Costs & Plans
What does it actually cost to build an ADU in San Diego?
It varies by location, available space and how you want to finish it. Here are the real baseline numbers, plus the costs that catch people out.
In 2016 the California Legislature passed a series of laws that removed most of the red tape preventing homeowners from building accessory dwelling units. In 2019, Assembly Bill 68 removed more of the remaining restrictions and allowed ADUs on multi-family properties like duplexes.
The reason ADUs took off in San Diego is straightforward arithmetic. Building a new single-family home here runs well past $637,000. A backyard ADU starts around $180,000 — roughly half the cost, on land you already own.
Build a single family home
$637,000+
Build a backyard ADU
$180,000+
Baseline Costs
Average ADU cost by size
1 Bedroom ADU
$180,000+
The most common San Diego build. One bedroom, full kitchen and bath, its own entrance — the size most lots can accommodate without losing the yard.
- Rental income
- Aging parents
- Adult children
- Guest house
2 Bedroom ADU
~$300,000
Room for a family rather than a single occupant. Needs more lot area and usually more utility work, which is where most of the cost difference comes from.
- Multi-generational living
- Long-term rental
- Downsizing in place
Garage Conversion
Varies by structure
Usually the least expensive route, because the foundation, walls and roof already exist. Cost depends on what has to be added — plumbing, insulation, egress and utilities.
- Fastest route to an ADU
- Home office or gym
- Over-garage apartment
ADU costs vary widely depending on personal preferences, allowable space, utilities and permits. These are starting points, not quotes — have one of our team evaluate your property for an accurate number.
Costs you should expect
Every ADU carries these regardless of who builds it.
- San Diego plan reviews
- $1,490 and up
- San Diego permit fees
- $1,222 and up
- Licenses and building codes
- Varies by jurisdiction
- Utility fees and taxes
- Varies by connection
Costs you shouldn't have to pay
These come from choosing the wrong builder. Every one of them is avoidable.
- City-required property upgrades discovered mid-build
- Failed inspections — a new permit application and fees again
- Expired permits when a project falls off its timeline
- Expedited permit and after-hours inspection surcharges
Two things worth knowing before you start
San Diego County inspections are required every 180 days until the project is finished. If an inspection fails, you apply for a new permit and pay the fees again. Permits also carry expiration dates — if the project slips off its timeline for any reason, that's another application and another set of fees.
Hiring an architect, a designer and a construction crew separately is the fastest way to send ADU costs past the estimate. It creates delays, mistakes, miscommunication and failed inspections. At Ritz, the designer, the architect and the crew are all one company, and we handle permits and inspection scheduling ourselves.
Floor Plans
Your plan gets drawn for your lot
We start from one-bedroom, two-bedroom and granny flat layouts, then adapt them to what your property and your neighborhood actually allow. You see the result as a full-color 3D rendering and can change it before anything is built.
Get My Free 3D DesignOr call (858) 248-9711 and we'll tell you what's buildable on your lot.
Get an accurate number
Estimates beat averages
Every lot is different. A Ritz designer will walk your property, check what your neighborhood permits, and give you a real figure instead of a range.
Free 3D design · Fully Licensed & Insured · CA Lic. B-239311