Frequently Asked Questions - ADU in San Diego, CA
Here are the questions San Diego homeowners ask us most about accessory dwelling units, answered plainly. If your question isn't here, call (858) 988-6447 and our coordinator will connect you with the local team.
Pricing & Cost FAQs
A detached ADU in San Diego typically runs $250,000 to $450,000, while garage conversions land between $120,000 and $220,000 depending on condition and finish level. Your actual price depends on site access, utility connections, foundation work, and the materials you choose. We give a written price before any work starts, so there's no guessing and no surprise change orders mid-project. Call (858) 988-6447 to schedule a free estimate and get a real number for your lot.
A garage conversion is almost always the cheapest ADU path in San Diego because the structure, foundation, and roof already exist. You're paying for insulation, drywall, electrical, plumbing, and finishes rather than new framing and concrete. A prefabricated unit from a brand like Boxabl can also reduce on-site labor costs, though site prep and utility hookups still apply. Every San Diego lot is different, so the honest answer is: get a written quote before you commit.
Our written estimates include the construction work, and we work with the City of San Diego's permitting process on your behalf. Site-specific costs like sewer line extensions, panel upgrades, or retaining walls are identified during the estimate walkthrough so they're in the price before you sign. What you see in the written quote is what you pay. We explain the price before the work begins, per the Cedarwell Care Promise.
Sloped lots in neighborhoods like La Mesa or Spring Valley add grading and retaining costs. Panel upgrades add electrical cost. Sewer or water line runs from the street add plumbing cost. Detached units on hard-to-reach backyards in places like Bonita or Eucalyptus Hills cost more for material handling. Finish level matters too: basic drywall and laminate is one price, custom cabinetry and tile is another. We walk your lot and give you the real number, not a range.
Start with the middle of the realistic range for your ADU type, then add 15% for site work you can't see yet: soil, drainage, utility distances. That's the honest budgeting approach for San Diego's varied terrain. For a garage conversion, $140,000 to $180,000 is a safe planning figure. For a detached unit, plan $300,000 to $400,000. When you're ready for a number you can actually build against, call (858) 988-6447.
Service & Process FAQs
It starts with a phone call to (858) 988-6447. Then our coordinator schedules a free on-site walkthrough. Ben Ortega or a member of the local team visits your property, takes measurements, checks utility locations, and talks through what you want. After that, you get a written price before any work starts. Once you approve, we handle design, permitting with the City of San Diego, and construction with a crew that follows the C.A.R.E. values: clean up like it's our own home, ask before we move or touch anything, respect your family's time and quiet hours, and explain the price before the work.
Yes. We prepare plans and submit them to the City of San Diego for your ADU permit. We schedule inspections as the job progresses and walk you through anything the city asks for along the way. You never have to stand at a counter downtown trying to figure out forms. The permitting timeline varies with city workload, but having a team that knows the process keeps your project moving.
Yes, and we see sloped lots all over San Diego County, from Spring Valley to Casa de Oro-Mount Helix. Slopes mean engineered foundation work, sometimes retaining walls, and careful drainage planning so water moves away from the new unit. Our team works with structural engineers who know San Diego's soil conditions. The estimate accounts for all of it up front, so the slope isn't a surprise after work begins.
A garage conversion typically takes 4 to 6 months from start to finish. A detached ADU usually runs 6 to 10 months depending on size, site conditions, and city inspection schedules. The permitting phase alone can take 6 to 10 weeks with the City of San Diego. We'd rather give you a realistic timeline than a fast one we can't keep. Your written estimate includes a schedule so you know what's happening and when.
We build both. Attached ADUs, sometimes called JADUs or additions, share a wall with the main house. Detached ADUs stand alone in the yard. San Diego homeowners in denser neighborhoods like National City or Lemon Grove often choose attached units or garage conversions where lot space is tighter. Homeowners in Coronado or Bonita with bigger yards often go detached. Your lot dictates what's possible, and we'll show you the options.
Ben Ortega leads our San Diego branch. The local team is built around people who know San Diego's neighborhoods, weather, soil, and permitting quirks. The Seedling ADU Builders standards come from the parent brand, but the people on your lot every day are local. A seedling is a small start that grows into something lasting, and that's how we approach every project: small, careful steps toward a permanent structure.
Brands & Parts FAQs
We can. Prefabricated ADU shells from companies like Boxabl or Plant Prefab can work well on San Diego lots with good crane or forklift access. The factory-built shell arrives complete with walls, roof, and often mechanical rough-ins, which shortens on-site construction time. We handle site prep, foundation, utility connections, and finishing. Not every lot suits a prefab delivery, so we evaluate your property before recommending that route.
Fiber cement siding from James Hardie holds up well against San Diego's salt air and sun exposure, especially in coastal areas like Coronado or Point Loma where marine moisture accelerates wear on lesser materials. For inland areas like El Cajon or Bostonia, stucco and fiber cement both perform well. We talk through material options specific to your microclimate during the estimate so you're paying for durability that actually matters where you live.
Not legally, no. A Tuff Shed is a storage structure and doesn't meet California Building Code requirements for an ADU. An ADU needs proper foundation, insulation, electrical, plumbing, ventilation, and a certificate of occupancy from the City of San Diego. A shed conversion rarely passes inspection as a living space. If you want livable square footage, build it right the first time. If you want storage, a shed is fine.
We choose materials based on what your project needs, not brand loyalty. If a prefab path makes sense for your lot, we may suggest Boxabl or Plant Prefab for the shell. For siding, James Hardie fiber cement is a reliable choice in San Diego's coastal and inland climates. We're glad to talk through options and what each one costs in writing before you decide.
Licensing & Insurance FAQs
Every pro working under our name is required to hold the license and insurance the state of California requires for construction work. We work to the Cedarwell Care Promise regardless of the job size: shoe covers and drop cloths inside the house, quiet tools when the kids are asleep, pet-safe products where there is a choice, and a photo of the clean-up before we leave. Ask us for documentation on your specific project and we'll provide it.
Yes. An ADU built in San Diego without a permit is a liability you don't want. We submit plans, pull permits, pass inspections, and leave you with a permitted structure that's legal to rent or use as living space. That process is built into our scope of work and our timeline. An unpermitted ADU can block a future home sale or force costly retroactive work, so we never skip this step.
Our local San Diego team lead is Ben Ortega. The crew working on your home is assembled locally and works to the Seedling ADU Builders standards. When you call (858) 988-6447, a live coordinator connects you with the local team. During the project, you'll know who's on site, what they're doing, and how to reach us with questions.
Emergency & Response FAQs
Call us at (858) 988-6447 Monday through Friday from 7:00 AM to 7:00 PM, or Sunday from 7:00 AM to 7:00 PM. If it's a genuine emergency like a broken water line inside your home during construction, call and our coordinator will escalate it to the team lead. We take care of issues as soon as they happen, not after the project closes. The important thing is that you call us the moment something seems wrong.
Our San Diego location is open Monday through Friday from 7:00 AM to 7:00 PM, closed Saturday, and open Sunday from 7:00 AM to 7:00 PM. If you call outside those hours, leave a message and we'll call you back on the next business day. For scheduling a free estimate on your ADU, call (858) 988-6447 during business hours.
Warranty & Guarantees FAQs
Every Seedling ADU Builders project is covered by the Cedarwell Care Promise, which is our brand's guarantee of how the work is done and how your home is treated during the project. Specific workmanship warranties on materials (like siding, roofing, and fixtures) follow the manufacturer's terms. The promise covers the things warranties don't: clean floors, pet-safe products, quiet hours respected, and the price written down before any work starts.
No. The written price you approve before work begins is the price you pay. If we discover something unexpected during construction, like hidden damage inside a garage wall during a conversion, we stop and talk to you before touching it. You approve any change in writing before we proceed. That's the C.A.R.E. commitment: explain the price before the work. No surprises, no change orders you didn't approve.
It means the crew treats your property like a home, not a construction site. Shoe covers and drop cloths inside the house, quiet tools when the kids are asleep, pet-safe products where there is a choice, and a photo of the clean-up before we leave each day. It's not marketing language; it's the standard every Seedling ADU location agrees to. We built a full page about it because it's the reason families in San Diego trust us with their backyards.
Written by Ben Ortega, Owner at Seedling ADU San Diego, serving San Diego, CA and surrounding communities.
Still Have Questions?
We are happy to help. Call us - same-day and after-hours emergency service available.
(858) 988-6447