodeling, whole-home remodels, and ADU construction. He’s priced and built ADUs across this county for two decades, from garage conversions in City Heights to detached two-bedrooms in Poway.
Every project gets a written price before any work starts. That’s not a promotion and it’s never waived. Every completed project carries a written guarantee with clear terms: 365 days from the completion date, if the work is not right, we make it right at no cost to you. And if a repair or installation fails, our free return visit policy means no charge, no dispute process, no conditions.
A live person answers our phones 24 hours a day, 7 days a week, including weekends and holidays. No call trees. No voicemail loops. You call, a person picks up.
Ready to get a real number for your ADU project in San Diego? Call (619) 673-9302 today for a free estimate and a written price. We’ll walk your property, answer your questions, and hand you a fixed number before you commit to anything.
Pricing reflects the San Diego market as of 2026. Mason Remodeling Co San Diego offers free estimates – call (619) 673-9302.
Written by Isaac Pruett, Owner at Mason Remodeling Co San Diego, serving San Diego since 2004.
What Our Customers Say
"Opened up the wall between kitchen and dining room. They handled the beam and permit and the floor transitions look seamless."
- Wendy A."Good work on the hall bath. They found a rotted subfloor, which added cost, but showed me photos and a clear price first."
- Neil P."Bathroom gut job. Replaced the old tub with a walk-in shower and added a niche. Waterproofing was done properly with a flood test before tile."
- Greg L.
