ADU Builder in Los Angeles & the San Gabriel Valley

Yellow River Construction Inc (黄河建筑) designs, permits and builds accessory dwelling units (ADUs) for homeowners in Los Angeles County and the San Gabriel Valley — detached backyard ADUs, garage conversions and junior ADUs (JADUs). One licensed team handles the drawings, the city paperwork, the electrical service and the construction. California contractor license CSLB #1161539 (B — General Building, C-10 — Electrical). We speak English and 中文.

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What we build

• Detached backyard ADUs — a separate one-, two- or three-bedroom home behind the main house. California generally allows a detached ADU of up to 1,200 sq ft, and cities cannot block an ADU of at least 800 sq ft with 4-foot side and rear setbacks.
• Garage conversions — turning an existing garage into a legal studio or one-bedroom unit, often the quickest way to add a unit because the foundation, walls and roof already exist.
• Attached ADUs and JADUs — an addition to the house, or a junior ADU of up to 500 sq ft carved out of existing space with its own entrance and an efficiency kitchen.

Why homeowners in the San Gabriel Valley build ADUs

Most of our clients have one of three goals: rental income to help with a mortgage, a home for parents or adult children close by but with their own front door, or a long-term investment that adds a second legal unit to the lot. State ADU law (Government Code §§66310–66342) requires every city to approve qualifying ADUs ministerially — no public hearing — so a well-prepared application has a predictable path.

Our process — design, permits, construction

1. Free lot check. Send us your address. We look at lot size, the position of the house, setbacks, easements, the existing electrical service, sewer and water routing, and whether your parcel sits in a fire-hazard or hillside zone. We tell you honestly what size ADU fits.
2. Choose a plan. Start from one of our ready-made YRC designs (500 to 1,000 sq ft, all-electric) or have us draw a custom plan. Using a standard plan saves design time; a custom plan fits odd lots and special needs.
3. Site plan, engineering and energy. Every ADU needs a site plan for your parcel. We coordinate the structural/foundation design with a California-licensed engineer, the Title 24 energy report, and solar PV sizing where required for new detached units.
4. Permit. We submit to your city (or LA County for unincorporated areas like Rowland Heights), answer plan-check comments and track the application. If your city has a pre-approved plan program, we use it where it fits — see our city guides.
5. Construction. Our own crew builds under our B license: foundation, framing, roofing, plumbing, drywall, finishes and site work. Electrical — including any main-panel or service upgrade — is done in-house under our C-10 license.
6. Final inspection and move-in. We schedule inspections, close out the permit and hand over warranty information and equipment manuals.

Free quote — what we look at on your lot

No two backyards are the same, so we quote each ADU project individually after a free lot check. A written quote from YRC covers design coordination, engineering, permits and construction, and is based on what we find on your property:

• Size and type — a garage conversion, a JADU, an attached addition or a new detached unit each involve different scopes of work.
• Utilities — the route to the sewer line, water service, and whether the main electrical panel needs a service upgrade for an all-electric ADU.
• Site conditions — slopes, trees, tight side yards, demolition of an old garage, soils and access for equipment.
• City requirements — each city has its own plan-check and permit process; we check your city’s current requirements before we quote.
• Finishes and equipment — cabinets, flooring, windows, and the all-electric package (heat-pump water heater, ductless heat pump, induction range, range hood).

How long does it take?

A typical detached ADU moves through three phases. These are general ranges, not a promise — city workloads and plan-check corrections change them.

• Design and engineering: a few weeks with a standard plan; longer for a custom design.
• Permitting: state law requires cities to act on a complete ADU application within 60 days. Under AB 1332, a detached ADU application that uses a city pre-approved plan (or a plan identical to one already approved) must be approved or denied within 30 days.
• Construction: commonly several months for a detached unit, depending on size, inspections and weather; conversions are usually faster.

Pre-approved ADU plans and YRC plan designs

AB 1332 (2023) required every city and county in California to run a program to pre-approve ADU plans by January 1, 2025. Cities list approved plans and the designers who own them; homeowners who use one still need a site plan, but the review is faster. Yellow River Construction has prepared original all-electric plan designs for the Rosemead and Monterey Park programs. Status: YRC design — city pre-approval pending. They are not city pre-approved yet. Contact for pricing.

See all YRC ADU plan designs →

ADU rules by city

Each city writes its own ADU ordinance within the limits of state law. Our local guides explain the process, the official program pages and what to prepare:

• Rosemead ADU builder — ADU Standard Plans Program; site plan & design review before building plan check
• Monterey Park ADU builder — Designer-Owned Pre-Approved ADU Program
• Arcadia ADU builder — PAADU program, Arcadia EDGE permits
• San Gabriel ADU builder — 2024 ADU ordinance update
• Alhambra ADU builder — building-permit-only ADU review
• Temple City ADU builder — pre-approved plans + zoning clearance
• Rowland Heights ADU builder — unincorporated LA County, free county standard plans
• El Monte ADU builder — zoning clearance + building permit

All-electric by design

California’s energy code now favors heat pumps, so our designs are all-electric: a heat-pump water heater, a ductless mini-split heat pump for heating and cooling, an induction or electric range with a properly sized range hood, and solar-ready wiring. Because we hold a C-10 electrical license, we size the new loads, design the ADU sub-panel and handle any main service upgrade with the utility in-house.

Frequently asked questions

Do I need to live on the property?

State law currently does not allow cities to require owner occupancy for a standard ADU. A junior ADU (JADU) is different: the owner generally must live in either the main house or the JADU. Ask us about your situation.

Can I rent my ADU?

Yes, long-term rentals are allowed. Many cities, including Rosemead, prohibit renting an ADU as a short-term (vacation) rental — check your city’s ordinance.

Do I need to add parking?

Often not. State law waives ADU parking in many situations — for example, within one-half mile walking distance of public transit, or when you convert a garage. Some cities still require one space in other cases.

Can I use another designer’s pre-approved plan with YRC as the builder?

Yes. Pre-approved plans are owned by their designers, so you purchase the plan from that designer. We can then handle the site work, the permit coordination and construction.

Are YRC’s plans city pre-approved?

Not yet. Our designs are YRC designs with city pre-approval pending in Rosemead and Monterey Park. Any of them can also be permitted the regular way as a custom ADU.

Do you work in my city?

We are based in City of Industry and work throughout Los Angeles County, focusing on the San Gabriel Valley. If your city is not listed above, ask us.