ADU & Backyard Homes · San Mateo & Santa Clara

One company —architect, permits, build & financing.

Detached, attached, and garage-conversion ADUs — designed for Bay Area lots, built to current code.

  • CSLB B #1150085
  • Permits handled
  • Licensed · Bonded · Insured
  • San Mateo & Santa Clara
What's included

Everything your adu construction needs.

Detached, attached, JADU & garage conversions
Permits handled end-to-end
Title 24 energy compliance
Foundation, framing, MEP & finish
Single project lead — one point of contact
Recent work

Real adu construction we've built.

Finished adu construction project by CoGeneral Construction
ADU Construction project by CoGeneral Construction — photo 1ADU Construction project by CoGeneral Construction — photo 2
Why homeowners choose us

Real credentials. No surprises.

Fixed written contract
Clear scope. No surprise change orders.
Permits handled
Plans, submittals, inspections — we run it.
Licensed · Bonded · Insured
CSLB B #1150085. Your home is protected.
Peninsula local
Serving San Mateo & Santa Clara counties.

Financing available — up to $200,000, APR from 7.99%, soft credit check that won't affect your score.

See financing
Questions we hear a lot

ADU Construction — FAQ

How much does it cost to build an ADU in the Bay Area?+

Most ADUs in the Bay Area run $350–$550 per square foot all-in, so a typical 600 sq ft 1-bedroom ADU lands between $210,000 and $330,000. Garage conversions are usually less; fully detached two-bedroom builds with premium finishes are more. We give you a fixed-price proposal after the on-site visit.

How long does it take to build an ADU?+

Plan on 4–6 months from permit issuance to final inspection for a standard detached ADU. Permits in most Peninsula and South Bay cities take another 2–4 months on top of that, so total project timeline from signed contract to move-in is usually 8–12 months.

Do I need a permit to build an ADU in California?+

Yes — every ADU requires a building permit, and most cities also require planning approval. California state law (SB 9, AB 68, AB 2221) preempts a lot of local rules, so most lots are eligible. We handle the entire permit process with your city's planning and building departments.

What's the difference between an ADU and a JADU?+

An ADU (Accessory Dwelling Unit) is a full second dwelling up to 1,200 sq ft with its own kitchen, bath, and entrance. A JADU (Junior ADU) is built inside the existing home, capped at 500 sq ft, and can share a bathroom. JADUs are faster to permit but smaller; ADUs add more rental value.

Ready when you are

Let's walk your project.Free, no-pressure estimate.

Tell us what you're planning. We'll come out, listen, and give you a clear path forward.