A free site visit, a check of what your lot allows and a written, line-item price.
Get your free estimateHow Much Does Junior ADU & Interior Conversion Cost in San Diego?
A Junior ADU (JADU) and interior conversion in San Diego typically costs between $68,000 and $145,000 for a full build-out in 2026, with most homeowners landing around $95,000 to $115,000 for a permitted conversion of an existing attached space. A simpler JADU carved out of existing square footage inside the primary home, like an attached garage-to-bedroom conversion, can run as low as $45,000 when the plumbing is already nearby. The single biggest cost driver is whether you’re converting space that already exists inside your home’s footprint or adding new square footage, since new construction in San Diego runs $280 to $420 per square foot depending on site conditions.
These numbers come from what we see on real projects across San Diego County, from Chula Vista to Oceanside to El Cajon, and they reflect current 2026 permit, labor, and material costs. If you want a written price for your specific property, call (619) 376-2760 and we’ll walk the site and put a number in front of you before any work starts.
Key Takeaways:
- Typical Junior ADU / interior conversion in San Diego: $68,000 – $145,000 in 2026
- Simple JADU within existing home footprint: $45,000 – $80,000
- Garage conversion to full ADU with kitchen and bath: $95,000 – $160,000
- Permit and impact fees in the City of San Diego run $2,800 – $7,500 for most JADU projects
- Most projects complete in 10 – 16 weeks from permit to final inspection
- Lodgewick gives a written price before work begins – every time, no exceptions
Junior ADU & Interior Conversion Cost Breakdown (2026)
Here’s how the numbers break down line by line for a typical Junior ADU project in San Diego. These are real ranges based on local labor rates in the San Diego market, which run 15 – 25% higher than the national average due to coastal construction costs and local wage standards.
| Cost Item | Typical Range (San Diego, 2026) | What It Includes |
|---|---|---|
| Design and architectural plans | $3,500 – $9,500 | Site survey, floor plan, structural drawings, Title 24 energy calcs |
| City of San Diego permits and impact fees | $2,800 – $7,500 | Building permit, plan check, school fees (waived for JADUs under 500 sq ft in many cases), sewer and water connection fees |
| Demolition and site prep (interior conversion) | $3,000 – $8,000 | Removing walls, flooring, existing fixtures, debris hauling from Mission Valley or wherever your project is |
| Framing and drywall | $8,000 – $18,000 | New partition walls, ceiling work, insulation, drywall installation and texture |
| Plumbing rough-in and fixtures | $7,000 – $15,000 | Tying into existing water and sewer lines, new bathroom or kitchenette sink, water heater connection if needed |
| Electrical work | $6,000 – $14,000 | New circuits, panel upgrade if your existing panel is maxed out, lighting, outlets, subpanel installation |
| Flooring | $3,500 – $9,000 | LVP, tile, or engineered wood across 400 – 600 sq ft of finished floor |
| Kitchenette / wet bar (if included) | $6,000 – $18,000 | Countertop, sink, base cabinets, refrigerator rough-in, small appliance circuits |
| Bathroom build-out | $12,000 – $28,000 | Shower or tub, toilet, vanity, tile surround, exhaust fan, waterproofing |
| Windows and doors | $4,000 – $12,000 | Egress window if converting a garage, exterior door, interior door hardware |
| HVAC and ventilation | $5,000 – $12,000 | Ductless mini-split, bathroom fan, kitchen exhaust, air sealing |
| Paint and finish work | $3,000 – $7,000 | Primer and two coats on walls and trim, caulking, touch-ups |
| General contractor fee and project management | $8,000 – $18,000 | Scheduling, subcontractor coordination, inspections, warranty paperwork |
| Total (typical JADU, 400 – 600 sq ft) | $68,000 – $145,000 | Turnkey, permitted, inspected, and covered by written guarantee |
That total range assumes you’re working with an existing space attached to your home. In neighborhoods like North Park, Normal Heights, or Clairemont where homes were built from the 1920s through the 1960s, hidden conditions like knob-and-tube wiring, cast-iron drain lines, or unpermitted previous work can push the number toward the top of that range or beyond. We’ve seen projects in older San Diego neighborhoods where the electrical panel replacement alone added $4,500 because the existing panel was a 60-amp unit from the Eisenhower administration.
What we don’t do is give you a number, then change it at the door. The Kingswell Guarantee means you get a written price before work starts, and that price doesn’t move unless you change the scope. That promise is delivered in writing on every project we take on.
What About Full Garage Conversions vs. Interior JADUs?
A garage conversion in San Diego costs more than a JADU carved out of interior space, typically $95,000 to $160,000, because you’re dealing with a concrete slab that usually needs insulation and vapor barrier work, the garage door has to come out and get replaced with a wall and windows, and the existing electrical service to a detached or attached garage is often minimal. A true interior conversion, where you’re sectioning off an existing bedroom wing or bonus room, runs lower because the structure, roofing, and foundation are already done.
For a deeper look at how JADUs differ from full ADUs and which path makes sense on your lot, see our Junior ADU & Interior Conversion service page. It walks through the San Diego zoning rules that determine what you can build on your specific property.
What Affects Junior ADU & Interior Conversion Pricing in San Diego
- Location within San Diego County. The City of San Diego’s permit fees are lower than some incorporated cities. Del Mar and Solana Beach have their own fee schedules, and projects there routinely carry $1,500 – $3,000 more in plan-check and inspection costs than a comparable project in the city proper. Coastal zones add setbacks and view-corridor requirements that can force design changes.
- Age of your home and its existing systems. Homes built before 1970 in neighborhoods like Mission Hills, Kensington, and South Park frequently have galvanized steel plumbing and undersized electrical panels. If your 100-amp panel can’t handle the new load, you’re adding $3,500 – $6,500 for an upgrade to 200 amps with a new meter main.
- Proximity of existing plumbing and sewer lines. If the space you’re converting is on the opposite side of the house from the main drain line, running new waste pipe through a slab or crawlspace can add $4,000 – $9,000. Homes on raised foundations (common in older San Diego neighborhoods) are cheaper to plumb than slab-on-grade homes.
- Whether you need a separate entrance. A JADU by California law can share the home’s main entrance, but many San Diego homeowners want a private exterior door for the unit. Cutting a new exterior door opening and adding a small landing or steps runs $2,500 – $5,000 including weatherproofing and flashing.
- Finish level and material choices. Builder-grade finishes on a 500-square-foot JADU run about $15,000 – $20,000 for flooring, countertops, cabinets, and fixtures combined. Moving to mid-range finishes from names like James Hardie for exterior siding or better-grade cabinetry pushes that to $25,000 – $35,000. We work with James Hardie materials regularly because they hold up in San Diego’s salt air near the coast better than most alternatives.
- Access and site conditions. If your home is on a steep lot in University Heights or La Mesa with no street parking for a dumpster or material delivery, expect to pay $1,000 – $2,500 extra for hauling and logistics. Tight back-alley access behind homes in Barrio Logan or Logan Heights creates the same issue.
How to Save on Junior ADU & Interior Conversion
You can hold down costs without cutting corners. Here’s what actually works in the San Diego market:
- Keep the JADU within existing square footage. California law allows a Junior ADU up to 500 square feet to be created entirely within the existing walls of your primary home. No foundation, no roof work, no major structural changes. This is the single biggest money saver, often cutting $20,000 – $40,000 off a project compared to adding new space.
- Position the kitchenette or bathroom near existing plumbing. If you can put the JADU’s wet areas on a wall that backs up to an existing bathroom or laundry room, you’ll avoid long sanitary line runs and the associated cost. We always look at this first when we walk a site.
- Use the state’s JADU permit fee waivers. The City of San Diego has waived or reduced impact fees for accessory dwelling units under 750 square feet since 2020, and JADUs under 500 square feet are exempt from many school and park fees. Confirm the current status with the Development Services Department, but expect to save $2,000 – $4,000 on a typical JADU.
- Choose a direct-entry door over adding square footage. If privacy is your concern, a simple new exterior door in an existing wall is far cheaper than bumping out the footprint. Save the bump-out budget for something else.
- Get a written, fixed price. This matters more than most homeowners realize. A price that changes mid-project is a hidden cost. Lodgewick’s written price is delivered before work begins, stays fixed unless you change the scope, and is backed by the 365-Day Done Right Promise: if the work isn’t right, we come back and make it right, on our dime, within the guarantee period. That’s in writing on every project.
For a free estimate on your specific San Diego property, call (619) 376-2760. A live person answers, 24 hours a day. You won’t get a voicemail loop.
FAQs – Junior ADU & Interior Conversion Cost
How much does a Junior ADU cost in San Diego in 2026?
A Junior ADU in San Diego typically costs $68,000 to $145,000 for a turnkey conversion of existing attached space, including permits, design, construction, and finishes. Simple projects under 400 square feet with modest finishes can land around $45,000 to $65,000. The City of San Diego waives many impact fees for JADUs under 500 square feet, which helps keep the number lower than a full detached ADU. For an exact written price on your property, call (619) 376-2760 – estimates are free and the price is in writing before anything starts.
What is the difference between a Junior ADU and a standard ADU?
A Junior ADU is a dwelling unit of 500 square feet or less created within the existing walls of a single-family home, while a standard ADU can be larger, detached, or attached as new construction. JADUs in California may share a bathroom or kitchen with the main house, though most San Diego homeowners add a private bathroom. The cost difference is significant: a JADU runs $68,000 – $145,000, while a detached ADU in San Diego typically runs $180,000 – $350,000. That’s the JADU’s main appeal: you get a rentable or family unit for roughly half the cost of a detached build. Call (619) 376-2760 for a free site walk and a written number for your specific property.
Can you convert my garage into a Junior ADU in San Diego?
Yes, an attached garage conversion in San Diego costs $95,000 to $160,000 depending on the garage’s condition, access to plumbing, and whether the slab needs insulation and leveling work. Detached garage conversions run higher, $120,000 to $180,000, because you’re also dealing with running new utility lines from the main house. The City of San Diego has a pre-approved ADU plan program that can shave $3,000 to $6,000 off design costs if your garage matches one of the standard layouts, though most conversions need custom drawings. Lodgewick handles garage conversions regularly throughout San Diego County – call (619) 376-2760 and we’ll tell you whether your specific garage is a good candidate, at no cost.
How long does a Junior ADU or interior conversion take in San Diego?
Most JADU and interior conversion projects in San Diego take 10 to 16 weeks from the day permits are submitted to the day of final inspection. Plan check at the City of San Diego’s Development Services Department typically adds 3 to 6 weeks before construction begins, so total timeline from signed contract to move-in is usually 4 to 5 months. Larger projects with structural changes or utility trenching can extend toward 6 months. Lodgewick’s written price includes a defined timeline, and our crews show up in the arrival window we give you – it’s part of The Kingswell Guarantee. Call (619) 376-2760 to get a project timeline for your specific property.
Is it cheaper to do an interior conversion than to build a detached ADU?
Yes, an interior conversion or JADU is $100,000 to $200,000 cheaper than building a detached ADU in San Diego, because you’re not paying for foundation work, new roof structure, new utility trenching, or new exterior walls. A typical attached JADU runs $68,000 – $145,000, while a detached ADU of similar size runs $180,000 – $350,000. The trade-off is square footage and privacy: a JADU is capped at 500 square feet and is attached to your home. For many San Diego homeowners who want rental income or space for an aging parent, the JADU is the clear financial winner. Call (619) 376-2760 for a free estimate – we’ll show you both options side by side with real numbers for your lot.
Do I need permits for a Junior ADU in San Diego?
Yes, a Junior ADU in San Diego requires a building permit from the City of San Diego’s Development Services Department, and the permitting cost is typically $2,800 to $7,500 including plan check and impact fees. Unpermitted conversions are a problem when you go to sell, refinance, or make an insurance claim, and San Diego’s code enforcement has gotten more active on unpermitted dwelling units since 2021. Lodgewick handles the entire permit process for you – drawings, submittals, plan check responses, inspections – and it’s included in the written price. Call (619) 376-2760 for a free consultation on your specific property.
Does Lodgewick work with prefab ADU manufacturers in San Diego?
Yes. We have hands-on experience with leading prefab and panelized ADU systems including Abodu, Cover, Dvele, Mighty Buildings, Boxabl, Plant Prefab, and Tuff Shed, and we match the right system to your lot, budget, and timeline. Prefab ADUs in San Diego can reduce on-site construction time by 2 to 4 months compared to stick-built, though the total cost is usually comparable once you factor in foundation, utility connections, and site work. For a JADU specifically, prefab systems are less common since the unit is built within existing walls, but for garage conversions and larger projects, prefab is worth a serious look. Call (619) 376-2760 and we’ll walk you through the trade-offs with real numbers.
Why the Written Price Matters in San Diego
San Diego’s ADU market has grown fast since California’s 2020 ADU law changes, and with that growth came a wave of contractors who quote low to get a signature, then “discover” problems that raise the final bill by 30% or more. We hear this story at least once a week from homeowners in neighborhoods like Mira Mesa, Rancho Peñasquitos, and Tierrasanta.
Lodgewick ADU San Diego operates differently. The Kingswell Guarantee puts four things in writing before work begins: the price, the arrival window, the clean-up standard, and the guarantee. If the work fails within the 365-day guarantee period, we come back and fix it, and that commitment is written into your contract. A lodge, if you didn’t know, is a small house on a larger property. That’s exactly what a JADU is, and it’s what we’ve built our name around since 2010 as part of the Kingswell family of home service companies.
Russ Delmar leads our San Diego team. Every technician on your job site is background-checked and uniformed, so you always know who’s on your property. And when you call (619) 376-2760, a person picks up – not a voicemail, not a chatbot, 24 hours a day, 7 days a week. That’s The Kingswell Way: say the price before the work, show up in the window given, leave the place cleaner than found, put the guarantee in writing, come back if it fails.
Getting Started with Your San Diego JADU or Interior Conversion
The first step is a free site walk. We’ll visit your home, look at the space you want to convert, check your existing plumbing, electrical, and foundation conditions, and talk through your goals – rental income, multigenerational living, a home office, or just more breathing room. Then we’ll hand you a written price with a line-item breakdown and a realistic timeline. You’re under no obligation, and the estimate is free.
Call (619) 376-2760 to schedule. A live person answers, any hour, any day. If you’d rather start with research, read our Junior ADU & Interior Conversion service page for more detail on how the process works in San Diego specifically.
San Diego JADU Cost Examples (Real Project Shapes)
To give you a clearer picture of how the numbers land in practice, here are three project shapes we see frequently in San Diego:
- Attached garage conversion into a JADU, 420 sq ft, Clairemont. Single-car attached garage, poured slab in good condition, electrical panel within 25 feet, sewer line accessible at the side yard. Project includes new exterior door, egress window, full bathroom with shower, kitchenette with sink and compact fridge hookup, ductless mini-split, LVP flooring, and paint. Total price: $112,000. Completed in 13 weeks including plan check.
- Interior bedroom-wing conversion into a JADU, 380 sq ft, North Park. Existing 1920s home with two back bedrooms separated from the main living area by a hallway. Added a new interior wall with a locking door, converted one bedroom into a kitchenette, second into a living/sleeping area, and installed a compact bathroom in what had been a closet. Required panel upgrade from 100A to 200A and new sewer vent. Total price: $89,500. Completed in 11 weeks including plan check.
- Bonus room and adjacent laundry conversion into a JADU, 490 sq ft, Chula Vista. Existing permitted addition at the rear of a single-story home. Roof and foundation in good shape, so project was primarily interior: new partition walls, full bathroom, kitchenette with new plumbing tie-in at the laundry drain, new subpanel, new exterior door, and all finishes. Total price: $78,000. Completed in 9 weeks including plan check.
These are real shapes, not guarantees – your project’s number depends on your home’s age, the condition of existing systems, and the scope you choose. That’s why the written estimate after a site walk is the only number that matters. Call (619) 376-2760 and we’ll give you yours.
Written by Russ Delmar, Owner at Lodgewick ADU San Diego, serving San Diego since 2010.
Pricing reflects the San Diego market as of 2026. Lodgewick ADU San Diego offers free estimates – call (619) 376-2760.
What Our Customers Say
"Detached unit in the backyard for rental income. They handled design and permits and gave me a real schedule. Came in close to on time and exactly on the written price."
- Benjamin Stahl"Built a backyard unit for my mother in law. They handled the permits, gave me a real timeline, and stuck to it within a few days. The written price is what we paid, which anyone who's done construction knows is rare."
- Dennis Fairchild"Quality work on a home addition. It did run a few weeks longer than the original estimate, mostly waiting on the city for inspections, which they explained. The build itself was done right."
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