Free written scope consultation - allowances, timeline, and change-order rules on paper before a single trade is scheduled
CGI Home Additions & ADU: The San Francisco Owner’s Guide
CGI home additions and ADU projects in San Francisco typically run between $53,100 and $153,400 for a full addition, and $106,200 to $259,600 for a detached or attached ADU. We handle the construction side from the first inspection through final paint, including the framing, foundation, electrical rough-in, plumbing, and the finishes that make the new space feel like it was always part of the house. Most owners call us after living with the problem for months: the spare room is too small, the in-laws are visiting more, or the home office is now a nursery and someone is working from the dining table. We start with a written price before any work begins, so you know the full cost on paper, not a promise.
One note up front: Elmstead Remodeling San Francisco is an independent remodeling contractor. We’re not affiliated with CGI, but we work with CGI-compatible materials and specifications every week, and we know how their window, door, and exterior product lines integrate with San Francisco’s building requirements.
Which CGI Models This Applies To
When you’re planning a home addition or ADU in San Francisco, the CGI products most often specified are their impact-rated windows and doors, which are common in coastal and hillside neighborhoods where wind exposure and fog drive material choices. If your existing house has CGI windows or doors, the new addition should match the frame depth, glass package, and hardware finish so the transition doesn’t look like an afterthought.
The compatibility gotcha most owners miss: CGI’s architectural and impact-rated lines use different frame depths, and a mismatched window will sit proud or recessed in the wall. You can find the series name on a label inside the frame or on the lock hardware. If the label is painted over or faded, take a photo of the window edge and the glass corner etching, and call us at (831) 480-4497. We’ll identify the series before we write the proposal. For the OEM-versus-aftermarket decision, we recommend OEM CGI windows and doors when the addition is visible from the street or when you’re matching existing units for insurance reasons. For interior doors and secondary windows, quality aftermarket equivalents from brands like KraftMaid and Cambria often save 15 to 20 percent without changing the look. For countertops, Silestone and Cambria both offer profiles that hold up well in San Francisco’s damp, cool climate.
Styles & brands we work with
Signs Your CGI Home Additions & ADU Is Failing
Most “failed” additions and ADUs aren’t structural failures. They’re the result of original work that didn’t account for San Francisco’s specific conditions: marine air, sloped lots, dense neighboring homes, and city permitting quirks. Here are the signs we see most often when we’re called in to assess an existing addition or ADU:
- Fog-damaged window seals or condensation between panes. In neighborhoods like the Sunset, Richmond, and the Presidio, persistent marine fog creates a condensation cycle that eats gas-filled window seals. If you can wipe the inside but the cloud stays, the seal failed and the insulated glass unit needs replacement.
- Uneven floors or a door that swings closed on its own. San Francisco homes sit on everything from sand to serpentine rock. A small addition that settles differently than the main house will show itself in door alignment within the first two wet seasons.
- Drafty corners where the addition meets the original structure. The seam between old and new is the most common air and water intrusion point. If you feel cold air near the transition wall in winter, the flashing or the transition framing wasn’t done with the care San Francisco fog demands.
- Mold or a musty smell in the ADU after rain. A properly built ADU in San Francisco should stay dry through winter. If it doesn’t, the issue is almost always a missing or incorrectly lapped moisture barrier at the roofline or the lower wall plate.
- Electrical circuits that trip when the addition and the main house are both running. Older San Francisco homes were built for different loads. An addition that shares a panel without a proper service upgrade will show its limits the first time the microwave, the space heater, and the washer all run at once.
See the difference
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After
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AfterReplacement Cost & What’s Included
Home addition and ADU pricing in San Francisco is a function of three things: foundation work, accessibility to the site, and finish level. Here’s how the ranges break down for the work we do:
- Home addition (full room, attached to the existing structure): $53,100 – $153,400. This includes foundation, framing, roofing integration, windows and doors, insulation, drywall, electrical, plumbing rough-in where needed, and finish work.
- ADU construction (detached or attached, with kitchen and bath): $106,200 – $259,600. This includes permits, site work, utility connections, fixtures from Kohler and Moen, cabinetry from KraftMaid or Wellborn, countertops from Cambria or Silestone, and all finish carpentry.
- Garage conversion to living space: $35,400 – $94,400. The widest range in San Francisco, driven almost entirely by the condition of the existing slab and whether the garage was built before or after seismic code updates.
Every proposal includes a written price before any work starts. That price lists the materials by brand name, the labor, the permit costs, and the clean-up. If the city inspector flags something and a change is required, we write the change order in plain language and you approve it before any extra work happens. Our 365-Day Done Right Promise covers the completed project: if something’s not right, we make it right. No fine print, no argument.
DIY or Call Us?
For a home addition or ADU in San Francisco, DIY isn’t a realistic option. These projects involve structural framing, foundation work, seismic anchoring, electrical service, and plumbing that all require city permits and inspections. A failed inspection means rework, and rework means paying twice. If you’re handy, the tasks you can reasonably take on are paint, trim, and hardware selection. Everything inside the walls and below the floor should be handled by a licensed contractor who pulls permits and schedules the inspections.
That said, there’s real value in knowing how the process works before you hire anyone. We walk every client through the permit sequence, the inspection points, and the daily schedule before we sign a contract. You’ll know which days the crew arrives, what they’re doing, and when the inspector is coming. If you’re thinking through a project, call (831) 480-4497 and ask for Graham. We’ll talk through the scope and give you a written price. The estimates are free.
FAQs
A properly permitted and built home addition or ADU in San Francisco should last 50 years or more before needing major structural work, though the finish materials (paint, flooring, fixtures) will need refreshing every 10 to 15 years. Marine air accelerates wear on exposed metal and exterior wood, so coastal neighborhoods like the Outer Sunset and Outer Richmond should expect more frequent exterior maintenance than inner-city neighborhoods like Noe Valley or the Mission. Call (831) 480-4497 for a site-specific assessment.
It depends on what’s failing. Fogged windows, drafty seams, and settling doors can often be repaired without tearing down the structure. Foundation movement or widespread moisture intrusion usually means partial demolition and rebuilding. We’ll tell you which category your project falls into after the first walkthrough, and the written price covers exactly what we find. Call (831) 480-4497 to schedule a walkthrough.
A full home addition in San Francisco typically takes 4 to 8 months from permit approval to final inspection. An ADU typically runs 6 to 12 months. The permitting process itself in San Francisco can add 3 to 9 months before construction starts, depending on the neighborhood review process and whether your lot has any additional planning requirements. We handle the permit filing, and we’ll give you a realistic timeline in writing before any work begins.
We order CGI-compatible windows and doors directly from the supplier as part of the project, which means the lead time is built into the schedule and the warranty is registered in your name. Stocking windows isn’t practical in San Francisco because every opening is a different size and every neighborhood has different wind and exposure ratings. When we order, we specify the exact series, frame depth, and glass package that matches your existing CGI units. Call (831) 480-4497 and we’ll walk the window schedule with you.
Tell me what the room needs to do, and we’ll figure out the rest from there.
If you’ve been living with a too-small room, a drafty old addition, or a garage that’s just storing boxes you never open, call us at (831) 480-4497. We’ll schedule a walkthrough, talk through the scope, and get you a written price before any work starts. The estimate is free, the crew wears shoe covers and lays down drop cloths, and a live person answers the phone 24/7. That’s Graham Stein’s crew at Elmstead Remodeling San Francisco.
Written by Graham Stein, Owner, Elmstead Remodeling San Francisco at Elmstead Remodeling San Francisco, serving San Francisco and nearby areas.
