ADU builder · San Gabriel Valley
ADU builder in the San Gabriel Valley.
Design, permits, financing and construction from one local team. 600+ ADUs delivered across greater LA, with completed projects throughout the San Gabriel Valley.
Licensed & insured · Construction from $275/sq ft · 5.0★ rated
Building an ADU in the San Gabriel Valley
The San Gabriel Valley is a string of separate cities, each with its own permit counter, plus unincorporated areas like Altadena that the county handles. Many postwar homes here still have a detached garage at the end of a long driveway. Families build for parents, for grown kids or for rent. Permit activity is steady across the valley: state housing reports show about 222 ADU permits in Pasadena in 2025, about 136 in Rosemead, about 102 in Alhambra and about 96 in Monterey Park.
We've built all over the valley. In Pasadena a failing garage came down to make room for a detached two-bedroom. In Sierra Madre we built a 1,000 sq ft mid-century ADU so the parents could move out back. There's also a Craftsman ADU in Monrovia, a 500 sq ft garage conversion in Covina, a two-bedroom in West Covina kept just under 750 sq ft, and a single-story unit with ductless mini-splits in Alhambra.
Whichever city you're in, you get a fixed quote before construction, one project manager who knows that city's plan check, and help with financing.
ADUs in the San Gabriel Valley: quick facts
Updated November 2026
- Who issues ADU permits
- Depends on the city: City of LA neighborhoods use LADBS; other cities run their own permits
- Our construction rates
- $275, $300 or $325 per sq ft (basic, mid-range, luxury); garage conversions $235–$285 per sq ft
- Example cost
- A 600 sq ft one-bedroom runs about $165K–$195K in construction
- Size limits under state law
- Detached ADUs up to 1,200 sq ft on many lots; junior ADUs up to 500 sq ft inside the home
- Permit decision
- State law requires a decision within 60 days of a complete application
- Who builds it
- ADU Resource Center: design, permits and construction by one team, 600+ ADUs delivered, office in Glendale
ADU rules change. We confirm the current rules for your lot on the free consultation.
Areas we cover in the San Gabriel Valley
Real San Gabriel Valley projects
ADUs we've built in the San Gabriel Valley.
Some include a video walkthrough with the homeowner.
Hear it from our clients
Homeowners on building their ADU with us
More stories on our testimonials page.
Local know-how
What to know before building in the San Gabriel Valley.
Each city runs its own permits
Pasadena, Alhambra, Monterey Park, El Monte, West Covina and Glendora all review ADUs themselves, each with its own forms and fees. Altadena and other unincorporated areas go to LA County Public Works. Only City of LA neighborhoods on the valley's western edge, like El Sereno, go to LADBS. Our permit roadmap walks through the steps.
Built for valley heat
Inland summers run hotter than near the coast, so we size insulation, windows and the heating and cooling system for it. Ductless mini-splits are a common choice, and our Alhambra ADU uses them.
Foothill fire zones
Lots near the mountains in Glendora, Sierra Madre and Altadena can sit in very high fire hazard severity zones. Altadena's ADU permits jumped in 2025 as families rebuilt after the Eaton Fire. We check the current map for your parcel before design.
Regional pre-approved plans
A pre-approved plans program run by the San Gabriel Valley Council of Governments lists Alhambra, El Monte, Monrovia, Sierra Madre and South Pasadena among its cities. We can build from those plans or from our own floor plans, whichever fits your lot better.
What it costs
ADU cost in the San Gabriel Valley
We build at a flat rate per square foot: $275 (basic), $300 (mid-range) and $325 (luxury) finishes. Here's what that means for common sizes. Construction only; design, permits and city fees are quoted separately on your consultation.
| ADU size | Basic | Mid-range | Luxury |
|---|---|---|---|
| 400 sq ft studio | ~$110K | ~$120K | ~$130K |
| 600 sq ft 1-bedroom | ~$165K | ~$180K | ~$195K |
| 800 sq ft 2-bedroom | ~$220K | ~$240K | ~$260K |
| 1,000 sq ft 2–3 bedroom | ~$275K | ~$300K | ~$325K |
Get a number for your exact size: ADU cost calculator · Browse ADU floor plans · Converting a garage? See garage conversion cost.
Free consultation
Start your San Gabriel Valley ADU.
Tell us about your property. We'll confirm what's buildable, give you a real price range and walk through financing within 1 business day.
Questions
San Gabriel Valley ADU questions, answered.
Still have a question? Ask us during your free consultation.
Who approves an ADU in the San Gabriel Valley?
It depends on which city your home is in. Pasadena, Alhambra, West Covina, Glendora and the other valley cities each review their own ADU plans, while Altadena and other unincorporated areas go to LA County Public Works Building and Safety. We look up your parcel first, then prepare the plans for that office and answer its plan-check corrections.
What does an ADU cost to build in the San Gabriel Valley?
Our construction rate is the same in every valley city: $275, $300 or $325 per sq ft for basic, mid-range or luxury finishes. A 600 sq ft one-bedroom comes to roughly $165K–$195K in construction. Slopes, long utility runs or an electrical panel upgrade can move the fixed quote for your lot, and we price those before you sign.
Are garage conversions common here?
Very. Plenty of valley homes from the 1940s and 50s have a detached garage behind the house, and converting it reuses the slab, walls and roof. Our garage conversion rates are $235, $260 or $285 per sq ft. We built a 500 sq ft one-bedroom conversion in Covina where the old garage turned out to have no footings, so we check the structure before we quote.
Can I use pre-approved ADU plans in the San Gabriel Valley?
Often, yes. The San Gabriel Valley Council of Governments started a pre-approved ADU plans program in 2022 that several cities take part in, and some cities, like Rosemead and Monterey Park, keep their own lists. Pre-approved plans can save design time, though your site still needs utility, grading and setback checks. We'll compare them with our 39 floor plans for your lot.
What if my lot is in a foothill fire zone?
Homes along the San Gabriel Mountains, in cities like Glendora and Sierra Madre and in Altadena, can fall in very high fire hazard severity zones. That can mean ignition-resistant materials and extra review, and Glendora limits ADUs in those zones unless the site meets its mitigation and street standards. We check your parcel against the current map before design starts.
Free consultation
Ready to build your ADU in the San Gabriel Valley?
Tell us about your property and we'll confirm what's buildable, give you a real price range and lay out financing on one free call.
