Tiburon T1-11 Siding

T1-11 is the grooved plywood or OSB panel siding with the vertical channels. Mid-century builders, garage and addition framers, and backyard-studio crews all used it because it was quick to hang and inexpensive. On the Tiburon peninsula it usually shows up on older homes, converted garages, and outbuildings. After decades of wind-driven bay moisture, those panels are often the first part of the exterior to fail. Bay Area Siding Company is a Larkspur-based siding contractor, and we handle T1-11 in whichever direction your home needs:

• Replace it with a more durable panel or lap system.
• Rebuild the wall behind it where needed.
• Reinstall it where a rustic panel look is what you want and the parcel allows it.

Seeing soft corners or peeling panel edges? Request a bid or call (415) 619-5167. We'll look at the panels and tell you honestly whether they need paint, repair, or replacement.

Why T1-11 wears out the way it does

T1-11 is a wood-based sheet product, and its weak points are predictable. The face of the panel can hold paint reasonably well. The trouble starts at the places water can get into the layers:

• the bottom edges
• the horizontal seams between stacked panels
• the grooves
• any spot where the finish has worn through

Once moisture gets into the plies or strands, the panel swells, the veneer lifts, and the material can start to rot from the inside.

On a peninsula that sees marine air and weather from several directions, keeping every edge and groove sealed is ongoing work. When it slips, you'll typically see some of these signs:

• Bottom edges that are flared, crumbling, or soft when pressed, especially where panels sit close to grade, decking, or a planter.
• Veneer layers separating, with the face ply bubbling or peeling away from the core.
• Horizontal seams that have opened or sprouted Z-flashing that's rusted through.
• Paint that fails fast in the grooves even after a fresh coat, because the channels hold moisture and are hard to coat evenly.
• Staining or musty smells inside on walls that back up to the panel siding.

A single delaminated panel on a garage wall is a repair. Swelling and softness spread across several elevations usually means the panels have reached the end of their service life.

The detail that changes the scope: is your T1-11 also your sheathing?

This matters more with T1-11 than with almost any other siding, so it's worth understanding before you get bids.

On many homes, siding is a separate layer. It's nailed over structural sheathing with a water-resistive barrier (WRB) between them. Tearing that siding off exposes the sheathing and WRB so the flashing and drainage can be rebuilt.

T1-11 was often installed differently. On some older houses, additions, and outbuildings, the panels were nailed directly to the framing and act as both the siding and the structural sheathing. In that case the panels may also provide the wall's bracing.

When that's how your wall was built, removing the T1-11 opens the wall to the framing. The new scope then has to include new structural sheathing, a proper WRB, and flashing before any cladding goes back on. It's a bigger job than a typical re-side, and the bracing function has to be maintained.

When T1-11 was installed over separate sheathing, the job looks like an ordinary tear-off. The panels come off, we inspect the sheathing and WRB, and we rebuild the drainage plane.

We determine which situation you have during the walkthrough, and we confirm it when the first panels come off. You'll know before we commit to a scope.

Your options on a Tiburon home

Upgrade to fiber cement. Fiber cement vertical panels, often paired with battens, can keep the vertical character of T1-11 in a material that won't swell or rot. Lap siding is also an option if you want to change the look.

Fiber cement is noncombustible, which matters on hillside parcels (more on that below). See our fiber cement overview or the Tiburon James Hardie page for the brand-specific detail.

Move to engineered wood. LP offers SmartSide panel products that give a warm wood texture. They're lighter and easier to work than fiber cement, and their treated strands resist moisture far better than old-school T1-11. You still need to keep up with paint. Compare on our LP SmartSide page.

Go back to natural wood. Board-and-batten or other wood siding suits some Tiburon cottages and older homes. It's the highest-maintenance route, and its combustibility needs a hard look on fire-zone parcels.

Reinstall T1-11. For a studio, shed, or outbuilding where the rustic grooved look is the goal and cost is the main driver, new T1-11 can make sense. It holds up best when:

• it's installed over a proper WRB,
• every edge is sealed before hanging,
• it's kept off grade with correct flashing at horizontal joints, and
• it's repainted on schedule.

Whether it's appropriate on your specific parcel depends on the fire-zone questions below.

For the bigger-picture decision across all materials, start with our siding replacement hub or the Tiburon siding replacement page.

Tiburon rules that bear on T1-11

Permit and Design Review. The Town of Tiburon requires a building permit for siding. The Town also notes that separate Design Review approval is required for many exterior items. Swapping T1-11 for fiber cement lap siding, or changing your exterior color, is the kind of visible change that commonly falls under that review.

Tiburon takes exterior appearance seriously because hillside homes read against each other across the slope. We build the review path into the schedule. The exact submittal requirements for your parcel should be confirmed with the Town's Community Development Department.

Fire-hazard zones. Parts of Tiburon are mapped in Fire Hazard Severity Zones, up through Very High in places. The Town also has Wildland-Urban Interface areas along vegetated slopes and open space. In areas where California Building Code Chapter 7A applies, exterior wall coverings generally need to be noncombustible or ignition-resistant, or part of an assembly that meets the code's performance requirements.

Standard T1-11 is a combustible wood product. On a mapped hillside parcel, putting new T1-11 back up may not be the straightforward choice it would be elsewhere. That's often part of why homeowners there choose fiber cement.

How Chapter 7A applies depends on your parcel's designation, the product, and the scope of work. We confirm it with the Town and the Tiburon Fire Protection District rather than assume. If your property backs onto open space, mention it at the first visit.

Salt air. Many Tiburon homes take steady marine exposure. For any replacement, we choose fasteners, flashing, and trim details suited to a coastal setting, so the new wall isn't undone by corroded metal a few years in.

How the job goes

We start with a walkthrough. We look at panel condition, how the T1-11 was attached, and where water has been getting in. You then get a written scope with the material, profile, color, and any sheathing work spelled out, and we handle the permit and any Design Review submittal.

On install days, the old panels come off one section at a time. We repair or replace sheathing where it's needed, then install a new WRB and flashing. The new cladding goes on to the manufacturer's spec. We finish with trim, caulking, and paint where specified, plus cleanup and a final walkthrough with you. You can browse finished work on our projects page.

What drives the cost

We don't quote prices without seeing the house, but these are the main factors:

• Sheathing. Whether your T1-11 is doing double duty as sheathing is often the biggest swing factor.
• Hidden damage. How much rot turns up at sills, rim areas, and the bottoms of walls.
• Replacement material. New T1-11, engineered wood, fiber cement, or wood.
• Size and access. Wall area, height, and access on steep hillside lots.
• Details. Trim, window and door flashing, and paint.
• Paperwork. The permit and Design Review steps.

FAQ

Can I just repaint my T1-11 instead of replacing it? If the panels are still solid, with no swelling, soft edges, or delamination, a careful prep and repaint with the edges and grooves sealed can extend their life. Paint won't fix panels that have already absorbed water and started coming apart. At that point, replacement is the realistic option.

Do I need Town approval to replace T1-11 with fiber cement in Tiburon? Plan on it. Tiburon requires a building permit for siding, and changing the cladding material or color is the type of exterior change that often triggers Design Review. We confirm the exact path for your parcel with the Community Development Department and plan the schedule around it.

Can I reinstall T1-11 on a hillside home in a fire zone? It depends on your parcel's mapped designation and on whether Chapter 7A applies to your scope. T1-11 is combustible, so on mapped hillside parcels a noncombustible or ignition-resistant option is often the better fit. We verify the requirements with the Town and the Tiburon Fire Protection District before recommending a material.

Will removing T1-11 expose my framing? Only if the panels were installed directly on the studs as combined siding and sheathing. That's common with T1-11, but not universal. If yours was installed over separate sheathing, removal exposes the sheathing and WRB instead. We identify which you have before finalizing the scope.

Ready to deal with that T1-11?

Whether it's a delaminating garage wall or a whole house clad in tired panels, we'll give you a clear picture of what's behind them and your options. Call (415) 619-5167 or request a bid.

Replacing windows at the same time? See window replacement in Tiburon. You can also explore more of our work across Marin County.