ADU Contractor in Los Angeles
Detached ADUs, junior ADUs, and garage conversions - designed, permitted, and built by one family-owned team from La Cañada Flintridge.
Licensed, Bonded & Insured · CSLB #1139272 | 10-Year Workmanship Warranty | 50+ Years Combined Experience | $1M General Liability | Financing Available
Western Building Solutions is a licensed ADU contractor serving Los Angeles County from our office in La Cañada Flintridge. We build detached ADUs, attached ADUs, junior ADUs, and garage conversion ADUs - handling feasibility, design, engineering, permitting, and construction under one contract.
An ADU is one of the few improvements that adds a second income stream to a property rather than just improving the one you live in. It is also the most heavily regulated thing we build, which is why the permitting work matters as much as the framing. We know how La Cañada Flintridge, Pasadena, Glendale and LA County each handle ADU plan check, and we know which lot conditions quietly kill a project before it starts - utility easements, slope, sewer capacity, fire access on the hillside streets. You can see completed ADUs in our project gallery or read more about our team on our about page.
What Is an ADU?
An ADU, or accessory dwelling unit, is a self-contained second home on the same lot as an existing house. It has its own kitchen, bathroom, sleeping area, and separate entrance, and it can be detached, attached to the main house, or converted from existing space like a garage. ADUs are sometimes called granny flats, in-law units, casitas, or backyard cottages. In California, state law requires cities to allow them on nearly every single-family residential lot.
Types of ADU We Build
| Type | Typical size | What it is |
|---|---|---|
| Detached ADU | 500 – 1,200 sq ft | A standalone structure in the backyard, fully independent of the main house |
| Attached ADU | 400 – 1,000 sq ft | Built onto the existing house, sharing one wall but with its own entrance and utilities |
| Garage conversion ADU | 350 – 600 sq ft | The existing garage footprint converted into a permitted dwelling |
| Junior ADU (JADU) | Up to 500 sq ft | Carved out of the existing house, with its own entrance and an efficiency kitchen. May share a bathroom with the main house |
Which type makes sense depends less on preference than on your lot. Setbacks, existing structures, slope, and where your sewer lateral runs will usually narrow the options for you before you ever pick a floor plan. That's what the feasibility check is for.
The standard we build to
Complete home renovation - Los Angeles
Primary bathroom with freestanding tub and double vanity - Glendale
ADU Kitchenette - Los Angeles
How Much Does It Cost to Build an ADU in Los Angeles?
There is no honest single number, and we'd rather tell you that than quote one we can't stand behind. ADU cost in Los Angeles is driven far more by your lot than by your finishes - slope, soil, how far the unit sits from the sewer lateral and the electrical panel, and whether your panel needs upgrading can swing the same 800-square-foot design by six figures. What we can tell you is exactly what determines your number, and we'll give you a real one after we walk your property.
| ADU type | Relative cost | Why |
|---|---|---|
| Junior ADU (up to 500 sq ft) | Lowest | Uses existing space and often existing plumbing |
| Garage conversion ADU | Low to moderate | Existing slab, walls and roof; depends on slab condition and ceiling height |
| Attached ADU (400 – 800 sq ft) | Moderate | Shares a wall and sometimes utilities with the main house |
| Detached ADU (600 – 800 sq ft) | Higher | New foundation, framing and independent utility runs |
| Detached ADU (1,000 – 1,200 sq ft) | Highest | Two-bedroom scale; hillside lots and long utility runs push it further |
What Drives ADU Cost
- Foundation and site work - hillside lots, retaining walls, and poor soil are the biggest single swing factor in our area
- Utility runs - distance from the main house to sewer, water, gas, and the electrical panel, plus whether the panel needs upgrading
- Converting vs. building new - whether you're reusing existing space or starting from a slab
- Finish level - an ADU built to rent and an ADU built for a parent are not the same budget
- Fire sprinklers - if the main house has them, or the unit size triggers the requirement
- Soft costs - design, engineering, Title 24, school fees, and city impact fees
Does an ADU Pay for Itself?
That depends on rent in your neighborhood and how you financed it, and we won't pretend to a number we can't stand behind. What we can tell you honestly: a permitted ADU adds appraisable square footage and a rentable unit, both of which show up in a valuation. An unpermitted one adds neither, and becomes a problem in escrow. That difference is the strongest financial argument for doing it properly the first time.
We don't quote ADUs over the phone, and we don't publish ranges we'd have to walk back once we've seen your lot. What we do instead: walk the property, check the setbacks and utility runs, and give you an itemized estimate with soft costs broken out separately from construction - so you can see exactly where the money goes rather than a single number. Financing is available. Book your free feasibility check and we'll tell you what your lot will actually support.
How Long Does It Take to Build an ADU in California?
A detached ADU in Los Angeles typically takes 10 to 16 months from first meeting to final inspection. Design and engineering take 4 to 8 weeks, permitting in Los Angeles averages 8 to 12 weeks, and construction runs 4 to 8 months depending on size and site conditions. Garage conversions move faster - often 4 to 7 months total.
| Phase | Typical duration | What happens |
|---|---|---|
| Feasibility and site check | 1 – 2 weeks | Setbacks, utilities, slope, and zoning confirmed before you spend on design |
| Design and engineering | 4 – 8 weeks | Floor plans, elevations, structural, Title 24 energy compliance |
| Plan check and permitting | 8 – 12 weeks | Submittal, city corrections, resubmittal, permit issued |
| Foundation and framing | 6 – 10 weeks | Site prep, utilities trenched, slab poured, framing and roof |
| Rough trades and inspections | 4 – 6 weeks | Plumbing, electrical, HVAC, insulation, drywall |
| Finishes and final | 6 – 10 weeks | Cabinets, tile, fixtures, paint, final inspection, certificate of occupancy |
California law requires cities to approve or deny a complete ADU application within 60 days, and as of January 2026 a city must tell you within 15 business days whether your application is even complete. Those deadlines only help you if the submittal is right the first time - every correction cycle adds weeks. A clean first submittal in a slow city routinely beats a sloppy one in a fast city.
How We Build Your ADU
1. Free feasibility check - we walk the lot, confirm setbacks and utility access, and tell you honestly what your property will support before you spend anything.
2. Design and itemized estimate - floor plan, elevations, and a line-by-line number with soft costs separated from construction costs.
3. Engineering and Title 24 - structural calculations and energy compliance prepared in-house or with our licensed partners.
4. Plan check and permits - we submit, respond to city corrections, and manage resubmittals through to permit issuance.
5. Construction - one dedicated project manager, a protected site, and a weekly written update.
6. Final inspection and certificate of occupancy - we don't hand over keys until the unit is legally habitable and signed off.
An ADU touches more agencies than any other residential project. Handing you a permit set and wishing you luck isn't a service - we carry it through to the certificate of occupancy.
What ADU Owners Say
Every review below is from an ADU we designed, permitted, and built. Names and cities are used with permission.
★★★★★
"We originally wanted to add square footage to our existing house for my in-laws to move in, but after going over the pros and cons with Western Building Solutions, we went with their suggestion of building an ADU. They helped us understand that if our parents ever did move out, no one would be occupying the space, but with an ADU, we'd still be able to utilize the space by renting it out and getting an extra source of income. None of the other companies we reached out to even suggested that. Steven and Leo really opened our eyes to different possibilities and were nothing less than professional and responsible. Most importantly for us, they finished the project in the timeline they promised. I recommend everyone reach out to WBS before making their final decisions on home renovations."
- Hakop A.,
Detached ADU, 2025
★★★★★
“My husband and I reached out to Western Building Solutions for a time sensitive remodel of our kitchen in our ADU for our new tenant to move in and they DELIVERED! Called in on a Sunday, expecting to leave a voicemail but to my surprise they picked up and Jay and Matt showed up on my doorstep 2 hrs later because of the urgency.
Discussed our budget and design plans and they instantly got to work. Fast forward 2 weeks later, the job is finished and both my tenant and I couldnt be happier with their work.”
- Suzy H.,
Detached ADU Kitchen, 2024
Why Los Angeles Homeowners Choose Us for Their ADU
Plenty of companies will sell you an ADU. Fewer will tell you before you pay them that your lot won't take one, or that the version you want costs substantially more than the version that fits. We do the feasibility work first because a project that dies at plan check is worse for us than one we never started. Being based in La Cañada Flintridge means we've been through ADU plan check in these specific cities repeatedly - and we know which ones read the state law generously and which ones fight it.
- Family-owned, based at 430 Foothill Blvd in La Cañada Flintridge
- Feasibility checked before design fees, not after
- Design, engineering, permitting and construction on one contract
- Licensed, bonded and insured - CSLB #1139272, $1M general liability
- Itemized estimates with soft costs shown separately from construction
- 10-year workmanship warranty
- Selected for the La Cañada Flintridge Chamber of Commerce Rising Business Program
Learn more about our team and how we work.
California ADU Laws and Permits: What You Need to Know
Yes, ADUs require a building permit in every California city. But state law has stripped most of the discretion cities used to have. Local agencies must allow at least one ADU on nearly every single-family lot, must approve or deny a complete application within 60 days, and cannot impose an owner-occupancy requirement. As your licensed general contractor, we prepare the drawings, submit the application, handle corrections, and meet the inspector on site.
| Rule | What it means for you |
|---|---|
| Minimum size guarantee | Cities must allow at least an 800 sq ft ADU regardless of local lot-coverage or FAR limits, with 4-foot side and rear setbacks |
| Maximum size | Most residential lots support up to 1,200 sq ft, subject to local ordinance |
| 60-day approval | Cities must approve or deny a complete application within 60 days. As of January 2026, they must also confirm completeness within 15 business days |
| Owner occupancy | Cannot be required for standard ADUs. As of January 2026 this also applies to junior ADUs |
| Parking | No replacement parking can be required when you convert a garage into an ADU |
| Separate sale | Some jurisdictions now allow an ADU to be sold separately as a condominium, if the city has opted in |
| Multifamily lots | Up to eight detached ADUs are permitted on qualifying multifamily properties |
In practice, the state rules set the floor and the city sets the friction. La Cañada Flintridge runs ADU applications through its own Building & Safety Department and the ConnectLCF portal. Pasadena, Glendale and Burbank each have their own plan-check queue and their own habits about what they'll flag. Unincorporated areas - Altadena, La Crescenta, parts of the foothills - go through LA County Building and Safety, which is a different process again. Hillside lots anywhere in this area add fire-access and grading review on top.
State law changes most years. The summary above reflects the rules in effect as of August 2026 - we confirm the current requirements for your specific city at the feasibility stage rather than relying on what was true last year.
ADU Construction Across Los Angeles County
We build ADUs throughout the San Gabriel Valley and the eastern San Fernando Valley, including La Cañada Flintridge, Pasadena, South Pasadena, Glendale, La Crescenta, Montrose, Altadena, Burbank, Sherman Oaks, Studio City and Encino. Because an ADU takes a year and dozens of site visits, proximity matters more here than on any other job we do - our office on Foothill Blvd puts most of these projects within a twenty-minute drive.
Not sure whether your lot qualifies, or whether you're in our service area? Call (855) 853-6100 or send us a message.
ADU Construction faqs
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ADU stands for accessory dwelling unit. It's the legal term California uses for a second, self-contained home on the same lot as an existing house. You'll also hear them called granny flats, in-law units, casitas, backyard cottages, or guest houses - these all describe the same thing.
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There's no honest single number for an ADU, because site conditions move the cost more than the design does. Slope, soil, distance from the sewer lateral and electrical panel, and whether the panel needs upgrading can swing the same floor plan dramatically. Junior ADUs and garage conversions are the least expensive routes; detached new construction is the most. We walk your lot and give you an itemized estimate with soft costs shown separately from construction.
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Plan on 10 to 16 months from first meeting to final inspection for a detached ADU in Los Angeles. That breaks down as 4 to 8 weeks of design and engineering, 8 to 12 weeks of plan check and permitting, and 4 to 8 months of construction. Garage conversions are faster, typically 4 to 7 months total.
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Yes. Every ADU in California requires a building permit, and depending on the project it may also need electrical, plumbing, mechanical, and grading permits. California law requires cities to approve or deny a complete ADU application within 60 days. We prepare the drawings, submit the application, handle city corrections, and meet the inspector on site - you don't file anything yourself.
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State law requires cities to allow at least 800 square feet with four-foot side and rear setbacks, regardless of local lot-coverage limits. Most residential lots can support up to 1,200 square feet depending on the local ordinance. Junior ADUs, which are carved out of the existing house, are capped at 500 square feet.
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No. California has permanently removed the owner-occupancy requirement for standard ADUs, and as of January 2026 that also applies to junior ADUs. You can build an ADU and rent out both units, or rent the ADU while living in the main house.
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Yes. ADUs can be rented on a long-term basis anywhere in California. Short-term rentals under 30 days are a different question - many cities, including several in our service area, restrict or prohibit them for ADUs specifically. We'll confirm your city's rules during the feasibility check so you're planning around the real numbers.
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In some jurisdictions, yes. California law now permits cities to allow ADUs to be sold separately as condominium units, but the city has to opt in and the process involves a condo map. Most cities in our area have not adopted it yet. Treat separate sale as a possible future benefit rather than something to count on.
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Your existing home is not reassessed when you add an ADU. The county assesses the value of the new construction and adds it to your existing assessed value - so you pay additional tax on the ADU itself, not on the whole property at current market value. Your county assessor is the authority here, and it's worth a call before you commit.
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Yes. Western Building Solutions is a licensed California general contractor, CSLB license #1139272, carrying a $25,000 contractor's bond and $1 million in general liability coverage. Every ADU we build is backed by our 10-year workmanship warranty. You can verify our license directly on the California Contractors State License Board website.
Find Out What Your Lot Will Support
Before you spend a dollar on design, let us walk the property and tell you what's actually buildable - setbacks, utilities, slope, and the real cost range for your specific lot. Free, no obligation, and no sales pitch. If your lot won't work, we'll say so.