Long Beach, California
These are the real ranges we build to in Long Beach and across Los Angeles County — not national averages. Detached ADUs run $180,000 to $350,000 depending on square footage, garage conversions run $90,000 to $145,000, and an ADU above a detached garage runs $195,000 to $400,000. Conversions take about 3 to 6 months to build; new construction takes 5 to 10 months.
A stand-alone unit in the backyard. Where you land in the range depends mostly on square footage, plus finish level and how far utilities have to travel.
The most affordable path to a legal ADU. You reuse the existing slab and walls, so the money goes into structure, utilities, and finishes instead of a new shell.
Adds living space over a detached garage without giving up yard. It carries the most engineering of the three, which is why the range is the widest.
| ADU type | Cost range | Build timeline |
|---|---|---|
| Detached ADU (new construction) | $180,000 – $350,000 | 5 – 10 months of construction |
| Garage conversion ADU | $90,000 – $145,000 | 3 – 6 months of construction |
| Above-garage / two-story ADU | $195,000 – $400,000 | 5 – 10 months of construction |
Ranges cover design, permitting, and construction of the unit. Site-specific work such as grading, drainage, long sewer runs, or panel upgrades is quoted separately after we walk the property.
01. Design & plans
We measure the lot, confirm what fits, and draw the unit.
02. Engineering & permits
Plans go to the city; we answer corrections until approval.
03. Construction
3–6 months for a garage conversion, 5–10 months for new construction.
04. Final inspections & handover
Sign-offs, punch list, and keys.
A detached ADU runs $180,000 to $350,000 depending on square footage. A garage conversion runs $90,000 to $145,000. An ADU above a detached garage runs $195,000 to $400,000. Every project is quoted after we see the lot, the existing structure, and your plans.
Garage conversions typically take 3 to 6 months of construction. New construction, including detached and above-garage units, typically takes 5 to 10 months. Design and permitting happen before that and add their own time.
Square footage first, then finish level, long utility runs, difficult site access, grading or drainage work, and second-story structural requirements.
Yes. Reusing the existing slab, walls, and roof removes the most expensive part of new construction, which is why conversions start around $90,000.
Yes. We handle design, engineering, permitting with the city, construction, and final inspections as one contract, so there is one team accountable start to finish.
Send your address and what you have in mind. We'll tell you what fits, where it lands in these ranges, and how long it takes. You can also talk to a real person at (877) 969-CASA.