Now Booking Fall 2026: Schedule Your Consultation
Detached ADU Builder in the Bay Area
Hamilton Exteriors is a detached ADU builder. We plan and build the separate dwelling: site, utilities, foundation, permits, construction, and final inspection. Serving the Bay Area and Northern California.
500+ projects
Since 2018
Limited Lifetime
Product Warranty
Get Your Free Quote
We'll call within 3–5 minutes to schedule your consultation.
Your information is private and secure
ADU certifications, brands, and contractor credentials
Customer-Service Obsessed
Responsive from consultation through project closeout
Architect and general contractor
One accountable team
Licensed, bonded, and insured
Verified business credentials
A detached ADU creates a separate dwelling without changing the main home's floor plan. Its location must support privacy, daylight, outdoor space, and a practical path from the street while leaving the rest of the property useful.
We start with the buildable area. Setbacks, easements, trees, slope, drainage, fire access, and utility routes can change the footprint and foundation. Measuring those conditions before design keeps the floor plan tied to the actual site.
Utility routes often decide whether a detached ADU fits the first location a homeowner chooses. We compare trench length, meter and sewer connections, grade, access, and required clearances before fixing the footprint. That early check can prevent a good floor plan from depending on a site connection that cannot be built as drawn.
How We Plan and Build a Detached ADU
The project moves from property feasibility to a permitted and inspected dwelling.
-
Confirm the Buildable Site
We measure the property and review setbacks, access, trees, drainage, fire conditions, utilities, and the relationship to the main home.
-
Design and Permit the ADU
We coordinate the footprint, floor plan, foundation, structure, energy documents, building systems, and agency submission package.
-
Build Through Final Inspection
Construction follows the approved set through site work, utility connections, framing, weather protection, interiors, inspections, and closeout.
Detached ADU Site Review
| Item | What We Review | Project Effect |
|---|---|---|
| Buildable area | Setbacks, easements, lot coverage, and trees | Sets the location and footprint |
| Access | People, equipment, materials, and fire access | Shapes the site plan and construction method |
| Utilities | Water, sewer, electrical, and data routes | Affects placement and underground work |
| Site conditions | Slope, soil information, drainage, and trees | Guides the foundation and grading scope |
| Privacy | Entries, windows, paths, and outdoor areas | Supports both dwellings |
Place the ADU Before Drawing the Rooms
The building location controls access, privacy, daylight, yard use, and utility length. We document the property first and test practical footprints. This keeps the floor plan connected to the conditions that will govern permits and construction.
Coordinate the Building and Utility Plan
A detached dwelling needs a complete structure and working services. The floor plan, foundation, sewer route, electrical capacity, water connection, heating, cooling, and ventilation must support each other. We coordinate these systems before the permit set is complete.
Carry One Scope Through Inspection
Site work, architecture, engineering, permits, utilities, and field construction affect the same decisions. Hamilton Exteriors carries the approved design through excavation, framing, interiors, agency inspections, and project closeout.
Detached ADU Financing Options
Detached ADU costs can include feasibility work, design, engineering, permit fees, utilities, the foundation, and construction. Financing is available with approved credit for eligible project costs. During your consultation, we explain available terms, payment timing, and which parts of your detached ADU project can be financed.
Ask about detached ADU financing during your consultation.
Call Now (650) 977-3351 Detached ADU Reviews
Verified public reviews from homeowners who hired Hamilton Exteriors.
Yaku Escobar
via Google
We worked with Hamilton Exteriors to build a small ADU in our backyard. from the beginning the process felt organized and clear. Alex Lee was very responsive and always kept us in the loop, especially during planning and inspections. The crew was consistent and respectful of the space which we appreciated since we were living there during the build. overall everything moved pretty smoothly and the final result looks exactly like what we had in mind. really happy with how it turned out.
Rafa Simons
via Google
My family hired Hamilton after seeing the neigbours new ADU, the whole team were super organized and tecnological and also very patient to undestand my needs before starting the construction. But what i like the best is that they are really preocupated with the final result and they kept us well inform with details and everything. Definitely recomend them.
H.T.
via Google
I had a great experience working with Hamilton exteriors. From start to finish, their team was professional, responsive, and detail-oriented. They made the entire process smooth and stress-free, keeping me updated every step of the way. The quality of their work really stands out. Everything was done efficiently and exceeded my expectations. If you’re looking for a reliable company that takes pride in what they do, I highly recommend them!
Jessica W.
via BBB
The team was professional, communicative, and completed the job in a timely manner. They kept me informed throughout the entire process and arrived as scheduled. The work was well supervised, and the crew paid close attention to every detail. They left the property clean and organized when the job was finished. Overall, the entire experience was smooth, stress-free, and exceeded my expectations. I would definitely recommend their services to others.
Frequently Asked Questions
Didn't find the answer to your question? Call Now (650) 977-3351
What makes a detached ADU different from an attached ADU?
A detached ADU stands apart from the main home. It needs its own foundation, weatherproof shell, utility connections, and site access. The separation can improve privacy, but it makes property planning and utility routing more important.
How do you choose the location for a detached ADU?
We compare buildable area, setbacks, easements, trees, drainage, fire access, privacy, daylight, and utility routes. A suitable location balances permit limits with daily use and practical construction access.
How are utilities connected to a detached ADU?
The design routes water, sewer, electrical service, and data from approved connection points. Distance, grade, sewer depth, panel capacity, and trench access affect the route and construction scope.
Does a detached ADU need its own foundation?
Yes. The foundation design follows the building loads, soil information, slope, drainage, and local requirements. The engineer may specify a slab, raised foundation, piers, or another site-appropriate system.
Can a detached ADU match the main home?
Yes. Roof form, windows, cladding, trim, and color can relate to the main home. The design can also use a compatible style when an exact match would limit the layout or site placement.
What happens before detached ADU construction starts?
We complete feasibility, design, engineering, energy documents, permit review, selections, and construction planning. Work starts after the required approvals and project-specific materials are ready.
Get Your Detached ADU Quote
Tell us about your project. We usually call within 3–5 minutes.
Related ADU Services
ADU Services by City
21634 Redwood Rd Unit F, Castro Valley, CA 94546
Serving 88 cities across the Bay Area, Greater Sacramento, and Central Valley. Explore all service areas →