A free site visit, a check of what your lot allows and a written, line-item price.
Get your free estimateFast, Reliable ADU Builders Across San Carlos
Building an ADU in San Carlos comes with specific realities: older foundations on flat lots, clay soil that drains slowly, and a planning department that cares about privacy setbacks. We know this because we build here regularly. A detached backyard ADU in San Carlos typically runs $350,000 to $550,000 depending on size, site access, and whether the existing house needs structural or electrical upgrades first. If you want a straight answer on what your lot can support, call us at (707) 760-0502. We’ll walk the property, explain what we see, and give you a written price before anything starts.
Why Lodgewick ADU San Francisco Is San Carlos’s Preferred ADU Builders Company
Lodgewick ADU Builders is the ADU company of the Kingswell family, and every project we take on in San Carlos operates under The Kingswell Guarantee: a written price before work begins, a defined arrival window, a clean job site, and a written guarantee delivered before we drive the first nail. Led by Russ Delmar, our ADU Builders team has worked on detached ADUs, garage conversions, and home additions across the Peninsula, and we treat each San Carlos lot as its own puzzle. Flat rectangular parcels are common here, but so are 90-year-old foundations and 100-amp panels that were never meant to carry a second dwelling.
What San Carlos homeowners care about most, based on the conversations we have every week, is predictability. They’ve been burned by a price that changed at the door or a contractor who vanished after the deposit. That’s why we put every commitment in writing up front. The 365-Day Done Right Promise is the centerpiece: if the work isn’t right, we come back and make it right. No arguing, no invoice. We also answer every call with a live person, 24 hours a day. When you call about your build or your guarantee, you get a human being, not a voicemail tree.
ADU Design in San Carlos
ADU Design in San Carlos is where most projects win or lose money before ground breaks, and the local constraints are real: lot dimensions, privacy setbacks, foundation condition, drainage patterns, and what the planning department will approve on your specific block. In neighborhoods like White Oaks, where many original 1940s cottages sit on unreinforced brick foundations, design work often starts with a structural question rather than an aesthetic one. A full design package, including site analysis, floor plans, structural review, and planning submission support, generally runs $15,000 to $30,000 in San Carlos, with complex lots pushing higher.
Site Constraints Drive the Design
We measure the lot, map the setbacks, and check the soil before drawing anything. On older flat lots with clay soil, drainage has to be designed in from day one, not bolted on after the slab is poured. The same applies to electrical: many San Carlos homes still run on 100-amp panels, so the design must account for a subpanel or a service upgrade.
Privacy and the Planning Review
San Carlos planning looks closely at where windows and doors face when it comes to ADUs on tight lots. We design unit orientation and fenestration to avoid overlooking adjacent yards, and we flag any design-review risk before you pay for final plans. That’s the practical difference between a smooth permit and two extra months of revisions.
Backyard ADU in San Carlos
Backyard ADU construction in San Carlos is where the mid-century ranch stock actually helps: most lots are flat, rectangles, and large enough for a detached unit with its own entrance. The catch is what’s underground. Older homes in White Oaks and around Burton Park sometimes have clay-heavy soil that drains slowly, and any detached structure changes the way water flows across the whole parcel. Costs for a detached backyard ADU in San Carlos typically start around $350,000 for an 800-square-foot studio and run up to $550,000 or more for a two-bedroom unit with upgraded finishes, depending heavily on foundation work, trenching, and site access.
Foundation Work Before Framing
On a flat lot in the White Oaks neighborhood, our crew built a detached ADU behind a 1940s cottage. We first had to seismically retrofit the main house’s unreinforced brick foundation, then upgrade the 100-amp electrical panel and trench a new subpanel to the backyard ADU, adding two weeks and about 15% to the project cost before we even framed. That’s a real example of what building in older parts of San Carlos can involve, and it’s why we scope the foundation before we quote.
Grading and Drainage on an Open Lot
Because San Carlos gets concentrated winter rain, a detached ADU on a bare backyard needs positive drainage away from both the main house and the new slab. We design swales, downspout tie-ins, and sometimes a perimeter drain system, and we include those line items in the written price from the start. If a contractor doesn’t mention drainage on a San Carlos lot, that’s a red flag.
Trusted Brands We Service in San Carlos
We work hands-on with leading ADU systems and materials, including Abodu, Plant Prefab, and James Hardie siding. For San Carlos customers, that means we can match a prefab or panelized system to a mid-century ranch without forcing a design that fights the neighborhood. We also look at the practical side: panel sizes have to clear the fence line, delivery trucks need a realistic path, and the foundation has to meet the manufacturer’s spec. We handle all of that, and we keep product knowledge current so we can tell you honestly whether a particular system makes sense for your lot.
Common ADU Builders Problems We See in San Carlos Homes
- Unreinforced brick foundations in White Oaks. Many 1940s cottages in this neighborhood sit on brick foundations with no steel reinforcement. Building a detached ADU without addressing this can lead to permit rejection or, worse, an unsafe condition on the main house when the new structure changes drainage and loading around it.
- Clay soil and slow drainage on older flat lots. San Carlos soils, particularly in the flatland neighborhoods east of El Camino Real, can hold water longer than homeowners expect. Underestimating trenching, gravel, and drain work is one of the most common budget overruns we fix after another contractor’s quote fell apart.
- Privacy setback conflicts in dense blocks. Lots around Burton Park are wide but shallow in places, and an ADU placed too close to a side or rear fence can fail design review. Neighbors notice windows facing their backs, and San Carlos planning responds to that.
- Undersized electrical panels. Many original 1950s and 1960s homes in the Howard Park and Alder Manor areas still run on 100-amp service. Adding a detached ADU with its own mini-split, oven, and laundry means a panel upgrade or a subpanel, and that should never be a surprise line item.
Pricing for ADU Builders in San Carlos, CA
Detached backyard ADUs in San Carlos generally run $350,000 to $550,000 for a finished unit. Garage conversions and smaller studio ADUs land in the $180,000 to $300,000 range. What moves the number: foundation retrofits on older homes, electrical service upgrades, drainage design, and how difficult the trenching is on your particular lot. We quote every San Carlos project with a written, line-item price before work starts. If the site conditions change once we open things up, we document it and discuss it with you at that moment, no change orders slipped into the final invoice. Call (707) 760-0502 and we’ll schedule a free estimate on your property.
We Also Serve Cities Near San Carlos
Lodgewick ADU Builders in San Carlos also take on projects in the neighboring communities across the Peninsula. We regularly work with homeowners in Millbrae, San Bruno, San Lorenzo, and Daly City, and we bring the same written pricing and guarantee standard to every job, no matter which side of the county line it’s on.
Serving San Carlos, CA - Our Local Coverage Area
We’re based in the San Carlos 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 ADU Builders in San Carlos
Yes, in many cases. White Oaks homes built in the 1940s often rest on unreinforced brick foundations that don’t meet current standards for new construction nearby. We assess the foundation as part of the initial site visit and include any retrofit work in the written price before you commit to anything. Call (707) 760-0502 for a site review.
San Carlos enforces rear and side setbacks that can shrink an ADU’s footprint on shallow lots, and design review pays close attention to window placement. We design units to face away from adjacent yards where possible and submit floor plans that anticipate design-review questions, which saves you revision cycles and months of delay. Estimates are free, so call us to go over your lot’s constraints.
Expect clay-heavy soil in many flatland areas east of El Camino Real, which means slower percolation and more water pooling against slabs after winter rains. We include swales, drainpipe, and sometimes a perimeter French drain in the original quote, not as a change order later. For an exact scope on your property, call (707) 760-0502.
Usually not, unless the panel has already been upgraded to 200 amps. Most original mid-century ranch homes in San Carlos still run on 100-amp service, so a detached ADU with air conditioning and laundry will require either a subpanel on a new circuit or a full panel upgrade. We check this during the free estimate and include it in the written price.
Yes. We work hands-on with Abodu, Plant Prefab, and other established systems, and we coordinate the foundation, utilities, and site prep so the prefab installer has a clean, pad-ready site. We’ll also give you an honest read on whether a prefab route actually saves you money on your specific San Carlos lot, because sometimes it does and sometimes it doesn’t.
If you’re thinking about an ADU on your San Carlos property, start with a conversation. We’ll walk the lot, check the foundation, measure the setbacks, and give you a written price that covers the whole job. Call (707) 760-0502 to schedule your free estimate.
Written by Russ Delmar, Owner at Lodgewick ADU San Francisco, serving San Carlos and the surrounding Peninsula.
