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
Adding onto a Tiburon home almost always costs more than the first number a contractor writes down. That’s not because contractors are dishonest. It’s because opening up a 1960s hillside addition reveals salt-corroded framing, undersized joists, and waterproofing that gave up years ago. A typical home addition in Tiburon runs $45,000-$130,000, and a detached ADU runs $90,000-$220,000. Those ranges reflect the reality of building on steep lots near the Bay with a discretionary design review process unlike any other in Marin. Home Additions & ADU work here demands a crew that knows the Town’s view-protection ordinance, its foundation requirements, and its inspection quirks before the first story pole goes up. Call (877) 610-1318 and we’ll walk the property with you before you spend a dollar on plans.
Why Barrett & Sons Construction Is Tiburon’s Preferred Home Additions & ADU Company
Tom Barrett and his sons run our crews. They’re on-site most days, not someone in a call center reading off a script. We’ve spent 29 years earning the trust of homeowners around Tiburon, and the reason is simple: every change order is written before any work changes, every permit is pulled, and every job carries our 90-Day Done Right Promise. If it’s not done right, one call brings Tom back.
The Town of Tiburon’s design review process trips up contractors who don’t work here regularly. They show up, start framing a second story, and then learn the hard way that a neighbor’s view claim can stop the project mid-permit. We install story poles and meet with adjacent property owners before we ever submit for a building permit. That’s not extra work to us. It’s how additions actually get approved in this town.
We answer the phone live, 24 hours a day, 7 days a week. You won’t get a voicemail box or an out-of-state dispatcher. You’ll get one of us. And our location in the San Francisco Bay Area means our crews serve Tiburon directly, with no trip charge inside the county. Look up Tom Barrett’s name, address, and license number before you sign anything. We publish it all.
Our Home Additions & ADU Services in Tiburon
We handle the full range of Home Additions & ADU in Tiburon work, from simple room additions to fully engineered second-story builds and detached ADUs. Four services make up most of what we do here:
ADU Design & Permitting
In Tiburon, a detached ADU is never just a small house in the backyard. It’s a project that has to survive salt-laden marine air, steep slope setbacks, and a Town Planning Commission that reviews view impacts neighbor-by-neighbor. We handle the design, the story poles, the neighbor outreach, and the full permit package. You get a written scope before the first dime is spent.
Garage Conversion ADU
Converting a garage on a 1960s-70s Tiburon hillside home usually means dealing with foundation issues first. Most of these garages were built on slabs that were never designed for living space, and decades of Bay air have attacked the rebar. We inspect the slab, test for vapor intrusion, and write the foundation upgrades into the allowance before permit submittal. That keeps your budget honest.
New Detached ADU
New detached ADUs in Tiburon run $90,000-$220,000 depending on slope, access, and foundation type. Most hillside lots here require engineered caisson or grade-beam foundations, which normal flat-lot builders don’t quote. We do. Our quotes include the geotech work, the caissons, and the drainage upgrades, all in writing.
Junior ADU & Interior Conversion
Attached JADUs and interior conversions are the fastest path to rental income in Tiburon, but they still trigger code upgrades once walls are open. Older homes here frequently need electrical panel upgrades, shear wall retrofits, and new egress windows to pass inspection. We scope those into the contract so you’re not surprised by a red tag at final inspection.
What happens when you call
- 1
A real person answersNo phone trees - you reach a local pro.
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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 don’t install mystery materials off a van. Our crews work with brands you can look up, including GAF for roofing and waterproofing details and Schluter for shower and wet-area systems inside ADU bathrooms. For windows on a new second-story addition, we rely on Andersen for structural integrity and marine-grade hardware that lasts in Tiburon’s salt air. We keep local stock and have the supply chain relationships to get materials up the hill without delays.
Common Home Additions & ADU Problems We See in Tiburon Homes
- Salt-corroded framing and hardware. Tiburon is nearly surrounded by San Francisco Bay, and the marine air hits structural connectors from three directions. Simpson ties, joist hangers, and deck fasteners rust at double the rate we see in Corte Madera or Tamalpais Valley. Any addition that opens an existing wall or floor reveals this, and the fix gets written into a change order before we proceed.
- Post-and-pier foundations on steep slopes. Most 1960s-70s hillside homes here sit on post-and-pier foundations that were fine for their original footprint but fail modern lateral load requirements once you add square footage. The Town requires engineered caissons or grade beams on nearly every hillside addition. If your first quote doesn’t include geotech, it’s not a real quote.
- View-protection denials after story poles go up. The Town of Tiburon enforces its view ordinance neighbor-by-neighbor. A second-story addition can pass the height limit on paper and still get denied at Planning Commission if an adjacent property owner demonstrates view loss. We install story poles and talk to neighbors before you spend money on framing plans.
- Undersized joists under cantilevered decks. We regularly open up older hillside additions and find 2×6 joists that have deflected under cantilevered decks, with failed waterproofing above them. Code-triggered upgrades to 2×10 or engineered lumber are common, and they’re not optional. They come with the building permit.
Pricing for Home Additions & ADU in Tiburon, CA
Here’s what you’ll actually pay in Tiburon, based on the work we do here every year:
| Project Type | Typical Range in Tiburon, CA |
|---|---|
| Home Addition | $45,000-$130,000 |
| ADU Construction | $90,000-$220,000 |
| Second Story Additions | $45,000-$130,000 |
What moves the number? Slope, foundation type, and view-review complications. A flat-lot room addition in the flatlands near the ferry terminal starts lower than a hillside second story above Paradise Drive. Caissons, grade beams, retaining walls, and story-pole delays all push toward the top of the range. We give you a written line-item quote with every allowance spelled out, and no line item changes without a written change order. Call (877) 610-1318 to schedule a free estimate in Tiburon.
We Also Serve Cities Near Tiburon
Our crews work throughout southern Marin, including Sausalito, Tamalpais Valley, Tamalpais-Homestead Valley, and Corte Madera. If you live just over the hill in any of those communities and are planning a home addition or ADU, we’re nearby and we answer the phone. No trip charge inside the county.
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
The Town of Tiburon requires story poles because its view-protection ordinance is enforced neighbor-by-neighbor through discretionary design review, not only by zoning code. A second-story addition that meets the height limit on paper can still be denied or redesigned at Planning Commission if an adjacent property owner demonstrates view impairment. We install story poles and meet with the affected neighbors before we submit the building permit package. That front-end work prevents the costly redesigns that happen when homeowners skip this step. Call (877) 610-1318 to talk through the story-pole process for your specific lot.
Most 1960s hillside homes in Tiburon were built on post-and-pier foundations that don’t meet current lateral load requirements once you add square footage. The Town typically requires engineered caisson or grade-beam foundations, shear wall retrofits, and sometimes a full foundation replacement under the new addition. We saw this on a hillside home above Paradise Drive, where salt-corroded Simpson ties and undersized 2×6 joists had deflected under the cantilevered deck. We re-engineered the load path with a new grade-beam at the deck line, filed a revised scope with the Town, and passed inspection before closing the subfloor. Get the geotech in the original quote. If it’s not there, it’s coming anyway.
Salt air from San Francisco Bay attacks metal connectors, rebar, and flashing at roughly double the rate you’d see just a few miles inland in Tamalpais Valley. In a garage conversion, the original slab was never designed for living space, and the rebar inside it has likely been oxidizing for decades. We test for vapor intrusion, specify marine-grade hardware and flashing, and write any slab remediation into the allowance before the permit goes in. Skip the testing and you’ll be chasing corrosion under the floor for years.
You’re not legally required to notify neighbors before applying for a detached ADU permit in Tiburon, but the Town’s discretionary design review gives adjacent property owners a formal way to raise view-impact objections. A project that ignores this reality can stall for months. We treat pre-application neighbor outreach as standard practice on every ADU here. It clears the path and keeps the permit moving. Call (877) 610-1318 to discuss how view-protection review applies to your specific lot.
Look for corroded framing connectors, undersized joists, and failed waterproofing. In a 1960s-70s Tiburon hillside addition, decades of salt-laden marine air typically leave Simpson ties rusted, joist hangers compromised, and cantilevered decks deflected. Undersized 2×6 joists are common, and code upgrades to 2×10 or engineered lumber get triggered once the floor is open. This is exactly what we found above Paradise Drive on a recent project, and it’s why we inspect first, write every revision into a change order, and never surprise you with an invoice at the end. A free estimate with us includes a straight answer about what your addition is going to need. Call (877) 610-1318.
Written by Tom Barrett, Owner at Barrett & Sons Construction, serving Tiburon and surrounding Marin communities since 1998.