Detached ADUs, garage conversions, JADUs, and second-story additions — SDW Construction designs and builds accessory dwelling units across San Francisco, Oakland, San Jose, Marin County, and the entire Bay Area. Licensed, insured, and local since 2001.
An accessory dwelling unit is one of the most effective investments a Bay Area homeowner can make. A well-built ADU adds a rental income stream in one of the country’s highest-rent markets, increases your property’s resale value, and gives your family flexible space — whether that’s housing an aging parent, a returning adult child, or a long-term tenant who helps cover your mortgage.
SDW Construction has been building structures across the San Francisco Bay Area since 2001. We handle ADU projects from the ground up — site assessment, structural foundation work, concrete flatwork, framing, and coordination through the full construction process. We work across San Francisco, Oakland, Berkeley, San Jose, Fremont, Marin County, the Peninsula, and East Bay communities, and we understand the permit landscape, soil conditions, and setback rules that vary block by block in this region.
Ready to find out what's possible on your property? Request a free onsite ADU assessment → or call us at (510) 426-1854. We visit your site, review your lot, and give you an honest assessment of what you can build.
Explore some of our recently completed Accessory Dwelling Unit (ADU) projects across the San Francisco Bay Area. Each project reflects our commitment to quality construction, thoughtful design, and efficient project management. From detached backyard ADUs to garage conversions and custom-built units, our team delivers durable structures that add real value and usable living space to every property.
We work closely with homeowners throughout San Jose, Oakland, Fremont, Berkeley, and surrounding Bay Area communities to design and build ADUs that meet local building codes while maximizing functionality and long-term property value.
Bay Area lots come in every shape and configuration — narrow urban parcels in San Francisco’s Mission District, flat suburban yards in San Jose and Fremont, sloped hillside lots in Oakland and Marin. The right ADU type depends on your lot, your budget, your existing structure, and what your local building department allows. Here are the four main types we build.
A fully standalone dwelling unit built in your backyard — its own foundation, framing, roof, and utility connections. Detached ADUs offer the most flexibility in size, layout, and rental use. California law now allows detached ADUs on most single-family and multi-family lots, with streamlined permitting in most Bay Area cities. Maximum size in most jurisdictions is 1,200 sq ft or up to 50% of the primary dwelling, whichever is smaller.
Most Popular
Converting an existing attached or detached garage into a livable dwelling unit. Garage conversions make use of an existing structure and existing foundation, which often reduces both construction cost and construction timeline compared to a new detached build. In San Francisco and Oakland, garage conversion ADUs are one of the most common ADU types because of limited rear yard space and the abundance of older homes with underutilized garages.
Cost-Effective
An ADU built as an addition to the primary residence — sharing at least one wall with the main home. Attached ADUs are common on lots where the rear yard is too small for a detached structure, or where the homeowner wants to maximize square footage while keeping a connected footprint. They require the same structural framing and foundation work as a detached ADU, but connect into the existing building envelope.
Space-Efficient
A Junior ADU is a smaller unit — maximum 500 sq ft — created entirely within the footprint of an existing single-family home, often from a bedroom, basement, or ground-floor space. JADUs require an owner-occupancy condition in most Bay Area jurisdictions and must include an efficiency kitchen, but they can be created with relatively minimal construction compared to a full ADU. Ideal for homeowners who want rental income but don't have the budget or lot space for a full build.
Minimal Disruption
A full living unit built above an existing garage, creating a second-story addition that doesn't consume any yard space. Above-garage ADUs require careful structural assessment of the existing garage foundation and framing to confirm it can carry the added load — or a new structural system designed around the existing garage footprint. Common in Peninsula cities, San Jose, and East Bay suburbs where yard space is limited but the garage structure is large and solid.
No Yard Impact
Factory-built ADU units delivered to your property and set on a prepared foundation. SDW Construction prepares the site — grading, foundation, utilities, and concrete flatwork — for prefab and modular ADU units. Site preparation is one of the most technically demanding parts of a prefab ADU project, and it requires the same licensed contractor expertise as a traditional build. We work with Bay Area prefab ADU manufacturers and can coordinate the full site prep scope.
Fastest Timeline
ADU construction requires multiple scopes working together — foundation, concrete flatwork, structural framing, and coordination with your utility and finish trades. Here’s the scope SDW Construction covers on a typical Bay Area ADU project.
The Bay Area’s soil, seismic environment, and terrain create construction challenges that a contractor from outside the region will consistently underestimate. Every ADU we build is designed for the actual conditions on that specific lot — not a generic plan dropped on a Bay Area property.
Expansive Clay Soils — East Bay & South Bay
Large parts of Oakland, Berkeley, Fremont, Hayward, and San Jose sit on expansive Montmorillonite clay soils that swell significantly when wet and shrink when dry. This seasonal movement is the leading cause of foundation cracking, slab settlement, and concrete damage on Bay Area ADU projects. Our approach for clay soil sites: deeper excavation to competent soil, properly compacted aggregate base (sometimes 5–6 inches instead of the standard 4), and foundation design that accounts for seasonal movement rather than fights it.
Seismic Design Category D — Every Bay Area ADU
Every ADU built in the San Francisco Bay Area falls under California’s Seismic Design Category D — one of the most demanding residential seismic classifications in the country. This means your ADU’s framing must include a fully engineered shear wall system with structural sheathing, specified nailing schedules, and hold-down hardware anchored to the foundation. An ADU framed without proper shear walls will fail inspection and will perform poorly in an actual earthquake. We install shear walls to the structural engineer’s schedule on every project, every time.
Hillside Lots — Oakland Hills, Marin, San Francisco
Many of the Bay Area’s most desirable ADU sites are on hillside lots — in the Oakland Hills, Marin’s Tam Valley, Tiburon, and Mill Valley, and San Francisco’s Bernal Heights, Twin Peaks, and Glen Park neighborhoods. Hillside ADU sites often require retaining walls to create a level building pad, concrete pumping for foundation pours on restricted-access slopes, and drainage systems designed for the Bay Area’s concentrated winter rainfall. SDW Construction has in-house shotcrete capability for hillside retaining walls and concrete pumping for difficult access pours.
Impervious Surface & Stormwater Rules
Several Bay Area jurisdictions — particularly Marin County cities and parts of the East Bay — enforce stormwater management ordinances that limit how much of a lot can be covered by impervious surfaces like concrete, pavers, and roofing. Adding an ADU foundation and a connecting concrete path or driveway may push your lot over the impervious coverage limit in sensitive jurisdictions. We assess your lot’s current coverage at the site visit so you know before any plans are drawn.
Every ADU project follows a clear sequence. Here’s what to expect when SDW Construction handles the structural work on your Bay Area ADU.
Pre-Construction
We visit your property, measure the lot, evaluate soil conditions, drainage, and access, review your local jurisdiction's ADU rules, and confirm what can realistically be built within your setbacks and coverage limits. You get an honest assessment — not a sales pitch — and a written scope of what SDW Construction would handle on your project.
Planning
We work with your architect or ADU designer to review structural drawings, flag any site conditions that need to be addressed in the plans, and confirm the foundation and framing scope. We help you understand what's required for permit submittal in your city and assist with permit coordination — we've navigated SF DBI, Oakland, San Jose, Marin, and Peninsula building departments for over 20 years.
Site Prep
We excavate to the correct depth for your foundation type, remove all organic material and unsuitable soil, grade the building pad to proper drainage slope, and install any required drainage systems — channel drains, French drains, or perimeter drainage — before any concrete is placed. Bay Area clay soils and concentrated winter rainfall make this step critical to long-term performance.
Foundation
We place all foundation formwork, rebar, and anchor bolts per the structural engineer's drawings, coordinate the foundation inspection, and pour. Foundation anchor bolt locations are verified against the framing plan before the pour — far easier to correct at this stage than after the concrete has set. Exterior concrete flatwork — paths, patios, and driveway approaches connected to the ADU — are poured to the correct slope and with integrated drainage.
Framing
Floor system, wall framing, shear wall sheathing and hardware, roof framing — all installed by our own trained crew to the structural engineer's drawings. We verify anchor bolt locations, install all hold-down hardware from the shear wall schedule, and nail every shear wall panel to the specified pattern. We don't call for the rough framing inspection until every connector is in place and the framing package matches the structural drawings.
Inspections
We coordinate all required structural inspections — foundation, rough framing, and any special inspections required by your jurisdiction — and pass them on the first attempt. Once structural work is complete and inspections are signed off, we provide a clean handoff to your finish trades — electrician, plumber, HVAC, insulation, and drywall — with all rough framing blocking and penetrations in place.
Pour Day
We order a ready-mix concrete — typically 4,000 PSI with a 4–5 inch slump. The crew screeds, bull-floats, and hand-finishes before the concrete sets. Decorative finishes like stamping or exposed aggregate are applied at this stage.
The Bay Area has seen a surge in ADU contractors since state law streamlined approvals. Not all of them have the structural experience, local knowledge, or licensing to handle the full scope of an ADU project in California’s seismic environment. Here’s what matters when you’re evaluating contractors.
| What to Ask | Why It Matters | SDW Construction |
|---|---|---|
| Are you CSLB licensed? | Unlicensed contractors cannot pull permits. If they pull under your homeowner permit, you carry all liability. | Yes — Class B General Building Contractor |
| Do you carry workers’ comp? | Without workers’ comp, you are liable if a worker is injured on your property. | Yes — certificates provided before work begins |
| Do you understand Bay Area seismic requirements? | Shear wall errors are the most common framing inspection failure in California. SDC D is not optional. | 20+ years framing to California SDC D requirements |
| Do you use your own crew? | Subcontracted crews have no accountability to you or your schedule — and the GC won’t be on site. | Our own trained crew on site every day |
| Do you provide written estimates? | Verbal estimates leave you with no protection when costs change mid-project. | Detailed written estimate before any work begins |
| Do you have Bay Area permit experience? | SF DBI, Oakland, San Jose, and Marin all have specific ADU requirements. A contractor unfamiliar with them will cause delays. | 20+ years working with Bay Area building departments |
SDW Construction has been building structures across the Bay Area since 2001 — as SDW Construction and S.D. White Construction. We’ve poured foundations, framed ADUs, and worked through the permit processes in San Francisco, Oakland, San Jose, Berkeley, Marin, and Peninsula cities long before ADUs became the construction trend they are today. We’re not a company that pivoted to ADUs when the state made them easier to permit. We’re a structural contractor that has always done this work.
Ready to upgrade your driveway? Tell us about your project and we’ll schedule a free onsite visit — no pressure, no obligation. Serving the Bay Area since 2001.
Free onsite ADU assessment — we visit your property, evaluate your lot, and give you an honest picture of what’s possible before you spend a dollar on plans. Licensed, insured, and local since 2001.
Quick answers to questions you may have. Can’t find what you’re looking for? Check out our full documentation.
California state law now allows ADUs on virtually all single-family and multi-family residential lots across the Bay Area. Most properties that previously couldn’t build an ADU due to lot size, setbacks, or parking requirements are now eligible under state law. The best way to confirm what’s possible on your specific lot is a free onsite assessment — lot dimensions, existing structures, soil conditions, and local setback rules all affect what can be built and where.
A typical detached ADU in the Bay Area takes 12–18 months from start to certificate of occupancy — including permitting, design, and construction. The permitting phase alone (from plan submittal to permit issuance) typically takes 3–6 months in most Bay Area cities. Construction of the structural scope — foundation, framing, and exterior — typically takes 3–5 months depending on site conditions and project size. Finish work adds additional time. Oakland currently has some of the fastest ADU permit timelines in the Bay Area. San Francisco’s DBI is typically slower due to plan check volume.
Most Bay Area cities require stamped architectural and structural drawings for ADU permit applications. Some cities — Oakland, San Jose, and others — offer pre-approved ADU plan sets that can reduce or eliminate the custom design requirement for standard ADU types. If you use a pre-approved plan, you still need a licensed contractor to build it. If your ADU has a non-standard footprint, hillside site, or complex structural requirements, you will need a licensed architect and structural engineer to prepare the plans.
A JADU (Junior ADU) is a smaller unit — maximum 500 sq ft — created entirely within the footprint of your existing home. It must include an efficiency kitchen but can share a bathroom with the main house. JADUs require an owner-occupancy condition in most Bay Area jurisdictions. A standard ADU can be detached, attached, or a garage conversion, has a maximum size of 1,200 sq ft in most Bay Area cities, and includes its own complete kitchen and bathroom. Both ADUs and JADUs are allowed on the same lot simultaneously in most California jurisdictions.
Under California state law (AB 670, effective 2020), HOA CC&Rs that prohibit or effectively prohibit ADU construction are unenforceable. Your HOA cannot deny your right to build an ADU that complies with local zoning. However, your HOA may still enforce reasonable design and architectural standards — exterior finishes, rooflines, and colors may need to comply with HOA guidelines. Check your CC&Rs and confirm with your local building department before submitting plans.
S.D. White Construction handles the structural scope — foundation, concrete flatwork, structural framing, shear walls, and permit coordination. For finish trades (electrical, plumbing, HVAC, insulation, drywall, flooring, and fixtures), we work alongside your chosen finish contractors or can refer you to trusted Bay Area trade contractors we’ve worked with on previous projects. We can also coordinate the full project as the general contractor if you’d prefer a single point of contact throughout the entire build.
We are a licensed and insured Bay Area concrete contractor providing all types of concrete construction for both commercial and residential clients. Operating as SDW Construction / S.D. White Construction, serving the Bay Area since 2001.
630 Second St rodeo CA 94572
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Saturday: Closed
Sunday: Closed
Proudly serving the entire San Francisco Bay Area — San Francisco, Oakland, San Jose, Marin County, the Peninsula, and surrounding cities.
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