With 8% pre-1960 in Antioch, many properties have room for an ADU alongside the original structure. premature shingle granule loss and curling from extreme heat cycling (40°F nights to 100°F+ days) often make ADU construction the ideal time to address deferred maintenance on the primary residence.
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For local cost factors and planning, read our ADU construction cost guide for Antioch.
For detailed ADU pricing factors, use our 2026 Bay Area ADU cost guide.
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Start Your ADU Consultation Online
Share your property and project goals. Our team will discuss feasibility, design, permits, and the next planning step.
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Customer-Service Obsessed
Responsive from consultation through project closeout
Architect and general contractor
One accountable team
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ADU Services 
Start With the ADU Service Your Property Needs
Detached ADUs
A new backyard structure planned around the lot, setbacks, access, utilities, fire requirements, privacy, permits, and construction logistics.
ADU Design
Architect-led feasibility and plans shaped by the property, existing home, program, code constraints, utilities, and budget.
ADU Permits
Plan-check coordination for architecture, engineering, energy documents, utility requirements, agency comments, revisions, and inspections.
Garage Conversion ADUs
Conversion planning for the existing slab, framing, ceiling height, fire separation, insulation, utilities, windows, access, and permits.
Antioch's housing stock spans 8% pre-1960, 22% 1960-1979, 25% 1980-1999. Architectural styles range from 1970s-80s ranch-style tract homes in older neighborhoods to 2000s-2020s two-story stucco production homes in Lone Tree. Each era and style presents different adu requirements — from material compatibility to structural considerations. Our crews know what to expect before they arrive on site.
Antioch experiences extreme Central Valley-influenced summers with temperatures regularly exceeding 100 degrees, creating significant thermal stress on building materials. Our ADU designs for Antioch incorporate high-performance insulation, energy-efficient HVAC systems, and strategic window placement to ensure year-round comfort without excessive utility costs.
The housing stock in Antioch spans from 1970s-era subdivisions near downtown to newer master-planned communities in the eastern hills, with median home prices around $620,000. The existing housing stock presents diverse opportunities for ADU construction, from garage conversions in older neighborhoods to detached new builds in communities with larger lots.
The City of Antioch Building Department processes residential permits through its Community Development office, with typical turnaround of 4-6 weeks for standard projects. Hamilton Exteriors (CSLB #1078806) navigates the ADU permitting process in Antioch, ensuring compliance with both state ADU laws and local zoning requirements for efficient project approval.
Neighborhoods We Serve
ADU Across Antioch Neighborhoods
Local planning starts with the site, neighborhood context, access, and applicable city review.
Sand Creek
Sand Creek homeowners frequently choose Hamilton Exteriors for adu. With 8% pre-1960 in Antioch, many properties have room for an ADU alongside the original structure. With Antioch's Summer highs average 93°F with 20+ days over 100°F, material selection in Sand Creek requires local expertise.
Prewett Ranch
In Prewett Ranch, homes are predominantly 2000s-2020s two-story stucco production homes in Lone Tree. premature shingle granule loss and curling from extreme heat cycling (40°F nights to 100°F+ days) often make ADU construction the ideal time to address deferred maintenance on the primary residence. Our crews are familiar with Prewett Ranch's architectural character and building requirements.
Lone Tree
Lone Tree in Antioch has strong rental demand, making ADUs an excellent investment. Many homeowners use their ADU for family members or generate $2,000-$3,500 in monthly rental income.
Deer Valley
Lot configurations in Deer Valley often accommodate detached ADUs in rear yards with separate entrances for privacy. We design layouts that maximize living space while meeting setback requirements.
Black Diamond
Garage conversions are popular in Black Diamond where existing two-car garages provide a cost-effective starting point for ADU construction at roughly 30% less than new builds.
Project Management How Hamilton Exteriors
How Hamilton Exteriors
Manages Your ADU Project
Property Feasibility
We review the lot, setbacks, existing structures, access, utilities, drainage, fire requirements, and likely permit path.
Design and Permit Coordination
Our team coordinates architecture, engineering, energy documents, utility requirements, submittals, comments, revisions, and approved construction documents.
ADU Construction
We manage site work, foundation, framing, building envelope, mechanical, electrical, plumbing, finishes, inspections, and documented changes.
Final Inspection and Closeout
We coordinate corrections and final inspections, complete the punch list, and organize closeout and applicable warranty information.
Google rating 4.6 ★ from 47 public reviews
ADU Project Reviews
Verified public reviews from homeowners who hired Hamilton Exteriors.
Y
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.
R
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
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!
J
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.
Google rating: 4.6/5 from 47 public reviews
Read reviews on Google Budget Market
ADU Costs in Antioch
$150,000–$375,000
Median home value in Antioch: $620,000
Prices reflect Antioch's budget market and Contra Costa County labor rates. Actual costs depend on home size, materials, and project complexity. We provide free, itemized estimates with no hidden fees.
Get Your EstimateCompare Broad ADU Project Paths
Swipe to compare all options.
| Feature | Detached ADU | Garage Conversion | Junior ADU |
|---|---|---|---|
| Location | Separate backyard structure | Within an existing garage | Within the primary home |
| Existing shell | New foundation and structure | Existing shell requires verification | Existing conditioned structure |
| Main feasibility focus | Lot, access, setbacks, and utilities | Structure, slab, height, and utilities | Interior layout and required shared systems |
| Privacy planning | Separate building and entrance | Entrance and yard relationship | Connection to the primary home |
| Dedicated guide | Detached ADUs | Garage conversions | Start with an ADU consultation |
ADU Financing
Plan Your ADU Project With Approved Credit
Financing may be available for eligible ADU construction projects with approved credit. During feasibility and scope planning, we explain current lender programs, terms, amounts, and payment timing that may apply to the design and construction path.
Ask which current options fit your ADU project scope.
Call Now (650) 977-3351 Frequently Asked Questions
Didn't find the answer to your question? Call Now (650) 977-3351
What areas do you serve?
We serve Northern California across three regions: the San Francisco Bay Area, Greater Sacramento, and the Central Valley. Our published guides cover 14 counties and 88 cities. Our Castro Valley and Sacramento offices support local estimating, permit coordination, and project planning across these regions.
How does billing and financing work?
Financing may be available for eligible projects with approved credit. Available terms depend on lender approval, project scope, and current programs. Your project manager can review the options that apply before work begins. We also accept checks, ACH, and major credit cards.
Are you licensed and insured?
Yes. Hamilton Exteriors holds CSLB License #1078806, active general liability coverage, and the required contractor bond. We also hold GAF Master Elite and James Hardie Elite Preferred credentials. We can provide current proof of coverage before work begins.
Do I need a permit for my exterior project?
Permit requirements depend on the project scope and local jurisdiction. Hamilton Exteriors coordinates required applications, plan documents, corrections, and inspections. Permit fees and allowances appear in the proposal before construction begins.
Why Build an ADU in Antioch?
An ADU can provide separate living space for family or a potential rental. Whether it fits your Antioch property depends on the usable lot area, layout, access, utilities, and applicable requirements. Review those conditions before choosing a detached unit or conversion. Do not treat rental income or a payback period as guaranteed.
How Much Does an ADU Cost in Antioch?
An Antioch ADU needs an estimate for its type, size, and site. A garage conversion and a new detached unit have different structural and utility work. Ask for design, engineering, site preparation, utility connections, permit costs, and finishes to be identified separately. Confirm allowances and exclusions before comparing the total price.
Why Choose Hamilton Exteriors as Your Antioch ADU Builder?
### Architect-Led Design-Build Most ADU contractors in Antioch are tradesmen-only. They build what an architect designs, and if something doesn't work during construction, you pay for change orders. Hamilton Exteriors is different. Alex Hamilton Li is both a licensed architect and a general contractor. He oversees every project from initial design through final inspection. This integration eliminates the gaps between design and construction, resulting in fewer surprises and a finished ADU that m
How much does an ADU cost in Antioch?
An ADU in Antioch costs $150,000 to $375,000 depending on the type (Hamilton Exteriors 2024-2026 project data). Junior ADUs (JADUs) run $150,000 and up. Garage conversions cost $150,000 to $200,000. Detached ADUs range from $200,000 to $375,000. Permit fees add $5,000 to $12,000. These numbers include design, engineering, permits, and construction.
Does Antioch allow ADUs?
Yes. Antioch allows ADUs on all single-family residential lots. California state law (AB 68, SB 13, AB 881) overrides most local zoning restrictions. The City of Antioch offers pre-approved ADU plans to streamline the process. You can find details on the Antioch pre-approved ADU page.
Your Next Step
Plan Your Project With a Clear Scope
Financing may be available with approved credit for eligible projects.
Tell us about your project. We usually call within 3–5 minutes to schedule the next step.
21634 Redwood Rd Unit F, Castro Valley, CA 94546
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