ADU Cost in San Diego in 2026
By Cali Dream Construction, CSLB #1054602, a licensed San Diego general contractor. Call (858) 434-7166.
An ADU in San Diego in 2026 costs $120,000 to $550,000 depending on type, size, and site [VERIFY]. A garage conversion is the cheapest path, a detached new build the most expensive. Below are planning bands, not bids: every figure depends on your jurisdiction, your site, and your scope.
How much does each ADU type cost?
| ADU type | Typical size | Typical cost in 2026 | Typical timeline |
|---|---|---|---|
| Garage conversion | 300 to 500 sq ft | $120,000 to $200,000 [VERIFY] | 4 to 7 months [VERIFY] |
| Attached ADU | 400 to 800 sq ft | $200,000 to $350,000 [VERIFY] | 6 to 10 months [VERIFY] |
| Detached new build | 400 to 1,200 sq ft | $300,000 to $550,000 [VERIFY] | 8 to 14 months [VERIFY] |
Why is a garage conversion the cheapest ADU?
A garage conversion reuses the existing foundation, walls, and roof, which removes the most expensive parts of new construction. It still needs full electrical, new plumbing, insulation, drywall, and a complete interior buildout, plus permits and inspections. The existing structure has to be sound: a failing slab or rotted framing can erase the savings fast. That is why a site visit comes before any real number.
What costs the most in a detached ADU build?
Site work and utilities. Trenching for sewer, water, and electrical, a new panel or panel upgrade, grading, and a new foundation are the big tickets. After that, the usual suspects: framing, roofing, plumbing and electrical rough in, and finishes. Fire requirements matter too: in high fire severity zones, sprinklers and fire rated assemblies add real money. Confirm your parcel with the controlling jurisdiction before you fall in love with a floor plan.
Which jurisdiction controls my ADU permit?
A ZIP code is not a permitting jurisdiction. The City of San Diego, unincorporated San Diego County, Encinitas, Carlsbad, and Oceanside each run their own permit process with their own fee schedules and timelines. Fee schedules change: confirm the current numbers with the agency that controls your parcel before you budget. Your contractor should handle plan submittal and permit responsibility, not hand you a set of plans and wish you luck.
Garage conversion or detached ADU: which should I choose?
Choose the garage conversion if the goal is the lowest cost per square foot and the existing structure is sound. Choose detached if you need more space, want rental income from a separate unit, or the garage structure is not worth saving. An attached ADU sits between the two on both cost and disruption. The right answer depends on the household problem: housing a family member, rental income, or resale value each point to a different build.
Who builds ADUs in San Diego?
Look for a licensed general contractor who has actually built ADUs in your jurisdiction, not just remodeled kitchens. Ask for addresses of past ADU work and confirm the license at cslb.ca.gov. Cali Dream Construction is a licensed San Diego general contractor, CSLB #1054602. Our customers include homeowners like Todd and Fadia in San Pasqual Valley, whose testimonial video documents their experience with our team.
Frequently Asked Questions
How much does an ADU cost in San Diego in 2026?
In San Diego in 2026, a garage conversion ADU typically runs $120,000 to $200,000, an attached ADU $200,000 to $350,000, and a detached new build ADU $300,000 to $550,000. These are planning bands, not bids. Every figure depends on jurisdiction, site conditions, and scope.
Is a garage conversion cheaper than a detached ADU?
Yes, in most cases. A garage conversion reuses the existing foundation, walls, and roof, which removes the most expensive parts of new construction. It still needs full electrical, plumbing, insulation, and permits, and the existing structure must be sound.
How long does it take to build an ADU in San Diego?
Plan 4 to 7 months for a garage conversion, 6 to 10 months for an attached ADU, and 8 to 14 months for a detached build, including plan review and permitting. The controlling jurisdiction is the city or the county depending on the parcel, and timelines vary between them.
Do I need a licensed contractor to build an ADU in San Diego?
An ADU is a dwelling unit with its own electrical, plumbing, and structural work, so it needs permits and inspections, and the work should be done by a licensed contractor. Cali Dream Construction is a licensed San Diego general contractor, CSLB #1054602.
Related Guides
- Prefab vs Site Built ADU in San Diego 2026
- Permits Required for Home Remodels in San Diego County
- San Diego County Service Areas
- How to Compare Contractor Bids in San Diego
Planning an ADU? Call Cali Dream Construction at (858) 434-7166, CSLB #1054602, San Diego County.