A free site visit, a check of what your lot allows and a written, line-item price.
Get your free estimateFast, Reliable Home Addition Contractor Across San Francisco
A home addition in San Francisco typically costs between $180,000 and $520,000 depending on whether you’re adding a ground-floor bump-out, converting a garage, or going up with a full second story. Most permitted additions take 6 to 14 months from design to final inspection, with garage conversions and prefab ADUs running faster at 4 to 8 months. Lodgewick ADU San Francisco has worked on lots from the Outer Sunset to Bernal Heights, and we know that on a 25-foot-wide San Francisco parcel, the difference between a smooth build and a stop-work order comes down to party-wall notices, seismic review triggers, and staging logistics that most contractors don’t address until it’s too late. Call (707) 760-0502 for a free estimate and a written price before any work starts.
Key takeaways:
- San Francisco additions cost $180k – $520k depending on scope, lot, and seismic scope
- Party-wall notice is mandatory 15 days before touching a shared wall; missing it delays your permit
- Garage conversions in dune-sand neighborhoods like the Sunset and Richmond often trigger floodplain and geotech review
- SFMTA staging permits can add thousands; we price them in writing, not as a surprise change order
- Every Lodgewick project carries the 365-Day Done Right Promise, in writing, before a single nail is driven
Why Lodgewick ADU San Francisco Is San Francisco’s Preferred Home Addition Contractor Company
Lodgewick ADU Builders is the ADU company of the Kingswell family, established in 2010. The name means what it says: a lodge is a small house on a larger property, which is exactly what an ADU is. Russ Delmar leads the San Francisco Bay Area office, and our crews live and work in the same neighborhoods we build in – not dispatch from two counties away. We know that a Victorian in Noe Valley shares a wall with a neighbor who has a legal right to 15 days’ notice, and that a Sunset row house on dune sand needs a different foundation conversation than a hillside lot in Bernal Heights.
Homeowners in San Francisco who’ve been burned before tell us the same things: a contractor quoted one number on the phone, changed it at the door, then disappeared mid-project. The Kingswell Guarantee exists to end that pattern. Written price first. Real arrival window. Clean job site. Written guarantee on every project. If it’s not done right within 365 days, we come back and make it right, free.
Our Home Addition Contractor team handles room additions, second-story additions, sunroom additions, bathroom additions, garage additions, and bump-out additions across San Francisco. For the full scope of what we do and how we price, that page walks through each service. This one is about what’s different when the job sits on a San Francisco lot.
Second Story Addition Contractor in San Francisco
A second story addition contractor in San Francisco has to solve for something most cities never see: a 25-foot-wide lot with zero rear yard, a shared wall on one side, and a Planning Department that wants structural drawings tied to a soils report before they’ll even schedule your intake. Going up is usually the right move when you can’t go out – but it’s the most permit-heavy residential job in the city. Expect a second-story addition in San Francisco to run $280,000 to $520,000 depending on whether the lower floor needs seismic strengthening, whether you need a crane pickup from the street, and whether the existing foundation can carry the load.
Seismic upgrades drive the quote
In most pre-war San Francisco homes – and that’s most of the city’s housing stock – a second story triggers mandatory lateral retrofit on the lower floor. On a Richmond or Sunset garage-under home, that often means a steel moment frame, new hold-downs, and a foundation upgrade. If you skip the geotech report and Planning catches it, you get a stop-work order. We order the geotech first.
Crane staging and the SFMTA lane permit
On a Sunset corner lot with no rear yard, the crane picks from the street. That means a pre-paid SFMTA temporary no-parking lane closure, flaggers, and a traffic plan submitted with your permit package. We price that as a line item in the written quote, and we’ve never had a crane ticketed because we didn’t pay the permit.
Garage Addition Contractors in San Francisco
Garage addition contractors in San Francisco do more garage conversions than anywhere else in the Bay Area, because the city’s pre-war housing stock is full of underused garages and basements just waiting to become living space. A garage conversion into a one-bedroom ADU in San Francisco typically costs $180,000 to $320,000 when the garage is at grade and the structure passes seismic review without major upgrades. The same job on a hillside lot in Bernal Heights with a mandatory soils review, or in the Outer Sunset where floodplain review kicks in, can push closer to $380,000.
The party-wall notice changes your start date
If your garage shares a wall with the neighbor’s garage – common in Noe Valley and the Mission – San Francisco’s Department of Building Inspection requires a site-specific party wall notice delivered to each adjacent owner at least 15 days before work begins. Serve it late and Planning puts a hold on your permit while the calendar runs. We track that window in our project schedule and send the notice certified mail with proof of delivery.
Floodplain review on dune sand
Outer Sunset and outer Richmond garages sit on old dune sand, and many lots are mapped into a flood overlay even though it never looks wet. Planning’s advisory often requires raising the finished floor six inches above the mapped floodplain and reinforcing the slab-on-grade. We’ve done exactly that on 1940s garages, and the extra height also helps keep fog-driven moisture out of the living space.
Trusted Brands We Service in San Francisco
We regularly work with prefab and panelized systems from Boxabl, Plant Prefab, and Tuff Shed, and we specify James Hardie siding and trim on most San Francisco additions because it stands up to the marine air better than wood lap in the fog belt. If you’ve already chosen a prefab ADU brand, we’ll handle the site work, foundation, utilities, and the permit package so the factory-built shell drops onto a San Francisco-legal foundation. We keep local stock of common James Hardie profiles in Bay Area warehouses, which shortens lead times when a wall needs to close before the winter rains.
Common Home Addition Contractor Problems We See in San Francisco Homes
- Seismic retrofit underestimated: A pre-war garage in the Richmond often needs a steel moment frame and foundation upgrade. Contractors who skip the geotech report get a stop-work order when the hillside lot triggers a mandatory soils review.
- Party-wall notice missed: On a shared Victorian wall in Noe Valley, failing to serve the adjacent owner with 15 days’ notice delays demolition by weeks while the neighbor files a complaint. We serve notice before we even finalize the permit package.
- Staging on a zero-lot-line site: A second-story addition on a Sunset corner lot with no rear yard needs a crane pickup from the street. Without a pre-paid SFMTA lane closure, the crane is ticketed and materials sit on the sidewalk – which triggers a nuisance complaint from the block.
- Moisture from the marine layer: Fog-driven condensation in a converted garage will blister drywall and grow mold if the slab isn’t raised and the envelope isn’t ventilated. We install mechanically fastened EPDM membrane and raised slabs as standard on ground-floor conversions in the fog belt.
Pricing for Home Addition Contractor in San Francisco, CA
Here’s what we quote in San Francisco right now:
- Bump-out addition (add 80 – 150 sq ft to a kitchen or bath): $95,000 – $190,000
- Garage conversion to ADU (at grade, no seismic trigger): $180,000 – $320,000
- Garage conversion to ADU (hillside or floodplain overlay): $260,000 – $380,000
- Second-story addition (full floor, 600 – 900 sq ft): $280,000 – $520,000
- Sunroom addition (non-conditioned, no foundation upgrade): $70,000 – $140,000
What moves the number: whether your lot triggers a geotech or soils review, whether you share a wall, whether the existing foundation needs seismic strengthening, and whether we need a rented lane or parking space for staging. Those are line items in the written quote, not surprises at the door. Call (707) 760-0502 to schedule a free estimate – we’ll give you a real number in writing.
We Also Serve Cities Near San Francisco
While this page is written for homeowners in San Francisco, our crews also take on additions in Daly City, Sausalito, Emeryville, and San Bruno. Each of those cities has its own permit quirks – Daly City’s hillside review, Sausalito’s coastal-zone requirements – and we handle them the same way: written price, real arrival window, clean job site, written guarantee.
Serving San Francisco, CA - Our Local Coverage Area
We’re based in the San Francisco area and know this community well. Use the map below to see our service coverage - if you’re nearby, we can almost certainly help.
FAQs About Home Addition Contractor in San Francisco
The 15-day party wall notice must be delivered to every adjacent property owner at least 15 days before work begins on a shared wall, so we build that window into your schedule from day one. If you share a wall in Noe Valley or the Mission, count on at least 15 days added to the front of your project. Call (707) 760-0502 and we’ll map out your exact timeline, including the notice window.
Yes, if your lot has the buildable envelope and the existing foundation can carry the load, you can go up over the existing footprint and keep the rear yard. Most 25-foot lots in the Sunset and Richmond qualify, but the lower floor usually needs seismic strengthening. We’ll tell you in the first consultation whether your lot works – and we’ll show you the Planning math that proves it.
San Francisco’s noise ordinance allows construction from 7:00 AM to 8:00 PM on weekdays, but many neighborhoods have stricter conditions attached to the permit – especially near schools, hospitals, and on narrow streets where the DBI limits delivery hours. We post the permitted hours on every job site and our crews follow them exactly. Call (707) 760-0502 and we’ll tell you what hours apply to your specific block.
The Outer Sunset sits on old dune sand, and much of the neighborhood is mapped into a FEMA flood overlay even though it never looks wet. Planning’s advisory usually requires raising the finished floor six inches above the mapped floodplain and reinforcing the slab, which we’ve done on dozens of 1940s garages out there. It’s not a delay if you know it’s coming; we do.
We pre-pay an SFMTA temporary no-parking lane closure for the dates we need staging, post the signs, and keep all material inside the closed lane. On steep Bernal Heights blocks we’ve also used a tracked skid steer to move material without tearing up the driveway. It adds a line item to the quote, but it’s cheaper than a towed truck, a nuisance abatement, or an angry block – and we put it in writing before the job starts.
Written by Russ Delmar, Owner at Lodgewick ADU San Francisco, serving San Francisco since 2010.
