A free site visit, a check of what your lot allows and a written, line-item price.
Get your free estimateADU Company in Brisbane, CA
Most homeowners in Brisbane call us for one of three things: a detached ADU, a home addition, or a room addition. What makes Brisbane work different from anywhere else in San Mateo County is the lot itself. Small parcels, often under 3,500 square feet, with real slopes and fog-heavy summers. That changes foundation design, drainage, and how much sunlight a new structure can actually capture. If you’re weighing any of these projects, we’ll give you a written price before any work starts. Call (831) 272-7212 for a free estimate.
Why Brisbane Homes Are Different
Brisbane’s housing stock tilts toward modest single-story homes built in the 1940s through the 1960s. Many sit on steeply sloping lots that were platted when the expectation was a small house and a small yard, not a second dwelling. That means an ADU in Brisbane frequently becomes a basement conversion or a stacked two-level unit, because the flat, buildable footprint simply isn’t there. The city’s “hillside lot” zoning exemptions differ from South San Francisco’s, which is good news for some projects and a paperwork hurdle for others. We plan around both.
The fog rolls in off the Pacific most summer days, and the wind comes with it. That shapes rooflines, window placement, and exterior material choices more than people expect. Roof runoff needs to handle concentrated winter rain pushing down a slope, so drainage and retention details matter here in ways they don’t on flat lots. And in the Central Brisbane hills, trenching for foundations often hits Franciscan melange rock just a few feet below grade. What starts as a straightforward dig can turn into rock-breaking work that adds cost and time. We tell homeowners this on the first walkthrough, not after the backhoe hits stone.
Our Main Brisbane Services
We handle three kinds of projects in Brisbane, each with its own dedicated page so you can get the full detail on what the work involves and what it costs locally.
Home Addition Contractor in Brisbane
A home addition in Brisbane usually means building up or building into a hillside. The lot rarely allows a simple sideways bump-out. We look at the slope, the setback rules (the required gap between your new structure and the property line), and whether the 1940s-era foundation can carry more load. Soils here often demand deeper footings, and drainage from the new roofline has to be routed with the slope, not against it. Every addition gets a written price first, covered by the 365-Day Done Right Promise. Full detail on the Home Addition Contractor in Brisbane page.
ADU Builders in Brisbane
Brisbane’s hillside-lot rules make detached ADUs here more complex than on the flats south of the city. We spend a lot of time on vertical design: stacked units, built-in storage under stairs, light wells that pull daylight into a hillside lower floor. Detached ADUs in Brisbane commonly run from about $180,000 to $320,000 before site work, and the rock in the Central hills is the biggest wild card. You’ll get a written quote before anything starts, and every technician who comes to your property is background-checked, identity-verified, and photo-badged. That’s the Threshold Standard. More on the ADU Builders in Brisbane page.
Room Addition Contractor in Brisbane
Room additions here often attach to a home built when bedrooms were smaller and closets were a luxury. The job might be a primary-bedroom bump-out, a family room over a garage, or a daylight basement finished into livable square footage. Brisbane’s slope means drainage and retaining walls get as much attention as framing. We handle the permit drawings, the foundation work, and the finish work under one written contract. One crew, one name on the paperwork, one price. Details on the Room Addition Contractor in Brisbane page.
What happens when you call
- 1
A real person answersNo phone trees - you reach a local pro.
- 2
You get an upfront price rangeHonest numbers before anyone is dispatched.
- 3
A background-checked tech heads outLicensed & insured, dispatched right away.
- 4
You approve before work beginsNothing starts until you say go.
Brands We Service in Brisbane
We have working experience with our brands including Plant Prefab, Tuff Shed, James Hardie, and Abodu. On Brisbane hillsides, we order parts at project start so the slope-specific components arrive before the trenching crew wraps up, not after.
Pricing for ADU Company in Brisbane, CA
| Service | Typical range in Brisbane |
|---|---|
| Detached ADU (400 – 800 sq ft) | $180,000 – $320,000 before site work |
| Garage conversion ADU | $120,000 – $190,000 |
| Attached ADU / interior conversion | $90,000 – $160,000 |
| Basement conversion ADU | $150,000 – $260,000 |
| Home addition (200 – 400 sq ft) | $120,000 – $220,000 |
| Home addition (400 – 800 sq ft) | $180,000 – $320,000 |
| Room addition (single room) | $60,000 – $110,000 |
| Second-story addition over garage | $140,000 – $250,000 |
| Site work / foundation (sloped lots) | $25,000 – $65,000 |
| Architectural and permit drawings | $6,000 – $15,000 |
| Soils report and geotech review | $3,500 – $8,000 |
| Drainage and retaining wall work | $12,000 – $40,000 |
What pushes cost up in Brisbane faster than anything else is Franciscan melange rock during excavation, plus retaining-wall work on steep lots. The written price you get before we start already accounts for the slope, the drainage, and the rock conditions we can see. If something changes in the field, we stop and show you the numbers before any new work goes forward.
Neighborhoods We Serve in Brisbane
We work across Brisbane’s small, distinct pockets, from the flat streets by the old rail line up into the Central hills and the neighborhoods near Visitacion Avenue. Most of our crews can reach a site within a normal scheduling window a few days out, since we keep local Brisbane crews on rotation rather than dispatching from across the Bay.
- Central Brisbane hills
- Brisbane Village
- Visitacion Avenue area
- Crockers Ridge
- Brisbane lagoon area
Service Area – Cities Near Brisbane
We also work regularly in South San Francisco, CA, where flat lots make trenching faster; Pacifica, CA, where the coastal wind demands tighter cladding details; San Francisco, CA for interior conversions and garage ADUs under stricter planning conditions; and San Mateo, CA for larger lot additions with fewer slope constraints.
Serving Brisbane, CA - Our Local Coverage Area
We’re based in the Brisbane 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 Company in Brisbane
Yes. We prepare and submit the permit drawings, coordinate with the Brisbane planning and building departments, and respond to plan-check comments. You don’t have to learn the hillside-lot exemption paperwork. The permit process in Brisbane usually takes longer on sloped lots because of the geotech review. Call (831) 272-7212 and we’ll tell you what your specific lot will require.
It can, if the contractor doesn’t test for it. We recommend a soils report and sometimes a test pit during the quote phase on any Brisbane hillside site. That way the excavation cost is in your written price before we start trenching, not a surprise after the backhoe hits melange rock.
Most detached ADUs in Brisbane take 8 to 14 months from permit submission to final inspection. Sloped lots with retaining work and rock excavation run longer than flat-lot garage conversions. We’ll give you a schedule in writing as part of your estimate. Call (831) 272-7212 to set up a walkthrough.
Ready to talk through your project? Call (831) 272-7212 and we’ll schedule a free on-site estimate in Brisbane. Written price first, no surprises after.
What happens when you call
- 1A real person answersNo phone trees - talk to a local adu pro.
- 2You get an upfront price rangeHonest numbers before anyone is dispatched. No surprises.
- 3We come out and measureLicensed & insured, at a time that suits you - the visit and the quote are both free.
- 4You get the price in writingLine-itemed, yours to keep, and nothing starts until you say go.
What Brisbane Customers Say
"Every crew member was vetted and carried a badge, which matters when they are around your family for months. Tidy site every day."
- Daniel F."Insulated the walls and ceiling properly. It stays comfortable even in July."
- Tamika W."They handled the drawings and the permit paperwork for us. All I had to do was pick the finishes."
- Rosa M.
