Many South San Francisco homes — especially 1920s-40s worker cottages and bungalows on Sign Hill and Old Town — were built when families and living patterns were smaller. deferred maintenance on older worker cottages in Old Town with decades of lead paint layering often surface during addition projects, and we address them as part of the build.
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Home Addition Contractor in South San Francisco
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For second-story pricing factors, use our Bay Area second story addition cost guide.
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Share your property and expansion goals. We will discuss the existing home, feasibility, design, permits, and the next planning step.
Home addition brands and contractor credentials
Customer-Service Obsessed
Responsive from consultation through project closeout
Architect and general contractor
One accountable team
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Addition Services 
Start With the Home Expansion Path You Need
Second-Story Additions
Vertical expansion planned around the existing foundation, framing, stair location, roof changes, seismic work, utilities, and occupied-home logistics.
Room Extensions
Attached ground-floor space coordinated with the existing plan, foundation, roof, openings, drainage, building systems, and architectural character.
Guest Houses and Detached Living Space
A separate project path for detached guest space. Independent dwelling units also require ADU-specific feasibility and permit review.
Whole-House Remodels
Coordinated work across most rooms and building systems when the project changes the home beyond one added space.
Local Expertise
Home Additions in South San Francisco: What Local Homeowners Need to Know
Get Your QuoteSouth San Francisco's housing stock spans 15% pre-1940, 30% 1940-1960, 25% 1960-1985. Architectural styles range from 1920s-40s worker cottages and bungalows on Sign Hill and Old Town to 1950s-60s ranches in Westborough and Winston Manor. Each era and style presents different home additions requirements — from material compatibility to structural considerations. Our crews know what to expect before they arrive on site.
Neighborhoods We Serve
Home Additions Across South San Francisco Neighborhoods
Local planning starts with the site, neighborhood context, access, and applicable city review.
Avalon
Avalon homeowners frequently choose Hamilton Exteriors for home additions. Many South San Francisco homes — especially 1920s-40s worker cottages and bungalows on Sign Hill and Old Town — were built when families and living patterns were smaller. With South San Francisco's Split: eastern bayside 62-78°F summers, western hills 55-68°F, material selection in Avalon requires local expertise.
Sunshine Gardens
In Sunshine Gardens, homes are predominantly 1950s-60s ranches in Westborough and Winston Manor. deferred maintenance on older worker cottages in Old Town with decades of lead paint layering often surface during addition projects, and we address them as part of the build. Our crews are familiar with Sunshine Gardens's architectural character and building requirements.
Westborough
Westborough homeowners expand mid-century homes with additions that modernize layout and add space. Second-story additions capture views while ground-floor expansions preserve yard in this established South San Francisco neighborhood.
Sign Hill
Sign Hill additions in South San Francisco require hillside engineering expertise. We evaluate slope, soil, and foundation conditions before designing additions that safely and attractively expand your living space.
Buri Buri
Buri Buri's family homes gain value from thoughtful additions. We handle design, engineering, and construction under one contract. Many Buri Buri homeowners add second-story primary suites or rear family rooms.
Project Management How Hamilton Exteriors
How Hamilton Exteriors
Manages Your Home Addition
Existing-Home Assessment
We review the foundation, framing, roof, utilities, drainage, access, and likely connection points before the addition design advances.
Design and Permit Coordination
Our team coordinates the layout, architecture, structural engineering, energy documents, permits, comments, revisions, and approved plans.
Addition Construction
We manage site protection, structural connections, foundation, framing, weatherproofing, building systems, finishes, inspections, and documented changes.
Integration and Closeout
We check connections between new and existing work, complete final inspections and the punch list, and review applicable warranty terms.
Google rating 4.6 ★ from 47 public reviews
Homeowner Reviews of Our Construction Work
Public feedback from remodeling and related construction projects.
K
Kevin L
via Google
We hired them for a bigger renovation. Alex was very responsive, which I appreciated. We changed a couple requirements during the job and they worked with us on it without making it complicated. Overall, everything went pretty smooth and their quality of work is solid. I recommend them highly!
J
Jacob Rothwell
via Google
Alex Li helped me with my basement remodeling, they were super efficient, and the work came out better than I could’ve ever imagined! Thank me later!
M
Maan D
via Google
Had Hamilton Exteriors do a full kitchen renovation. Natasha helped a lot with scheduling and coordination which made things easier on our end. We got regular updates and didn’t feel left in the dark at any point. The team paid attention to details and made sure everything was installed properly. the whole process felt pretty smooth and the kitchen came out really clean. happy with the final result
L
Lekan Ajayi
via Google
This service was good and very efficient, all remodeling was done to liking. Jacob was a great worker and helped with answering questions that was needed. Would recommend to others.
Google rating: 4.6/5 from 47 public reviews
Read reviews on Google Mid Market
Home Additions Costs in South San Francisco
$180,000–$400,000
Median home value in South San Francisco: $1,100,000
Prices reflect South San Francisco's mid 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 Home Expansion Paths
Swipe to compare all options.
| Feature | Second Story | Room Extension | Guest House | Whole-House Remodel |
|---|---|---|---|---|
| Relationship to home | New level above | Attached ground-floor space | Detached structure | Existing home transformed |
| Main structural focus | Foundation capacity, framing, and roof | New foundation and connection | New foundation and separate structure | Existing framing and building systems |
| Site impact | Keeps most yard area | Uses ground-floor footprint | Uses a separate site area | Usually stays within the home footprint |
| Early planning focus | Stairs, structure, roof, and occupancy | Layout, setback, roof, and drainage | Access, utilities, setbacks, and use | Phasing, systems, structure, and relocation |
| Dedicated guide | Second story | Room extension | Guest house | Whole-house remodel |
Addition Financing
Plan Your Home Addition With Approved Credit
Financing may be available for eligible room extensions, second-story additions, and larger remodeling projects with approved credit. During planning, we review the scope and explain current lender programs, terms, amounts, and payment timing.
Ask which current options fit your home addition project.
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 a home addition cost in South San Francisco?
Home additions in South San Francisco typically cost $200-$500 per square foot depending on scope and finishes. A second story addition usually runs $250,000-$500,000. With median home prices at $1,100,000 in South San Francisco, adding space is often more economical than moving. Free consultations available.
Can I add a second story to my home in South San Francisco?
Most single-story homes in South San Francisco can support a second story addition with proper structural engineering. We evaluate your foundation, framing, and local zoning during our free consultation. Many homes in Old Town have successfully added second stories.
How long does a home addition take in South San Francisco?
Most home additions in South San Francisco take 3-6 months from permit to completion. Second story additions are typically 4-6 months. We handle all San Mateo County permits and manage construction so you have one point of contact.
Does Hamilton Exteriors handle permits for additions in South San Francisco?
Yes. We handle all permitting for home additions in South San Francisco and San Mateo County — architectural plans, structural engineering, and city submissions. We work with South San Francisco planning departments regularly.
Can I live in my home during the addition in South San Francisco?
In most cases, yes. We phase construction to minimize disruption. For second story additions, there may be a brief period where certain rooms are inaccessible. We create a detailed plan before starting so you know exactly what to expect.
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.
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21634 Redwood Rd Unit F, Castro Valley, CA 94546
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