T1-11 is the grooved plywood or OSB panel siding you'll find on plenty of Los Gatos properties built or updated from the 1960s through the 1980s — mid-century tract homes, hillside cabins, garages, sheds, and additions. Installed vertically, it's an inexpensive, rustic-looking way to clad a wall, and when it's kept painted and sealed it does its job. The trouble is that most of the T1-11 still on Los Gatos homes is well past the point where that upkeep was reliably happening, and by the time homeowners call us the question is usually less "should I install T1-11?" and more "what do I do about the T1-11 I've got?" We handle both conversations.

Get a straight assessment. Call (415) 619-5167 or request a bid.

The usual Los Gatos situation: failing T1-11

Because T1-11 is a wood-panel product, its weakness is water. Where paint has thinned, where the shiplap edges or bottom edges weren't kept sealed, or where flashing above the panels was marginal, moisture gets in and the panel swells, checks, and eventually delaminates — the plies literally separating. On a hillside home shaded by the tree canopy that's common on the wooded lots here, panels can stay damp longer and go faster. The telltales:

• Swollen, soft, or spongy panels, especially along the bottom edge and at butt joints.
• Face plies peeling or bubbling away from the core.
• Dark staining, mildew, or visible rot at the base of walls.
• Paint that won't hold no matter how often it's redone.

Once a panel is delaminating, patching and repainting is throwing money at a wall that's already failing. The durable fix is replacement.

What we replace it with

Most Los Gatos T1-11 replacements move to a longer-lived material, and which one depends on where the home sits:

• Fiber cement — the common upgrade, and the right one on a hillside parcel: noncombustible, rot- and pest-proof, and far more stable than plywood. Los Gatos is served by the Santa Clara County Fire Department and parts of town lie in mapped Fire Hazard Severity Zones, so on a designated parcel, moving off a wood panel to a noncombustible board is both a durability and a fire-hardening improvement. Whether Chapter 7A formally applies is a Town and County Fire confirmation tied to your parcel and scope.
• LP SmartSide — engineered wood, if you want to keep a warm wood look with better moisture and impact resistance than old T1-11 (though, being wood-based, not the pick for a fire-hazard parcel).
• New T1-11 or a panel look, where the rustic vertical-panel aesthetic is genuinely wanted — a cabin-style hillside home, an outbuilding — and the parcel doesn't call for noncombustible cladding. We'll install it correctly, with the edge sealing and flashing that make it last, and be honest that it will need a diligent repaint cycle.

What removal reveals

Pulling failed T1-11 exposes the sheathing or substrate and the water-resistive barrier (WRB) and flashing behind it — and with a panel product that's been letting water in, this is where the real story shows. Sometimes the T1-11 was doing double duty as both siding and sheathing, in which case removal exposes the framing directly and the wall needs a proper sheathing-and-WRB assembly rebuilt behind the new cladding; sometimes there's separate sheathing underneath with a degraded WRB and localized rot to correct. Either way, we assess what's actually there, repair damaged material, and establish a sound WRB and flashing sequence before new siding goes on — the step that keeps the next wall from failing the way this one did.

Permits and cost

Siding replacement in Los Gatos is permitted through the Town of Los Gatos Building Division, and on a historic property or a fire-designated parcel we confirm the applicable review or requirement first. We manage the paperwork. Cost depends on how much of the T1-11 is failing, what condition the substrate is in once panels come off (this is the big variable with water-damaged panel siding), the replacement material you choose, wall area and access, and any framing repair a doubling-as-sheathing situation turns up. We measure and assess before quoting.

FAQ

Should I repair or replace my T1-11 siding? If panels are swelling, delaminating, or rotting, replacement is the durable answer — patching a plywood panel that's absorbing water rarely holds. If the panels are sound and just need paint and sealing, maintenance may buy time. We assess the actual condition and tell you which situation you're in.

What's the best material to replace T1-11 with in Los Gatos? For most homes, fiber cement — it's noncombustible and far more stable than plywood, which matters especially on a hillside fire-hazard parcel. Engineered wood is an option where you want a wood look off a non-fire-zone parcel. We match the material to your home and location.

Can I just put new siding over the old T1-11? We don't recommend it. Covering hides water damage and can trap moisture against a substrate that's already compromised. Removing the old panels lets us inspect and repair the sheathing, WRB, and flashing — the point of doing the job right.

Is T1-11 okay on a Los Gatos hillside home? As a wood-based panel it's combustible, so on a fire-hazard-designated parcel it's not the appropriate material — noncombustible fiber cement is. We confirm the parcel's designation with the Town and County Fire before recommending anything.

Let's deal with your T1-11

Call (415) 619-5167 or request a bid. We'll assess the panels and the wall behind them and lay out repair or replacement honestly. Compare replacement materials: fiber cement, LP SmartSide, CertainTeed, and wood. We serve the South Bay, keep finished work in the project gallery, and also handle siding replacement and window replacement in Los Gatos.