How to Find an ADU Builder in California—and Compare Their Bids
People always ask me to recommend the best ADU builder in California, and I’m like… “It’s complicated.”
Some of my favorite builders are small, local contractors who stay busy (and the really great ones know they should avoid getting too busy). And nobody loves to hear that my favorite builders might not specialize in the kind of ADU you want to build. want to serve your area, or even have room for you in their schedule.
So when someone asks, “Who’s the best ADU builder?” I want to help them answer a more useful question: Who’s the best builder for my property, my budget, and my project?
That means defining your scope of work (which is a whole process, not just one sentence scribbled on a napkin), finding qualified contractors who actually want your job, getting bids for the same scope of work, and understanding the differences before you choose.
I’m Ryan O’Connell, the host of How To ADU where I’ve released hundreds of videos about ADU rules in California and manage a Facebook Group with over 150,000 California homeowners building in their backyards and converting parts of their homes into apartments. Here’s the process I recommend—and why I’ve partnered with Realm Home to help homeowners through it.
Affiliate disclosure: How To ADU has a paid partnership with Realm Home, and I earn a referral commission when you use the links in this article.
How do I find an ADU contractor near me who will actually bid?
First of all, there’s a big difference between starting off your questions and research with a builder versus doing your homework ahead of time so you have a solid understanding of your project, a well-defined scope of work, and a good sense of how much it will cost.
If you start by chatting with a builder and you don’t really know how much it’s going to cost, you sound a lot like a tire-kicker. Even if you’re a very serious person and you’re ready to spend more money than you’ve ever spent on anything in your whole life, you are using the same language as a tire kicker who is just asking for free advice and the builders have a hard time knowing the difference between you and the tire-kickers.
Many good builders get steady work through architects, designers, past clients, and referrals. A homeowner building one ADU may have a harder time getting their attention, especially while the project is still taking shape.
So it helps if you can give contractors a clear starting point in your first outreach:
Your city and the type of ADU you’re considering
The approximate size and intended use (rent to a stranger, move mom in, adult kid, etc.)
Whether you already have plans or permits
Any work you also want done on the main house at the same time
Your target budget and timeline (you don’t have to spell this out if you want to avoid negotiating against yourself but you can indicate that you’re already qualified for a loan and getting bids as part of that process, or other ways to indicate that you understand this is real money)
Known challenges with access, utilities, or existing structures
A clear project description helps both sides decide whether a conversation makes sense. And it makes you look like a real buyer.
Now having said that, it can be hard to know all this if it’s your first time hiring a general contractor for a full build. And that’s why our sponsor Realm Home has a free call with you where they can educate you about your options and rough cost estimates for different versions of your project.
A lot of homeowners ask me if they should convert their garage, tear down and replace it, build on top of it, do an addition, etc. Thanks to Realm, you can schedule a free call and get those questions answered with real data for your specific zip code today.
Why I don’t just publish a list of my favorite ADU builders
If I recommend one small contractor to thousands of YouTube viewers, they will suddenly get more inquiries than they can handle.
Some homeowners are ready to build. Others are still exploring whether an ADU is possible. Those early questions are reasonable, but answering them takes time.
Then, once that contractor signs a few projects, their schedule fills up. The recommendation becomes less useful for everyone who calls afterward.
That’s why I like having a partner with a broader contractor network and people who can help homeowners prepare before requesting bids.
How Realm helps you find an ADU builder
Realm Home helps bridge the gap between “I’m interested in an ADU” and “I’m ready to choose a contractor.”
You can start with a free call to discuss your property, goals, basic cost estimates, and options. That conversation helps you define the scope before chasing builders.
When you’re ready for bids, Realm matches your project with three vetted general contractors, coordinates the bidding process, and helps you compare their proposals. Contractor matching and bid review are core parts of Realm’s service.
You can also bring a bid from a builder you found yourself.
That’s useful if you already have a recommendation from a friend, architect, or neighbor but want help understanding how their proposal compares.
Start with a free Realm consultation through How To ADU.
Even with plans, getting contractors to respond can be hard
Christina Gibson had plans for her garage conversion and had already started contacting ADU contractors. Getting someone to call back was still a challenge.
Realm helped her meet three contractors and compare their approaches.
“So, they were very responsive. They met on time.”
— Christina Gibson, Realm customer, 14:43 in our interview
She ultimately chose a contractor based on communication and fit, as well as price. Meeting several options gave her a chance to make that decision for herself.
Video: Garage Converted to a Lucrative ADU
What does getting ADU bids through Realm cost?
When you come from How To ADU, the first call is free and if you like their approach, then you can pay a $300 deposit to get 3 bids from vetted GCs. If you hire one of Realm’s builders, that fee comes back as a credit.
Confirm the current fee, credit conditions, and availability for your property during the free call, before you pay - make sure you’re getting the How To ADU pricing.
Even if you ultimately choose your own builder, I think there can be real value in having other bids to compare. They help you ask better questions, identify missing work, and have a more informed conversation about price.
They may also give you room to negotiate. That doesn’t guarantee savings, but it gives you more information than a single proposal.
“That money was well spent”
Dan and Kristin Romo wanted to stay on the property they’d called home for more than 20 years. They converted and expanded their detached garage into an ADU, initially housing their children and grandchildren, with a plan to eventually downsize into it themselves.
Getting started meant figuring out who to hire—and in what order.
“That money was well spent because we had no idea where to start.”
— Dan Romo, Realm customer, 13:43 in our interview
Realm helped them explore the numbers and introduced three builder options. After meeting those options, they found the team they wanted to work with.
Dan and Kristin also shared their family’s ADU journey with Business Insider in August 2023, including how they financed the garage conversion and created a home for their daughter and grandchildren.
Video: Downsizing in Retirement Thanks to Accessory Dwelling Units (ADUs)
The video and Business Insider article describe their experience at the time, including an older promotion and grant program. Confirm current offers and funding availability separately.
How to compare ADU contractor bids
Three bids won’t tell you much if each contractor is pricing a different project.
Give each builder the same plans and project description, then compare what they’ve included, excluded, or left open.
Design and permits: Who handles drawings, engineering, revisions, applications, and fees?
Site preparation: Are demolition, excavation, access work, and debris removal included?
Foundation and structure: Is the proposal based on the same drawings and assumptions?
Utilities: What trenching, connections, and service upgrades are included?
Finishes: Are cabinets, counters, flooring, fixtures, and installation included?
Appliances: Are purchase and installation included?
Exterior work: What happens to landscaping, paving, decks, and disturbed areas?
Schedule: When can work begin, and who will supervise it?
Changes: How are additional work and price changes documented and approved?
Pay particular attention to allowances: amounts set aside for things you haven’t selected yet.
A low allowance for cabinets or fixtures can make a bid look attractive while leaving you with additional costs when you make your selections.
An exclusion isn’t automatically a problem. You just need to understand it and budget for it.
How to choose an ADU contractor before signing
A referral is a starting point. You should still understand who you’re hiring.
California’s Contractors State License Board recommends checking the contractor’s license, checking references, verifying insurance, and putting the project’s materials and expectations into a written contract. Read CSLB’s homeowner guide.
Ask about recent ADU projects, especially work similar to yours. A detached backyard unit, a garage conversion, and an ADU above a garage can involve different challenges.
Useful questions include:
Have you completed ADUs like mine in this area?
Can I speak with recent clients?
Who will supervise construction and communicate with me? (many “builders” are more like sales people who then hire out the work and rarely show up to your job site in person)
How many projects does your team handle at once?
What work is excluded from this proposal?
Who coordinates with local agencies for permits like sewer, water and electrical?
What assumptions could change the price or schedule?
Pay attention to how clearly the contractor answers. You’ll be working together for months, and communication matters.
Questions homeowners ask about finding an ADU builder
These questions reflect concerns raised in the How To ADU community, including finding contractors for small projects, coordinating design and construction, and understanding what a bid covers.
How do I find an ADU contractor near me who will actually bid?
Start with contractors who serve your city and build your type of project. Send a concise project description and explain the status of your plans, budget, and timeline.
Ask about availability before spending time on a detailed proposal. A referral from a designer, past client, or a service such as Realm can help introduce you to contractors interested in the work.
How do I find a builder for a small ADU or garage conversion?
Ask specifically about comparable projects. Some contractors prefer larger new builds; others regularly handle conversions and smaller units.
For an existing structure, explain what is known about its condition and permit history. That helps the builder assess the work they may be taking over.
Do I need plans before requesting ADU bids?
You can have early conversations about feasibility and budget before your plans are complete.
A detailed construction bid needs a clearer scope. Ask each contractor what drawings and specifications they need, and distinguish a preliminary estimate from a proposal based on defined work.
Who coordinates between my ADU designer and contractor?
Clarify that before signing either agreement. Ask who answers construction questions, handles drawing revisions, and responds when field conditions differ from the plans.
Also ask which services are included in the design fee and which require additional payment. Approved plans don’t necessarily mean every question during construction has been resolved.
Should I choose the cheapest ADU builder?
Compare the scope before comparing totals. A lower price may reflect different finishes, missing work, or assumptions that another builder has priced differently.
Once the bids cover comparable work, consider references, communication, availability, and how the contractor plans to run your project.
Finally, look at the payment schedule and ask yourself if the builder has a realistic idea of how long your project will take. If they’re front-loading their payments and promising to be done in 3 months, you have a good sense that this is somebody who doesn’t mind starting your job and then taking forever to finish because they already got a lot of your money. If on the other hand, they have a realistic range for construction and don’t get fully paid out until they’re done with the project, then you’ve got a payment schedule that incentivizes them to stick with it and finish your job.
Can Realm review a bid from a builder I already found?
You can bring your own bid into the process. Tell your advisor what you already have and ask how they can help review and compare it.
You don’t have to discard a good personal referral to get another perspective. And sometimes you can use the Realm bids to negotiate on your existing bid - so it’s still a win. And sometimes Realm will even add your builder to their network because they’re always looking for good ADU Builders!
A practical next step toward building your ADU
I want How To ADU viewers and readers to have somewhere useful to go when they’re ready to move forward.
Realm gives homeowners a place to ask early questions, access vetted contractors, and get help understanding bids. They also provide ongoing support and an escalation path when issues arise. Ask your advisor what that support covers for your project.
No vetting process can promise a trouble-free build. But help with the search, comparison, and follow-through can make a complicated process easier to navigate.
Start with your property and your goals. Get clear about the scope. Compare bids carefully. Then choose a builder who fits the project.