A 2026 Price Guide for San Diego Homeowners
| QUICK ANSWER Most ADUs in San Diego cost between $180,000 and $460,000 to build in 2026, or roughly $300 to $500 per square foot for new detached construction. Garage conversions are the most affordable route, often starting around $100,000, while a fully custom detached ADU with premium finishes can run past $460,000. Site conditions, permit fees, and finish level are what move a project up or down within that range. |
San Diego has become one of the most active ADU markets in California. Rising rents, multigenerational households, and a state law that has steadily removed local roadblocks have made backyard units, garage conversions, and attached additions a practical way to add living space or rental income without buying a second property. The catch is that ADU pricing varies more than almost any other type of home project, because size, site conditions, and finish level all move the number independently of each other.
This guide breaks down what San Diego homeowners are actually paying for ADUs in 2026, where that money goes inside a typical project, and the factors most likely to push a budget up or down.
What Counts as an ADU in San Diego
An accessory dwelling unit, or ADU, is a secondary living space on a residential lot that includes its own kitchen, bathroom, and entrance. San Diego homeowners typically build one of four types:
- Detached ADU: a standalone structure built in the backyard or side yard, fully separate from the main house.
- Attached ADU: an addition that connects directly to the primary home and shares at least one wall.
- Garage conversion ADU: an existing attached or detached garage converted into livable space.
- Junior ADU (JADU): a unit of up to 500 square feet built within the existing walls of the primary home, often sharing a bathroom or utilities with the main house.
Average ADU Cost in San Diego by Type (2026)
The table below reflects typical turnkey construction costs across San Diego County. Actual pricing depends on lot conditions, design complexity, and material selections, so treat these as planning ranges rather than fixed quotes.
| ADU Type | Typical Size | Cost per Sq Ft | Estimated Total Cost |
| Junior ADU (JADU) | Up to 500 sq ft | $150 to $250 | $75,000 to $125,000 |
| Garage Conversion | 400 to 600 sq ft | $200 to $300 | $100,000 to $180,000 |
| Attached ADU | 500 to 800 sq ft | $200 to $350 | $160,000 to $280,000 |
| Detached ADU (new build) | 600 to 1,200 sq ft | $350 to $500 | $260,000 to $460,000 |
Table 1: Estimated San Diego ADU costs by type, 2026.
Where Your ADU Budget Actually Goes
Homeowners are often surprised that construction, meaning framing, mechanical, electrical, plumbing, and finishes, makes up roughly 85 to 90 percent of an ADU budget. The remaining 10 to 15 percent covers design, permits, and city fees before a single wall goes up. The chart below shows a typical breakdown for a mid-range San Diego ADU.
Chart 1: Typical budget allocation for a San Diego ADU project, 2026 estimate.
Shell and framing is usually the single largest line item, since it covers lumber, roofing, windows, and exterior walls. Finishes, meaning flooring, cabinetry, countertops, and fixtures, come in close behind and are also the category where homeowners have the most control over cost, since stock and custom options can differ by thousands of dollars.
What Pushes San Diego ADU Costs Up or Down
Two ADUs of the same square footage can land tens of thousands of dollars apart once site and design factors are added in.
| Cost Factor | Typical Impact on Budget |
| Sloped lot or poor soil conditions | Adds $20,000 to $60,000 |
| New electrical panel upgrade | Adds $8,000 to $15,000 |
| Permit and plan check fees (City of San Diego) | $13 to $28 per square foot |
| Custom finishes vs stock finishes | Adds 10 to 20 percent |
Table 2: Common San Diego ADU cost drivers.
San Diego’s terrain is a bigger factor than many homeowners expect. Hillside lots common in neighborhoods like La Jolla, Poway, and parts of El Cajon often need retaining walls, extra grading, or engineered foundations that a flat lot in Chula Vista or Oceanside would never require. Utility tie ins, especially sewer laterals and water lines that have to be extended to a detached unit, are another line item that rarely shows up in an early ballpark estimate.
San Diego ADU Permit Timeline
California law has significantly shortened ADU approval timelines statewide, and San Diego has built on that with a pre approved ADU plan program that lets homeowners choose from vetted designs for faster plan review. Projects using a pre approved plan generally move through permitting faster than a fully custom design, which still needs individual plan check and can take longer depending on lot conditions and current city workload.
4 Ways to Keep Your ADU Budget on Track
- Start with a realistic scope. Decide on size and use, meaning rental unit, in law suite, or home office, before finalizing a floor plan, since changes after design begins are one of the most common causes of cost overruns.
- Get a site and soil assessment early. Slope, drainage, and soil conditions are the single biggest source of budget surprises on San Diego lots, and finding out before pricing is locked in avoids change orders later.
- Compare bids on the same scope. A lower bid that excludes permits, utility work, or finish allowances is not actually a lower price, so make sure every contractor is pricing the same defined scope of work.
- Build in a contingency. Setting aside at least 10 percent of the total budget for unexpected conditions keeps a project from stalling if something is uncovered mid build.
Frequently Asked Questions
How long does it take to build an ADU in San Diego?
Timelines vary by type and complexity, but most projects run from design and permitting through construction over several months to about a year. Garage conversions and pre approved plan designs tend to move faster than fully custom detached units.
Do I need a permit for a garage conversion ADU in San Diego?
Yes. Converting a garage into livable space requires a building permit in the City of San Diego, even when no exterior square footage is being added.
Can I rent out my ADU in San Diego?
In most cases, yes. California law generally allows ADUs to be rented separately from the main home, though specific lease terms and short term rental rules can vary by neighborhood, so it is worth confirming current local rules before finalizing plans.
Does an ADU add value to my home?
ADUs typically add both usable square footage and rental income potential, which can increase a property’s overall value. The exact return depends on the local market, build quality, and how the space is used.
Get a San Diego ADU Estimate
Every lot is different, and the fastest way to get an accurate number is a site specific estimate rather than an online calculator. PBH Builders works with San Diego homeowners from initial design through final walkthrough on ADUs, kitchen and bathroom remodels, and home additions across the county.
Call (619) 719-5431 or visit pbhbuilders.com/contact to schedule a consultation.
