A free site visit, a check of what your lot allows and a written, line-item price.
Get your free estimateADU Company in San Marino, CA
Benson ADU Builders is the ADU and home-addition contractor San Marino homeowners call when they want a written price before any work starts, real timelines, and a 365-Day Done Right Promise stamped on the job. We build accessory dwelling units, home additions, and room additions across San Marino, and we pair access to top prefab brands like Abodu and Dvele with the kind of transparency most people only expect from a rideshare app. If you’re planning an ADU in San Marino, call (903) 568-7222 and we’ll walk you through the numbers before you commit to anything.
Why San Marino Homes Are Different
San Marino isn’t like most of Los Angeles County. The housing stock skews older and more architecturally consistent – a lot of Spanish Colonial and traditional estates on generous, landscaped lots. That matters for ADU work because the existing structures were rarely built with modern utility runs or foundation access in mind. When you’re adding a detached ADU behind a 1930s home, the electrical panel usually needs an upgrade, the sewer line is often clay pipe, and the grading can be trickier than it looks from the street.
The tree canopy is another factor. Mature oaks and deep-rooted ornamentals sit close to many San Marino property lines, which means setback placement and foundation design have to account for root zones. We’ve seen projects where a perfectly good ADU plan shifted six feet because of a protected tree. That’s the kind of on-the-ground reality you won’t see on a generic contractor’s website. It’s also why we write site-specific scopes, not boilerplate bids.
Permitting in San Marino is its own process. The city reviews ADU applications with a level of detail consistent with its design-review standards, so expect a longer plan-check window than some neighboring cities. A setback is the required distance between your structure and the property line, and San Marino enforces these carefully, especially on corner lots. We handle the drawings, submittals, and corrections, so you don’t have to learn the municipal code by accident.
Our Main San Marino Services
The three projects San Marino homeowners ask about most are ADUs, home additions, and room additions. Each has its own dedicated San Marino page because the details, pricing, and local conditions are different enough to warrant it.
ADU Builders in San Marino
An accessory dwelling unit, or ADU, is a fully independent living space on your existing residential lot. In San Marino, detached ADUs are the most popular choice because the lot sizes can support them and homeowners want separation from the main house for tenants, aging parents, or adult children. We build with prefab panels from Abodu and Cover, which cuts on-site framing time significantly compared to traditional site-built methods. Site-built means every wall is framed from raw lumber on your property. Prefab panels arrive cut and assembled in sections, ready to stand. Learn more at ADU Builders in San Marino.
Home Addition Contractor in San Marino
A home addition means expanding the footprint of your existing house, usually a new wing, a larger kitchen, or an attached family room. San Marino homes often have the land for this, but the architectural character matters. The addition has to match rooflines, window styles, and exterior finishes, or it looks grafted on. James Hardie cladding is a common solution because it holds paint well and stands up to the San Gabriel Valley’s summer sun. We spec materials that complement what’s already on your house. Details are at Home Addition Contractor in San Marino.
Room Addition Contractor in San Marino
A room addition is smaller than a home addition, usually a single bedroom, office, or extended living space. In San Marino, many of these projects convert underused side yards or enclosed patios into conditioned living area. The structural work matters even at this scale. Roof tie-ins are critical, and San Marino’s older foundations sometimes need supplemental footings before you can anchor a new room to the house. We handle the engineering, not just the framing. Full scope and pricing on Room Addition Contractor in San Marino.
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 San Marino
Benson ADU Builders is authorized to build with Abodu, Cover, Dvele, and other leading prefab brands, and we install James Hardie cladding on additions across San Marino. Panels and materials are coordinated through our scheduling hub before your project starts, so lead times stay predictable. Visit our brands to research any of these names yourself.
Pricing for ADU Company in San Marino, CA
| Service | Typical range in San Marino |
|---|---|
| Detached ADU (site-built) | $250,000 – $400,000 |
| Prefab ADU (Abodu or Cover) | $180,000 – $320,000 |
| Garage conversion ADU | $120,000 – $200,000 |
| JADU (junior ADU) | $90,000 – $150,000 |
| Home addition (full wing) | $200,000 – $450,000 |
| Kitchen addition | $120,000 – $250,000 |
| Room addition (single room) | $80,000 – $180,000 |
| Primary suite addition | $150,000 – $300,000 |
San Marino prices run on the higher end of these ranges when the project involves a panel upgrade, clay sewer line replacement, or protected-tree setback adjustments. Lower numbers assume a simple lot with modern utilities and no major grading work. Every San Marino project gets a written price before we start, and that number doesn’t change unless you change the scope. That’s The Relay Visibility Guarantee, and it’s not a verbal promise.
Neighborhoods We Serve in San Marino
Benson ADU Builders covers the full city of San Marino, from the estates near Lacy Park to the streets around Huntington Drive and the neighborhoods bordering South Pasadena. Response time for an estimate visit is typically within a few business days, depending on site access and our current schedule.
- Lacy Park area
- Huntington Drive corridor
- San Marino southwest, near the South Pasadena line
- North San Marino, near San Gabriel
Service Area – Cities Near San Marino
We also build in the neighboring communities of San Gabriel, CA, Alhambra, CA, Pasadena, CA, and South Pasadena, CA. Scheduling and dispatch for San Marino jobs are coordinated from the brand’s Los Angeles office, which means our crews are consistently available across the West San Gabriel Valley.
Serving San Marino, CA - Our Local Coverage Area
We’re based in the San Marino 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 San Marino
Yes, we do. We prepare the plans, submit the permit package, and manage corrections through approval. San Marino’s design-review process can add time, but we keep you updated as the application moves. Call (903) 568-7222 for an exact quote on your site.
A prefab ADU takes roughly four to seven months from permit approval to final inspection. Site-built projects usually run six to twelve months. A garage conversion lands on the faster end, around four to six months. Your actual timeline gets written into your contract, not guessed at.
Yes. If your San Marino property has an HOA, a design review board, or both, we prepare the submittal materials they need and attend reviews when required. This is a normal part of the process for us. Call (903) 568-7222 to schedule a free estimate and get your written price.
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 San Marino Customers Say
"Booked a consult online and met the project manager two days later. Weekly progress updates arrived by text with photos. ADU finished on schedule."
- Hannah W."Clean, quiet crew. They respected the neighbors, kept noise to working hours, and swept the driveway every evening."
- Hope C."Communication was the best part. I always knew what was happening that week without having to ask."
- Dolly N.
