We design and build modern ADUs for Bay Area living that blend efficiency, style, and seamless integration with your existing property.
Tailored project design approach, specifically created for your home.
We handle all city approvals and paperwork to ensure a stress free, on time process.
Quality construction using modern materials and experienced local crews.
Turnkey results so your ADU is ready to live in, rent out, or welcome guests.
Real ground-up ADUs we've designed and built across the Bay Area. No prefab, no shortcuts.
Millbrae, CA
A ground-up Spanish-revival detached ADU with hand-troweled white stucco, a clay-tile roof, arched entry, and a hand-set Moroccan tile niche, opening to a beamed, barrel-vaulted interior with walnut cabinetry and waterfall quartz.
Los Altos, CA
A completed detached ADU in Los Altos with a shaker kitchen with quartz counters and a tile backsplash, a fully tiled bath, mini-split climate control, and sliding glass doors onto the lawn.
Real reviews from Bay Area homeowners we’ve built for.
“I am so happy to find ADU San Mateo. The crew are nice, professional, doing a great job while pay attention to details, all with a good price. Highly recommend!”
“Finished work in a timely fashion. Quick to respond.”
“Excellent service highly recommended”
“ADU San Mateo went above and beyond our expectations. They were with us every step of the project, making the experience easy and headache free. ADU San Mateo has great attention to detail and abundance of carpentry knowledge. They always answered our calls and ensured the job site was clean and safe before ending the workday. The team was very professional, clean, and respectful. We contracted ADU San Mateo to build our ADU unit and cannot be happier with the outcome. Would definitely recommend to anyone looking for cost-effective get it right the first time company. Definitely would use for our future projects.”
“Dependable, responsive, quality workmanship and dedication to getting the project completed timely and on or under budget. They treated our home as if it was their own. The outcome exceeded my expectations. Would recommend to my friends and family.”
“I would highly recommend ADU San Mateo to all my friends and family. The crew is efficient, polite and hardworking. They are easy to work with and very competitive with pricing. We would definitely recommend and hire again for future projects.”
“Such exceptional work done, I am beyond pleased with the results! Paid close attention to detail and I was always kept informed. High quality work and excellent service gave us the results we expected. I was completely impressed with their professionalism and customer service. I highly recommend this business!”
“I HIGHLY recommend Eli and his team for any home remodeling projects. They did my staircase and completely did what I have envisioned. I am a perfectionist, so I am glad I met them. They are very detailed oriented, very punctual, and there were no delays. He advised me what’s the best route, up to code, and provided recommendations tweaks on my design. I provided a 3D rough draft sketch to them, the measurements were 100% accurate. I can guarantee you that you won’t be disappointed, as I went through roughly 10 contractors and FINALLY found the right team. I am looking forward to seeing how my kitchen tiles turn out.”
“They were responsive and efficient and easy to work with.”
BusinessRate’s Benchmark awards rank local businesses on their Google review record. In June 2026 we placed third among construction companies in Central San Mateo.
Pick your type, layout, bedrooms, bathrooms, and size, then get an instant estimated price range for your build. No prefab, just fully custom, ground-up builds.
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Starting at $250K+
ADU type
Layout style
Bedrooms
Bathrooms
Approximate size
Budget
Seamless ADU design and construction backed by transparent communication, local expertise, and licensed professionals.
We assess your goals and property to determine the best ADU plan.
Our team develops detailed plans and aligns design with your budget.
We handle all city approvals to keep your project moving smoothly.
Our builders bring your ADU to life with quality and precision.
We finish interiors and deliver your ADU ready for move-in.
Our ADUs are designed for efficiency, comfort, and long term value, delivering faster builds, stronger construction, and designs tailored to your lifestyle.
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cost savings through design
Budget reductions during design and planning
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licensed & insured professionals
All projects are completed by licensed, insured, and locally approved teams.
Local Expertise
trusted Bay Area builders
We navigate local codes, zoning, and permits with confidence
Insured
licensed & protected professionals
All projects are fully covered for safety and reliability
No matter why you’re adding an ADU, we make the process simple, smooth, and tailored to your vision.
Build a durable, compliant, renter-ready ADU that earns income effortlessly.
Create a flexible, accessible, peaceful space for family.
Increase your home’s value fast with a high-quality ADU that enhances your property.
Compare our full-service ADU builds to contractors and prefab vendors and see why homeowners choose us.
| Typical Contractor | Prefab Vendor |  | |
|---|---|---|---|
| Full Design & Engineering | No | No | Yes |
| Complete Permit Handling | No | Yes | Yes |
| Custom Architecture | Yes | No | Yes |
| Local Zoning Expertise | No | No | Yes |
| Transparent Fixed Pricing | No | No | Yes |
| Energy-Efficient Systems | Yes | Yes | Yes |
| On-Time, On-Budget Delivery | No | No | Yes |
| Move-In Ready Finish | No | Yes | Yes |
Providing reliable, high-quality services across your region.
Elie AlChaer
Founder & Licensed General Contractor
Elie AlChaer is the founder of ADU San Mateo. He spent his career delivering over $2 billion in commercial and luxury construction across the Bay Area and Dubai, and is a licensed California general contractor.
He started ADU San Mateo after watching too many homeowners hire cheap and pay for it twice: blown timelines, rework, budgets that unravel. His answer was to study the entire ADU process end to end and break it into phases, so you only commit to what moves your project forward, one step at a time.
Here are some common questions along with their answers to help clear up any confusion.
Let’s discuss your goals and find the best ADU solution for your property.
Get a free ConsultationGuides, permitting insight, and build stories from our San Mateo and Santa Clara County projects.
7 min read
Why two identical-looking ADUs on the same street can price very differently: the site conditions, utility work, and finish decisions that move the number most.
Read more →
5 min read
Three ways to add a second unit, three very different sets of trade-offs. How to tell which one your property is actually suited to before you spend anything on design.
Read more →
6 min read
Design, plan check, permit, inspections: a plain-English walkthrough of the stages every Bay Area ADU goes through, and the three things that cause most of the delays.
Read more →Tell us about your property and goals, and we’ll take it from there.
(650) 200-2040 · Monday to Friday 8AM-6PM
3 E 3rd Ave, Suite 200, San Mateo, CA 94401
License #1145539
