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Sunset & Richmond
San Francisco's largest residential neighborhoods. Rows of single-story homes built 1930s–1960s, typically 1,000–1,400 sq ft on 25-by-100-foot lots.
PACIFICA-BASED CONTRACTOR — CSLB #1041528
Home Additions in San Francisco — Expanding a Home That Was Built for a Different Era
Rear expansions on Victorian row houses, second-story additions on Sunset tract homes, and hillside builds. Design-build with structural assessment first.
Why Local Expertise Matters
San Francisco Additions Are Different—We Know How
In most Peninsula cities, a room addition starts with a simple question: how much backyard can you use? In San Francisco, the question is different. Most residential lots are 25 feet wide. The house fills the full width. There’s no side yard. The neighbor’s wall is inches away — or it is your wall, shared across a property line. The only directions to expand are toward the rear of the lot or up.
San Francisco’s permitting process also differs from every other city in our service area. Building expansions go through both SF Planning and the Department of Building Inspection (DBI). SF Planning reviews against the Residential Design Guidelines and conducts a 30-day neighborhood notification. That notification period gives neighbors the opportunity to raise concerns and, in some cases, file for Discretionary Review.
ACI is a design-build general contractor based in Pacifica. We build room additions throughout San Francisco, from the Sunset and Richmond to the Victorian and Edwardian row houses of the Mission, Noe Valley, and Bernal Heights. We handle structural assessment, design, permitting through both Planning and DBI, and construction with our own crew.
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Based In Pacifica
188 Clarendon Rd. — serving San Francisco and the Peninsula since 2018
Neighborhoods
Where We Build in San Francisco
- 📍Mission, Noe Valley & Bernal
Victorian and Edwardian row houses — two- and three-story wood-frame buildings on narrow lots with shared party walls.
- 📍Bernal Heights & Potrero Hill
Hillside neighborhoods with sloped lots, engineered foundations, retaining walls. Views translate directly into property value.
- 📍Excelsior & Ingleside
Post-war construction similar to Sunset/Richmond, often at lower property values with varied lot configurations.
- 📍The Haight & Western Addition
Victorian and Edwardian housing stock similar to Mission and Noe Valley. Strong Design Guidelines sensitivity.
- 📍Diamond Heights & Outer Mission
Diamond Heights offers hillside lots with view potential. Outer Mission features post-war and multi-family housing with varied lot sizes.
- 📍Not Sure?
Every lot is different. Call (650) 224-3052 and describe your home and neighborhood. We'll tell you what's structurally and permitting-wise feasible.
Investment
What Room Additions Cost in San Francisco
San Francisco room additions cost more than identical scope in Peninsula cities — typically 15 to 30 percent more — due to higher permit fees, access constraints on narrow lots, and the additional SF Planning review layer.
*All ranges reflect Peninsula market conditions — varies by scope, site conditions, and finish level
Rear Ground-Level Addition
250–500 sf — family room, kitchen, or primary suite at rear
$87K – $162K+Second-Story Addition (Tract)
600 sf on Sunset/Richmond single-story homes
$240K – $420K+Dormer Addition
Attic conversion to bedroom, bathroom, or office
$62K – $125K+Primary Suite Addition
350–500 sf rear expansion
$200K – $400K+Victorian Seismic Retrofit
Foundation upgrade on older brick/concrete foundations
$30K – $80K+
All ranges include design, structural engineering, permitting, and construction. The largest variables are site conditions and existing structure complexity. We provide detailed cost estimates after the structural assessment.
Our Process
How We Build Room Additions in San Francisco
Structural Assessment
We evaluate your home's foundation, framing, existing systems, and lot constraints. This is where we identify what's feasible and what the existing structure needs before construction.
Design
Plans that reflect your home's structural realities and your local zoning requirements. Design-build means our team stays integrated from concept to completion.
Permitting
We submit plans to the local planning and building departments and manage the entire review process. We file regularly in San Francisco and know the approval timeline.
Construction
Our crew handles all structural work — foundation reinforcement, framing, connections. We build it right the first time, with inspection at each stage.
Completion
Interior finishes, exterior integration so the addition looks like it was always part of the home, final inspections, and certificate of occupancy.
Why ACI
Why San Francisco Homeowners Choose ACI
Based on the Peninsula
We're at 188 Clarendon Road in Pacifica, serving San Francisco and neighboring communities. We know the local building departments, the soils, the housing stock, and the permitting timelines.
We Do Structural Work
Foundation reinforcement, framing, shear walls, seismic connections — our crew handles this directly. No coordination gaps with separate engineers and contractors.
Engineering First
We bring the structural engineer in before design starts. Plans reflect your home's structural realities from day one — no surprises during construction.
Design-Build Model
One contract, one team for design, engineering, permitting, and construction. Eliminates coordination gaps and keeps your project on track.
CSLB #1041528
Licensed GC — Class B
Bonded & Insured
Family-Owned