With 10% pre-1940 in Redwood City, many properties have room for an ADU alongside the original structure. UV degradation and thermal cycling crack composition shingles 3-5 years faster than coastal cities. Original stucco on 1950s ranches develops extensive hairline cracking from expansion/contraction. often make ADU construction the ideal time to address deferred maintenance on the primary residence.
Now Booking Fall 2026: Schedule Your Consultation
ADU Builder in Redwood City
500+ projects
Since 2018
Limited Lifetime
Select Product Warranties
Get a FREE ADU Consultation
We'll contact you in 3-5 minutes to discuss your ADU project.
Your information is private and secure
For detailed ADU pricing factors, use our 2026 Bay Area ADU cost guide.
Your next step
Start Your ADU Consultation Online
Share your property and project goals. Our team will discuss feasibility, design, permits, and the next planning step.
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
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.
Redwood City's housing stock spans 10% pre-1940, 30% 1940-1960, 30% 1960-1985. Architectural styles range from 1950s-60s ranches and tract homes in Woodside Plaza and Redwood Village to turn-of-century Victorians and Craftsmans downtown. 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.
Redwood City's Community Development Department has created a supportive framework for ADU construction. The city offers pre-application consultations, online permit tracking, and a dedicated ADU information page with fee schedules and design guidelines. Redwood City has also adopted San Mateo County's pre-approved ADU plans, which can reduce plan review time to as little as 30 days. Hamilton Exteriors leverages these pre-approved options when they fit a client's needs and designs custom solutions when they don't.
Redwood City's residential neighborhoods offer varied ADU opportunities across different lot sizes and terrain. The flatland neighborhoods of Downtown, Stambaugh Hale, Palm Park, and Friendly Acres feature 1940s to 1960s homes on 5,000 to 7,000 square foot lots suited for compact detached ADUs. Farm Hill and Woodside Plaza have larger lots of 6,500 to 9,000 square feet that accommodate full-sized 1,000 to 1,200 square foot units. Emerald Hills, perched in the western hills, offers lots of 10,000 to over 20,000 square feet with premium views but requiring specialized hillside construction.
Redwood City's central Peninsula location creates strong ADU rental demand from workers at Oracle, Box, Electronic Arts, and Stanford Health Care. One-bedroom ADUs rent for $2,200 to $2,800 per month, while two-bedroom units reach $3,000 to $3,500. The city's vibrant downtown, Caltrain access, and mild climate make Redwood City ADUs attractive to young professionals and remote workers seeking more space than apartment living provides.
San Mateo County offers several ADU-supportive programs that benefit Redwood City homeowners. The county's Second Unit Amnesty Program helps legalize unpermitted ADUs, and the HEART of San Mateo County loan program provides financing assistance for ADU construction. Redwood City has also reduced utility connection fees and waived certain impact fees for ADUs under 750 square feet. Hamilton Exteriors helps clients navigate these programs to reduce overall project costs.
Neighborhoods We Serve
ADU Across Redwood City Neighborhoods
Local planning starts with the site, neighborhood context, access, and applicable city review.
Downtown Redwood City
Downtown Redwood City homeowners frequently choose Hamilton Exteriors for adu. With 10% pre-1940 in Redwood City, many properties have room for an ADU alongside the original structure. With Redwood City's Peninsula warm pocket: summer highs 80-95°F, winter lows 38-48°F, material selection in Downtown Redwood City requires local expertise.
Roosevelt
In Roosevelt, homes are predominantly turn-of-century Victorians and Craftsmans downtown. UV degradation and thermal cycling crack composition shingles 3-5 years faster than coastal cities. Our crews are familiar with Roosevelt's architectural character and building requirements.
Downtown
Downtown Redwood City's revival has transformed the area into a walkable urban center with restaurants, theaters, and Caltrain access. Residential lots of 4,500 to 6,500 square feet with older single-family homes offer garage conversion and compact ADU opportunities. The walkability score and transit access make downtown ADUs among the easiest to rent in the city.
Emerald Hills
Emerald Hills sits in the western foothills with lots of 10,000 to 25,000 square feet and panoramic bay views. The hillside terrain requires engineered foundations and retaining walls, but the larger lot sizes accommodate generous ADU footprints. ADU tenants here enjoy privacy, quiet, and views that command premium rents of $2,800 to $3,500 per month.
Redwood Shores
Redwood Shores is a planned waterfront community with 1980s to 2000s homes on lots of 4,000 to 6,000 square feet. The neighborhood's proximity to Oracle and other tech campuses on the lagoon creates consistent tenant demand. Compact detached ADUs and garage conversions work best on the tighter lot configurations typical of this planned community.
Woodside Plaza
Woodside Plaza features midcentury ranch homes on 6,500 to 9,000 square foot lots near Woodside Road and Highway 280. The generous lot depths and flat terrain make this one of Redwood City's most efficient neighborhoods for detached ADU construction. Many properties have existing detached garages that can be converted or replaced with a larger ADU structure.
Farm Hill
Farm Hill's 1950s and 1960s homes on lots of 6,000 to 8,500 square feet occupy a gentle hillside with bay views from upper elevations. The neighborhood's established character and proximity to Roy Cloud School make it attractive to family tenants. Detached ADUs of 600 to 900 square feet work well on Farm Hill's moderately sized lots with their slight grade changes.
Friendly Acres
Friendly Acres is a quiet residential neighborhood with 1950s homes on 5,500 to 7,000 square foot lots. The flat terrain, regular lot shapes, and established utility infrastructure make ADU construction straightforward and cost-effective. The neighborhood's family-friendly streets and proximity to local parks attract stable long-term tenants.
Stambaugh Hale
Stambaugh Hale features a mix of 1940s and 1950s homes on 5,000 to 6,500 square foot lots near downtown. The neighborhood's walkability to Sequoia Station and downtown amenities increases ADU rental appeal. Garage conversions and small detached ADUs are the most common ADU types here, making efficient use of the compact lot sizes.
Mount Carmel
Mount Carmel's tree-lined streets and 1930s to 1950s homes on 5,500 to 7,500 square foot lots create a established residential setting near Stafford Park. The neighborhood's architectural mix of Craftsman and midcentury styles calls for ADU designs that complement the existing streetscape. Hamilton Exteriors designs ADUs that respect Mount Carmel's residential character while maximizing livable space.
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 Premium Market
ADU Costs in Redwood City
$210,000–$450,000
Median home value in Redwood City: $1,750,000
Prices reflect Redwood City's premium market and San Mateo 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.
How much does an ADU cost in Redwood City?
ADU costs in Redwood City typically range from $150,000 to $350,000 depending on size, finishes, and whether it's a new build or garage conversion. With median home prices at $1,750,000, an ADU can add significant value. We provide free consultations with detailed estimates.
Can I build an ADU on my property in Redwood City?
California's ADU laws make it possible to build on most residential lots in Redwood City. San Mateo County has streamlined the permitting process. We evaluate your property's potential during our free consultation, including setbacks, utility access, and local zoning.
What types of ADUs can I build in Redwood City?
In Redwood City, you can build detached ADUs (up to 1,200 sq ft), garage conversions, attached additions, and junior ADUs (up to 500 sq ft). Many homeowners in Downtown Redwood City are choosing detached ADUs for rental income or multi-generational living.
Do I need a permit for an ADU in Redwood City?
Yes. Redwood City requires building permits for all ADU construction. The Community Development Department processes ADU applications with a streamlined review track. The city provides an ADU resource guide and pre-application consultation to clarify requirements before formal submission. Hamilton Exteriors handles the complete permit process from site assessment through final inspection.
What ADU types can I build in Redwood City?
Redwood City allows detached ADUs up to 1,200 square feet, attached ADUs, garage conversions, and JADUs up to 500 square feet. The city also permits an ADU and JADU on the same single-family lot. Two-story detached ADUs are allowed where zoning permits, giving homeowners on smaller lots the option to build up rather than out.
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
Serving 88 cities across the Bay Area, Greater Sacramento, and Central Valley. Explore all service areas →