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Cover Home Additions & ADU: The San Francisco Owner’s Guide
Home additions and ADU construction in San Francisco typically run $53,100 to $153,400 installed, depending on square footage, site access, and whether you’re building up, out, or converting existing space. We work with owners who have a Cover product or warranty documentation on an existing addition and need structural work, interior finishing, or a full ADU build to match their original investment. Most owners reach out after noticing a failing component in an existing addition: a leaking tie-in at the roofline, a sagging floor system, or an underpermitted ADU conversion that needs to be brought to code.
We’re an independent San Francisco remodeling contractor. We’re not affiliated with Cover, but we understand their product documentation and know how to work within the warranty and spec framework you already have. Curtis Lane runs the crew here, and he’ll be the first to tell you that a home addition is not a parts swap. It’s a structural project. But when an addition or ADU fails, there’s usually a specific assembly that failed first, and that’s where we start.
Key Takeaways:
- San Francisco addition and ADU work runs $53,100 – $153,400, with ADU construction starting higher due to utility runs and foundation requirements.
- What fails first is usually the roof tie-in, the foundation connection, or the moisture barrier at the wall intersection.
- We provide a written price before any work starts. No numbers move at the door.
- Every completed project carries the 365-Day Done Right Promise in writing. If it fails inside a year, we come back and correct it at no charge.
Which Cover Models This Applies To
Cover’s home addition products fall into a few general categories, and the compatibility question is usually about the point where the addition meets the original structure. If your Cover documentation lists a specific product line for a prefabricated wall or roof assembly, we match materials and fastening schedules to that spec. If you have a Cover-backed ADU kit, the compatibility concern is the foundation system and the utility rough-in points, which have to align with San Francisco’s setback and daylight-plane rules.
Here’s the gotcha we see most often in San Francisco: a Cover addition spec written for a flat lot doesn’t account for the slope and soil conditions you find in neighborhoods like Glen Park or the hills above Noe Valley. The product itself is fine. The site adaptation is where things go wrong. We verify the foundation plan against actual soil conditions before we order or install anything. That’s not paperwork for its own sake. A spec drawn for sandy loam behaves differently on serpentine clay, and in San Francisco you might have both on the same block.
On the OEM-versus-aftermarket question for Cover components: for structural members, headers, and connection hardware, we use only what the engineering documents call for. Aftermarket equivalents are fine for finish work like trim, interior doors, and cabinet hardware, but we don’t substitute on anything load-bearing. The material spec exists for a reason, and the building inspector will want to see it matches what’s on the permitted drawings.
Styles & brands we work with
Signs Your Cover Home Additions & ADU Is Failing
- A crack running diagonally from a window or door corner. This usually means differential settlement at the foundation connection. In San Francisco’s expansive clay soils, the original footing may not have been sized for the site’s actual conditions, even if it matched the Cover spec on paper.
- Water staining at the ceiling where the addition roof ties into the main house. The roof-to-wall flashing at that intersection is the single most common failure point on any addition. Fog-driven moisture in the Outer Sunset and Richmond District finds its way in through even a small gap.
- A floor that bounces or feels soft in one specific area. This points to undersized joists or failed bridging. We’ve opened up floors in Visitacion Valley and found original material spans that never should have passed.
- Doors or windows that stick seasonally. In an ADU, this often traces back to inadequate ventilation and moisture management. Wood framing swells, and the issue compounds every year until the opening no longer functions properly.
- Electrical flicker or outlets that trip intermittently in the addition. Older addition wiring, especially in converted garages through the Mission and Bernal Heights, wasn’t always run to handle the load of a full ADU. The subpanel may be undersized for what the space is now being used for.
Replacement Cost & What’s Included
A full home addition in San Francisco carries an installed range of $53,100 to $153,400. ADU construction runs higher: $106,200 to $259,600, driven by foundation work, separate utility runs, and San Francisco’s planning and permitting requirements. A garage conversion lands between $35,400 and $94,400. These are real numbers for San Francisco’s market, where material delivery, labor rates, and permit fees all carry a premium over surrounding counties.
Here’s what moves the price within that range:
- Foundation scope. Slab-on-grade is the least expensive path. Pier and grade-beam systems, required on sloped lots or fill soil, add cost quickly.
- Second-story versus single-story. Going up means structural reinforcement of the existing first floor and more complex roof tie-ins.
- Utility runs. An ADU with its own panel, water service, and sewer lateral costs more than an addition that piggybacks on existing systems.
- Site access. A narrow San Francisco street with no place to stage materials changes the entire logistics budget.
Every job gets a written line-item price before work begins. That’s the Garrison Standard, and we don’t waive it. The price you approve is the price you pay. If the work fails inside one year, the 365-Day Done Right Promise brings us back at no charge. That’s in writing too.
See the difference
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AfterDIY or Call Us?
If your Cover addition or ADU is showing signs of failure, there are things you can check yourself: photograph the crack or stain, measure it, and note whether it changes over a few weeks. Mark the end of a crack with a pencil line and date it. That gives us useful information when we arrive.
What you should not do is attempt structural repairs, open up load-bearing walls, or re-flash a roof intersection yourself. A failed roof tie-in on an addition can mean water has been moving through the framing for months. Open a wall cavity in that condition without understanding load paths and you’re risking a serious injury. Structural framing under load is not a weekend job. Even something that looks simple, like jacking a sagging floor, can shift loads onto members that weren’t designed for them.
If you’re in San Francisco and your addition or ADU is showing symptoms, call us at (831) 610-5598. We’ll come out, take measurements, and give you a straight answer about what’s actually wrong. “Straight number, real scope, no surprises at close-out.”
FAQs
A properly built addition should last the life of the original structure, typically 60 to 100 years for the framing, but the roof tie-in flashing and exterior moisture barriers often need attention at the 15 to 20-year mark due to San Francisco’s fog and salt air. The components that fail first are the intersections: roof-to-wall, wall-to-foundation, and window-to-wall. Call (831) 610-5598 if you’re seeing signs of failure at those points, and we’ll assess what you’re actually dealing with.
Yes, most addition failures are repairable when caught before water damage reaches the structural framing. A failed flashing, a settling pier, or an undersized beam can usually be corrected without demolishing the addition. The window for repair closes as moisture moves deeper into the structure. Call (831) 610-5598 for an honest assessment and a written repair scope.
A detached ADU typically takes 8 to 14 months from permit submittal to final inspection in San Francisco, with permitting alone running 3 to 6 months depending on the neighborhood and scope. Garage conversions run faster, often 4 to 7 months total. We’ll give you a written construction schedule as part of your proposal, not a verbal estimate.
We stock standard structural materials, connection hardware, and finish components from brands we document on every job: KraftMaid, Cambria, and Silestone for interior finishes, James Hardie and Therma-Tru for exterior work, GAF for roofing. Any Cover-specific component is ordered to spec, because structural parts aren’t interchangeable off a shelf. Call (831) 610-5598 and we’ll review your Cover documentation with you.
Get a Written Price for Your San Francisco Addition or ADU
If you own a home in San Francisco and your addition or ADU is showing signs of failure, or you’re planning to build from the ground up, start with a conversation. No pressure, no urgency tactics, no numbers that move at the door. We’ll walk the site, look at your Cover documentation if you have it, and give you a written scope and price. Curtis Lane and the crew answer the phone live, 24/7. Call (831) 610-5598 to schedule your free estimate.
Written by Curtis Lane, Owner, Bradford Remodeling Co – San Francisco, CA at Bradford Remodeling Co San Francisco, serving San Francisco and nearby areas.
