Free written scope consultation - allowances, timeline, and change-order rules on paper before a single trade is scheduled
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AfterFast, Reliable Home Additions & ADU Across Tiburon
Home additions and ADU construction in Tiburon run $45,000-$130,000 for a room addition and $90,000-$220,000 for a new detached ADU, with garage conversions landing between $30,000 and $80,000. The real question isn’t the starting number. It’s whether the contractor quoting it understands what opening up a 1960s hillside home in Tiburon actually turns up: salt-corroded hardware, undersized beams, and a design review board that cares as much about your neighbor’s view as your square footage. Our Home Additions & ADU crews have worked these hills long enough to know what’s behind the stucco before we open it. Call (877) 610-1318 and we’ll walk the site with you before you spend a dollar.
Why Barrett & Sons Construction Is Tiburon’s Preferred Home Additions & ADU Company
We’ve been at this since 1998, and Tom Barrett still answers his own phone. That matters in Tiburon, where the difference between a good addition and a stalled one is often a contractor who knows the Town’s design review process and the neighbors who participate in it. Our crews are Tom’s sons and their teams, not subcontractors dispatched from an out-of-state call center. When you call about a second-story addition on a hillside lot above Paradise Drive, the person you speak with knows exactly where that is.
Tiburon homeowners call us because we write every scope, allowance, and price change on paper before work starts. That’s not corporate policy. It’s how Tom has run jobs for over 29 years, and it’s why our 90-Day Done Right Promise is printed on every contract. If something isn’t right, one call brings Tom back. No voicemail maze, no waiting on a district manager.
The permit inspector works for you, not for me. That’s why we like him. Every eligible job in Tiburon gets permits pulled and inspections signed. We don’t tell you permits are optional. We tell you what the Town will require, and we schedule for it from day one.
Our Home Additions & ADU Services in Tiburon
ADU Design & Permitting
A new detached ADU in Tiburon means navigating Marin County’s hillside setbacks, the Town’s view-protection ordinance, and often a geotechnical review before plans are even stamped. We handle the full design and permitting path, including story-pole installation and neighbor outreach. Most Tiburon ADU applications take months, not weeks, and we set that expectation on day one rather than letting you discover it at a Planning Commission meeting.
Garage Conversion ADU
Converting an attached garage in Tiburon runs $30,000-$80,000 and is usually the fastest path to a rentable unit, because it doesn’t add a new footprint. But many Tiburon garages from the 1960s and 70s sit on slabs with no moisture barrier, and the salt-laden air that comes off the Bay on three sides has often done quiet damage to sill plates and door hardware. We inspect before we quote, and we put what we find in the contract.
New Detached ADU
Detached ADUs on Tiburon’s hillside lots require engineered caisson or grade-beam foundations in almost every case. The slope that gives you a bay view also makes the ground less stable, and the Town won’t sign off on a foundation that wasn’t designed for it. We’ve built enough of these to know what the geotech will say before they say it. Plan on $90,000-$220,000 for a complete detached unit with utilities, from first stake to final inspection.
Junior ADU & Interior Conversion
A junior ADU carved out of an existing Tiburon home is often the most cost-effective way to add a rental unit or extended-family space, because you’re working within walls that already exist. The catch is that opening those walls in a 1968 post-and-pier house frequently reveals what decades of salt air did to the framing. We budget for it in writing, so the discovery doesn’t become an argument.
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.
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A background-checked tech heads outLicensed & insured, dispatched right away.
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You approve before work beginsNothing starts until you say go.
Trusted Brands We Service in Tiburon
We install materials you can look up, not mystery brands off a van. On Tiburon addition and ADU jobs, we use Schluter for waterproofing systems in wet areas, where the marine air makes a bad flashing job fail fast, and GAF for any roofing integration where the new second story ties into the existing roof. We also stock the fasteners, flashing, and hardware these systems require so a Tiburon job doesn’t stall waiting on a part from a warehouse three states away.
Common Home Additions & ADU Problems We See in Tiburon Homes
- Salt-corroded structural hardware and flashing. Tiburon is nearly surrounded by San Francisco Bay, so marine air hits homes from multiple compass directions at once. Hardware that would last 40 years in Corte Madera fails in a decade here, and we routinely find it hiding behind stucco when we open a wall for an addition.
- Undersized or rotting beams on hillside post-and-pier foundations. Many 1960s and 70s Tiburon homes were built on post-and-pier systems that were never intended to carry a second story. When an addition triggers an inspection, the Town requires an engineered caisson or grade-beam retrofit before vertical work resumes, and that cost belongs in the contract, not in a surprise invoice.
- View-protection design review stalls. A second-story addition that passes height limits on paper can still be denied at Planning Commission if an adjacent owner documents view impairment. This doesn’t happen in Corte Madera or Mill Valley. It happens here, and it’s why we install story poles and knock on doors before plans are final.
- Failed waterproofing behind stucco on bay-facing walls. The same salt air that corrodes fasteners also works its way behind improperly flashed stucco. By the time an addition opens up an exterior wall, we often find sheathing that needs full replacement, not patching.
Pricing for Home Additions & ADU in Tiburon, CA
Here are the ranges we quote most often for Home Additions & ADU in Tiburon. These are real numbers from real jobs on these hills, not national averages pulled from a database.
| Scope | Tiburon Price Range |
|---|---|
| Home Addition | $45,000-$130,000 |
| ADU Construction | $90,000-$220,000 |
| Garage Conversion ADU | $30,000-$80,000 |
What moves a Tiburon quote toward the top of that range is usually what’s inside the walls, not what’s on the plans. Foundation retrofits, re-sheathing, and the design review timeline all cost real money, and we’d rather tell you that before we start than hand you a change order after demolition. Every allowance is written into the contract. Every price change comes as a written change order before work touches the job. Call (877) 610-1318 for a free estimate with those numbers spelled out.
We Also Serve Cities Near Tiburon
In addition to Tiburon, our crews work regularly in Sausalito, Tamalpais Valley, Tamalpais-Homestead Valley, and Corte Madera. The permitting and foundation rules shift a little in each town, but the way we work doesn’t: permits pulled, prices in writing, and Tom’s name on the truck.
Serving Tiburon, CA - Our Local Coverage Area
We’re based in the Tiburon 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 - Home Additions & ADU in Tiburon
Because Tiburon’s view-protection ordinance is enforced neighbor-by-neighbor, not just by zoning code. A second-story addition that passes height limits on paper can still be denied at Planning Commission if an adjacent owner demonstrates view impairment. Story poles give neighbors a visible, honest preview of what’s coming, and early outreach often resolves concerns before they become a formal appeal. Call (877) 610-1318 and we’ll explain exactly what your specific lot will require.
Most 1960s and 70s Tiburon hillside homes sit on post-and-pier foundations that were never engineered for a second story. When the addition triggers a structural inspection, the Town requires an engineered caisson or grade-beam retrofit before vertical work continues. That typically adds $15,000-$40,000 depending on slope and access, and we put that line in the contract before we start, not after the wall is open.
Tiburon is a peninsula projecting into San Francisco Bay, so marine air arrives from three sides at once. Hardware, flashing, and even exterior sheathing corrode and fail significantly faster here than in Mill Valley or Corte Madera. That means an ADU addition in Tiburon needs marine-grade fasteners, upgraded flashing details, and often full exterior re-sheathing when we open a bay-facing wall. It’s not an upsell. It’s what the site requires, and we document it in writing before we close the walls.
In most cases, yes. A garage conversion works within an existing footprint, so it typically doesn’t trigger Tiburon’s discretionary design review the way a new second-story addition or detached ADU does. That’s a big part of why garage conversion ADUs in Tiburon run $30,000-$80,000 and move faster than new builds. The path still requires permits and inspections, but the view-protection hurdles are usually not in play. Call (877) 610-1318 and we’ll confirm what applies to your specific property.
We stop work, document what we found with photos and measurements, and hand you a written change order before we touch another inch. That’s the rule on every Barrett & Sons job, and it’s the rule that matters most on Tiburon’s salt-exposed walls, where rot behind stucco is common and the fix is often full re-sheathing rather than a patch. You approve the price in writing, and only then do we proceed. No surprise invoices at the end.
Call Barrett & Sons Construction for Your Tiburon Home Addition or ADU
If you’re planning a home addition or ADU in Tiburon, the sooner we walk the site, the sooner you’ll know what the Town will require and what the job will actually cost. Call (877) 610-1318 for a free estimate. Tom Barrett will answer, and he’ll tell you straight what’s ahead. No script, no call center, no surprises that weren’t on paper first.
Written by Tom Barrett, Owner at Barrett & Sons Construction, serving Tiburon since 1998.