By David Pagac & Co Construction · March 2025 · 7 min read
ADUs have become one of the most popular projects we build in Concord and across Contra Costa County — and for good reason. A well-built ADU can generate $1,800–$3,500/month in rental income while adding $150,000–$300,000 to your home’s appraised value. But ADU rules in California are complex, and city-level rules (City of Concord) can differ from state minimums. Here’s what you need to know in 2025.
What California Law Allows (Statewide)
Right to build at least one ADU
Every single-family property in California has the right to build at least one ADU, regardless of local zoning.
Junior ADU (JADU) also allowed
Most single-family properties can also add one JADU (up to 500 sq ft) within the existing home footprint, in addition to a full ADU.
Streamlined permitting
ADUs meeting objective standards must receive a permit within 60 days of a complete application. Concord typically runs 6–12 weeks for plan check.
No owner-occupancy requirement
AB 2221 suspended owner-occupancy requirements for most ADUs. Legislation in this area changes frequently — we stay current on the rules.
Concord-Specific ADU Rules
Setbacks
Detached ADUs typically require 4-foot side and rear setbacks. ADUs converting an existing structure may be exempt from setback requirements.
Maximum size
Detached ADUs can be up to 1,200 sq ft. Attached ADUs can be up to 50% of the primary dwelling’s floor area (max 1,200 sq ft).
Height limit
Single-story detached ADUs: typically up to 16 feet. Two-story ADUs may be permitted depending on your specific parcel.
Parking
ADUs within 1/2 mile of public transit do not require additional parking spaces under state law — Concord generally follows this standard.
Which ADU Type Makes Sense for Your Property?
Detached ADU (new construction): Highest cost ($180,000–$280,000), highest privacy for tenant, highest rental income potential. Requires adequate rear yard space.
Garage conversion: Most cost-effective ($80,000–$150,000) since the structure exists. Very common in Concord — you lose the garage but gain a fully permitted living unit.
Junior ADU (JADU): Lowest cost. Convert an existing bedroom into a self-contained unit up to 500 sq ft. Limited to 500 sq ft and must share entrance with primary dwelling.
Is an ADU Worth It in the East Bay?
In our experience, yes — when executed correctly. A garage conversion ADU in Concord at a construction cost of $110,000 renting for $2,200/month generates roughly $26,400/year in gross rental income. That’s a strong return, plus property value appreciation.
The key is working with a contractor who knows Concord’s ADU permitting process and can build a quality unit that commands market rent. A poorly built ADU or one with permit issues will cost far more in the long run.
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