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 Bruno
Building an accessory dwelling unit (ADU) – a separate living space on your existing property – in San Bruno means navigating rules that don’t apply in Daly City or Millbrae. The Mills Park and Crystal Springs neighborhoods carry a historic prohibition on new detached ADUs, while hillside lots near Skyline Boulevard trigger septic setbacks and drainage reviews that flatland projects never face. Our team knows these streets, these lots, and the San Bruno planning desk. If you’re weighing a garage conversion, a junior ADU (a smaller unit built within the existing home’s footprint), or a detached unit, call (707) 760-0502 for a written estimate before you spend a dollar on plans.
Key Takeaways for San Bruno Homeowners
- Detached ADUs in San Bruno typically run $180,000 to $380,000 depending on lot slope, septic status, and architectural matching requirements.
- Mills Park and Crystal Springs prohibit new detached ADUs entirely – garage conversions and junior ADUs remain your options there.
- Homes built from the 1940s to 1970s on 5,000-7,000 sq ft lots often need electrical service upgrades before an ADU can pass inspection.
- We provide a written price before any work starts, and a written 365-Day Done Right Promise on every project.
Why Lodgewick ADU San Francisco Is San Bruno’s Preferred ADU Builders Company
Russ Delmar leads our San Bruno projects, and he’s walked enough of these lots to know what the planning department will flag before you submit anything. San Bruno’s review process is stricter than most Peninsula cities, especially around architectural matching – your ADU has to look like it belongs with the existing house, not just meet a height limit. That’s where our ADU Builders team earns its keep. We scope the design to pass review the first time, not the third.
Every Lodgewick project operates under The Kingswell Guarantee. That means a written price before work begins, a defined arrival window, a clean job site, and a written guarantee on every build. If something isn’t right within 365 days, we come back and make it right – free. San Bruno homeowners call us because they’ve been burned by a price that changed at the door or a crew that vanished after the concrete was poured. We put everything in writing. A live person answers our phone 24/7, so when you call about your build at 8pm, you get Russ or a member of the crew, not a voicemail loop.
ADU Plans in San Bruno
ADU Plans in San Bruno are not a formality – they’re the difference between a permit issued in 6 weeks and a rejection letter that costs you months. San Bruno requires architectural matching: your ADU’s roofline, window style, and exterior materials must reflect the main house. On a 1960s ranch off Sneath Lane, that means horizontal siding and low-pitch roofing, not a modern box. We prepare site plans, floor plans, structural drawings, and energy calculations that account for San Bruno’s specific design standards before submission. A full permit-ready plan set in San Bruno runs $4,500 to $9,500 depending on whether you need structural engineering for a hillside foundation or Title 24 energy documentation for a two-story unit.
Hillside & Septic Site Verification
On any San Bruno lot above Junipero Serra Boulevard or near the Crystal Springs watershed, we verify sewer versus septic before drawing a single wall. Septic leach field setbacks can force a detached ADU into a different corner of the lot, or eliminate it entirely in favor of an attached unit or garage conversion. We’ll pull your property’s sewer lateral records and, where needed, bring in a civil engineer to locate field lines. That cost gets folded into the plan set, not sprung on you later.
Design Review Coordination
San Bruno’s design review isn’t a rubber stamp. We attend the review with you, respond to planner comments in writing, and revise drawings until the city signs off. Our familiarity with San Bruno’s residential design guidelines means we know what a reviewer will question on a 1950s rancher versus a 1980s two-story near Rollingwood. Plan revisions after a review comment cost $500 to $1,800 depending on scope – we give you that range before the first submission.
ADU Contractor in San Bruno
An ADU Contractor in San Bruno has to do more than frame walls and pull wire. Your contractor has to coordinate with the city’s building inspector on foundation depth for hillside lots, manage drainage and retaining-wall conditions that San Bruno’s steep terrain demands, and upgrade electrical panels on homes built when 100 amps was plenty. We handle the full build: excavation, foundation, framing, roofing, plumbing, electrical, drywall, and finish work. Turnkey construction on a detached ADU in San Bruno runs $180,000 to $380,000 depending on size, slope, and whether you choose site-built framing or a prefab system from Plant Prefab or Boxabl. A garage conversion runs $95,000 to $180,000; a junior ADU inside the existing home runs $70,000 to $130,000.
Foundation & Drainage on Sloped Lots
Many San Bruno lots slope toward the Bay or toward San Bruno Mountain. That means stepped footings, retaining walls, and drainage swales that flatland contractors never think about. On a hillside lot off Skyline Boulevard near Crystal Springs, we recently coordinated a two-story detached ADU on a 1955 rancher with an outbuilding foundation too close to a septic leach field. Before framing, we had a civil engineer verify field lines, upgraded the original 100-amp panel, and re-routed the ADU feeder. The city’s design review approved because the ADU matched the home’s mid-century ranch features. That’s the kind of sequencing you only get right by doing it here, repeatedly.
Service Upgrades & Utility Coordination
Homes built in San Bruno from the 1940s through the 1970s often have original foundations and electrical systems. An ADU adds load – a second kitchen, a water heater, laundry, maybe EV charging. We scope the panel upgrade at the plan stage, so the price you see includes the service change. If PG&E needs to run a new drop or the city requires a sewer lateral replacement, we flag it before you sign anything. No change orders at the door.
Trusted Brands We Service in San Bruno
We work with the prefab and materials systems that make sense on San Bruno lots. For tight hillside lots where a crane can’t reach, Boxabl’s foldable modules handle access challenges well. For larger flats near Crestmoor, Plant Prefab’s panelized systems speed up framing without sacrificing the architectural matching San Bruno requires. We also use James Hardie siding extensively because it holds up to the fog and damp that roll in off the Pacific – standard wood lap rots faster here than homeowners expect. We keep common components staged for San Bruno jobs, which shortens lead times compared to contractors ordering everything from out of state.
Common ADU Builders Problems We See in San Bruno Homes
- Permit rejection for Mills Park or Crystal Springs detached units: San Bruno prohibits new detached ADUs in these neighborhoods. A contractor who doesn’t check the zoning map before drawing plans costs you design fees and months of waiting. We verify zoning first, always.
- Septic surprise after the quote: Some San Bruno lots, especially east of El Camino Real toward the hills, are on septic rather than sewer. Leach field setbacks can force a redesign from detached to attached, or kill the project. We confirm sewer vs. septic before quoting a detached unit.
- Electrical panel failures on 1940s-1970s homes: San Bruno’s older housing stock frequently has 100-amp panels that can’t carry an ADU load. Upgrading to 200 amps mid-project is expensive and delays inspection. We scope it in the plan set.
- Fog and moisture damage on exterior materials: San Bruno’s cool, damp summers mean untreated wood siding and unsealed flashing fail within a few years. We specify moisture-resistant materials – James Hardie siding, proper WRB, and flashing details – from day one.
Pricing for ADU Builders in San Bruno, CA
A turnkey detached ADU in San Bruno runs $180,000 to $380,000. The swing comes down to three things: lot slope, sewer versus septic, and whether you need a two-story unit to fit the buildable area. Garage conversions run $95,000 to $180,000. Junior ADUs inside the existing home run $70,000 to $130,000. Plan sets run $4,500 to $9,500 before construction. Hillside lots trigger retaining walls, stepped footings, and drainage work that add $15,000 to $45,000 depending on the grade. We give you a written, line-item price before any work starts – not an estimate that drifts upward. Call (707) 760-0502 for a free estimate on your San Bruno lot.
We Also Serve Cities Near San Bruno
Our crews work throughout the northern Peninsula, including San Bruno, Millbrae, Daly City, San Francisco, and San Carlos. If you’re just across the border and wondering whether your lot has similar zoning quirks, call us – the rules change from one city to the next, and we know where they differ.
Serving San Bruno, CA - Our Local Coverage Area
We’re based in the San Bruno 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 Bruno
No. Mills Park and Crystal Springs carry a historic prohibition on new detached ADUs. You may still pursue a garage conversion or a junior ADU within the existing home’s footprint, but a free-standing unit on the lot won’t get a permit. Call (707) 760-0502 and we’ll check your specific parcel before you spend anything on design.
San Bruno requires architectural matching: your ADU’s roofline, window proportions, and exterior materials must reflect the existing home. South San Francisco and Millbrae have more flexible standards. In San Bruno, a mid-century rancher needs an ADU that reads as mid-century ranch, not a modern cube bolted on. We handle the design review coordination so the match passes the first submission.
If your property is on septic, the leach field creates a setback buffer that a detached ADU cannot cross. We confirm sewer versus septic and, where needed, bring in a civil engineer to locate field lines before we draw plans. On some lots this forces an attached ADU or garage conversion instead. We’ll tell you early, not after you’ve paid for a detached design.
Sloped lots require stepped footings, retaining walls, and drainage swales that flatland builds skip entirely. Excavation takes longer, materials staging is harder, and the city’s grading review adds conditions. Plan on $15,000 to $45,000 in additional site work on a steep San Bruno lot compared to a flat one. We scope the slope before we quote, so the price you get is the price you pay.
Yes, with conditions. San Bruno’s architectural matching requirement means the prefab unit’s exterior has to be modified to match your home – Abodu and Mighty Buildings both allow custom exterior finishes. Boxabl works well on tight hillside access where a standard module can’t be delivered. We’ll match the system to your lot, budget, and the city’s design standards.
Written by Russ Delmar, Owner at Lodgewick ADU San Francisco, serving San Bruno since 2010.
