An ADU Built for the Tiburon Peninsula, Not a Flat Suburban Lot
Adding an accessory dwelling unit in Tiburon is rarely as simple as dropping a prefab box on a back corner. The peninsula juts into the Bay with water on three sides, so most properties sit on a slope, a ridgeline, or a tight waterfront parcel where every foot of grade and every view corridor matters. Whether your home is a 1950s and 60s post-and-beam in Paradise Cay, a wood-joinery modern in the Callister tradition, a Mediterranean villa in the Tiburon uplands, or a contemporary glass-walled house in Hill Haven, an ADU here has to read as a deliberate extension of the main residence, not an afterthought bolted onto the back.
New Key Construction is a Marin design-build firm that handles interior design and construction under one roof. For your ADU that means one team carries the project from first site walk to final walkthrough: priced options up front, photoreal 3D renderings before any permit is pulled, and white-glove project management so you are not refereeing between an architect, a separate contractor, and the Town of Tiburon. You see the finished unit, sited on your actual lot and matched to your actual house, before a single dollar goes into the ground.
How an ADU Works on a Tiburon Slope
Most Tiburon parcels do not give you the easy footprint that ADU rules assume. We start with a real survey of grade, drainage, and the existing structure, then design to the conditions in front of us: a downslope unit tucked under a view deck, a garage conversion that keeps the street face intact, or a detached studio terraced into the hillside so it never blocks the neighbor's sightline to the Bay or the city skyline. On a peninsula where homeowners buy for the water view, protecting those sightlines is not a courtesy, it is often what gets a project approved.
Because we design and build, the structural reality and the design intent stay in the same hands. The framing strategy for a hillside foundation, the retaining work, the way a roofline steps with the slope: all of it is resolved before we present, so the renderings you approve are buildable and the price behind them is real. You get fixed, priced options instead of an open-ended estimate that drifts upward once excavation begins.
Design, Renderings, and Permits Under One Roof
Tiburon and neighboring Belvedere take exterior design seriously. Almost all exterior changes go through Design Review with the Town of Tiburon, even work that would not otherwise need a building permit, and the Design Review Board weighs how a new structure sits in its setting, how it affects neighboring views, and how it reads from the street and the water. State ADU law sets the baseline (commonly an 850 square foot one-bedroom or 1,000 square feet for two bedrooms, a 16-foot height ceiling, and a four-foot side and rear setback for a new detached unit), but in Tiburon how you meet those numbers is what carries the application.
We build for that review from day one. Our photoreal 3D renderings show massing, materials, and rooflines in context, which is exactly the language Design Review responds to, and we coordinate with Marin County environmental health where a parcel is on septic rather than sewer. Anything larger than the by-right envelope goes through discretionary Design Review, and we plan that path with you up front rather than discovering it mid-permit. One team, one set of drawings, one point of accountability through Town hall and into construction.
What You Can Build
Tiburon homeowners use ADUs for multigenerational living, a private guest suite for visitors who come for the sailing and the views, a quiet home office detached from the main house, or long-term rental income on one of Marin's most sought-after addresses. We deliver detached studios and one-bedroom units, garage and lower-level conversions, attached additions, and junior ADUs carved from existing square footage. The interior design is part of the same engagement, so the cabinetry, finishes, and lighting in the ADU carry the same level as the main home rather than feeling like a downgrade out back.
Frequently Asked Questions
Do I need Design Review for an ADU in Tiburon?
In most cases, yes. The Town of Tiburon routes nearly all exterior changes through its Design Review process, and a detached or visible ADU almost always qualifies. The board looks closely at massing, materials, and protected views on this view-driven peninsula, which is why we present photoreal 3D renderings in context before the application goes in.
How big can my Tiburon ADU be?
Under current state ADU rules the common by-right sizes are up to 850 square feet for a one-bedroom unit and up to 1,000 square feet for a two-bedroom, with a 16-foot height limit and a four-foot side and rear setback for a new detached structure. Larger or taller units are possible but move into discretionary Design Review. We confirm your exact envelope against your parcel before designing.
Can you build an ADU on a steep Tiburon hillside lot?
Yes, and it is most of what we do here. Hillside and waterfront parcels need careful foundation, retaining, and drainage work, which is exactly why a single design-build team is an advantage: the structural solution and the design are resolved together before you approve anything. We site the unit to preserve your views and your neighbors' sightlines.
How does pricing work?
We give you fixed, priced options up front rather than a loose estimate. Because we design and build, the number behind each rendering reflects the real foundation, framing, and finish work your lot requires, so you are choosing between clear options instead of watching costs climb after excavation starts.
Will the ADU match my existing home?
That is the point of design-build. We design the ADU as a deliberate extension of your main residence, whether that is a mid-century post-and-beam, a wood-joinery modern, a Mediterranean villa, or a contemporary glass-walled house, and our interior design team carries the finishes through so the unit feels like part of the property, not a separate project.
Ready to add an ADU that fits your Tiburon lot and your home? Contact New Key Construction for a site walk and priced options, and see your unit in photoreal 3D before any permit is pulled.
