Novato T1-11 Siding

If your Novato home has T1-11, you already know it by the look: tall grooved plywood or OSB panels, run vertically, with that rustic board-and-batten-ish rhythm. It went on a lot of mid-century houses, sheds, and older tracts because it was fast and cheap, and when it's kept sealed and painted it can last a long time. The trouble is that most of Novato's T1-11 is now decades old, and once water gets past the finish it fails in a predictable way — swelling at the bottom edge, delaminating plies, soft spots, crumbling around fasteners. Bay Area Siding Company works with T1-11 across northern Marin, whether that means keeping a rustic look going or, more often, replacing failed panels with something that lasts longer.

Not sure which way to go? Call (415) 619-5167 or request a bid.

Why T1-11 fails, and why Novato is hard on it

T1-11 is a wood-based panel, and wood-based panels live or die by the finish protecting them. Inland Novato runs a punishing cycle for that: dry, UV-intense summers from about June through September, then most of the year's rain concentrated December through February. That bake-then-soak swing is exactly what breaks down old paint and caulk, and once the film cracks, moisture wicks into the plywood at the grooves and the bottom edge. From there it swells, the plies separate, and the panel starts to rot. On the ranch homes and older tracts around San Marin, Pleasant Valley, and downtown Novato, that's the story we see repeatedly — panels that were fine for thirty years and then went quickly once the finish gave out.

Repair, replace in kind, or upgrade

There are three honest paths, and the right one depends on how far gone the panels are and what you want the house to look like:

• Spot repair and reseal. If only a few panels are damaged and the rest are sound and well-sealed, replacing the bad panels and getting the whole wall properly caulked and painted can buy real time. This is the least expensive route and it makes sense when the failure is localized.
• Replace T1-11 with new T1-11. Where you specifically want to keep the rustic, vertical-groove look — common on cabins, ADUs, and homes where the style is the point — we can re-side in kind. It's still a wood panel that needs diligent sealing, but the look is preserved.
• Upgrade to a longer-lived material. The most common decision in Novato is to stop fighting the panels and switch to something that doesn't rot on this cycle — LP SmartSide if you want to keep a real wood-grain look with far less upkeep, or fiber cement / James Hardie if you want noncombustible and essentially maintenance-free apart from repainting.

The fire-zone angle changes the math on the edges

If your home sits on one of Novato's wooded or open-space edges — around Indian Valley, Black Point and Green Point, or Bahia — the T1-11 question isn't only about durability. Parcels in those higher-hazard Wildland-Urban Interface areas can fall under California Building Code Chapter 7A, which generally steers exterior walls toward noncombustible or ignition-resistant assemblies. T1-11 is combustible plywood, so on a 7A parcel, re-siding in kind may not be the appropriate route, and fiber cement becomes the sensible target. Whether 7A applies depends on your parcel's fire-hazard designation and the scope of the work, so if you back up to wildland fuels, we confirm the classification with the Novato Fire Protection District and the City before recommending a path. On the flatland core, this doesn't come into play, and all three options above are open.

What tear-off tells us

Whichever direction you choose, if panels are being removed we take the chance to look behind them. Pulling failed T1-11 exposes the sheathing and the water-resistive barrier, and on homes this age we frequently find the reason the panels failed in the first place — missing or degraded flashing at windows, a WRB that predates modern standards, or dry rot in the sheathing itself. We correct what the tear-off reveals and re-establish flashing and the drainage plane before new siding goes up, so the new wall doesn't inherit the old wall's problem. In Novato, a like-for-like siding replacement can run through the City's Residential Express Permit; changing to a different material or altering the wall can move it into standard review, and we confirm the current submittal path with the Building Division.

Cost drivers

No honest number posts online. What drives a T1-11 job: whether you're spot-repairing, replacing in kind, or upgrading to a new material; how many panels are involved and how much substrate repair the tear-off uncovers; the home's size and stories; and access. A spot repair is modest; a full upgrade to fiber cement is a larger investment that buys a far longer-lived wall. We price after we see the panels.

FAQ

Can you just replace the few bad T1-11 panels on my Novato house? Often, yes, if the rest of the wall is sound and well-sealed. We'll replace the failed panels and get the whole wall properly caulked and painted so the repair actually holds. If the failure is widespread, we'll be honest that a re-side is the better spend.

Should I re-side in T1-11 again or switch materials? If you love the rustic look and you're not on a fire-zone parcel, re-siding in kind is legitimate. But most Novato owners switch to LP SmartSide or fiber cement to stop the rot-and-repaint cycle. We'll lay out both.

My home borders open space — can I keep T1-11? Maybe not, if the parcel is in the Wildland-Urban Interface or a higher fire-hazard zone, where Chapter 7A points toward noncombustible walls. We confirm your parcel's designation with the Fire District and City before speccing so you're not guessing.

Why does my T1-11 keep failing at the bottom? That's the classic pattern: water wicks into the plywood at the base and the grooves once the finish cracks, and the panel swells and delaminates from the bottom up. It's a sign the panels — and the finish protecting them — have reached the end of their service life.

Get started

Let's figure out the right move for your Novato T1-11 — repair, replace, or upgrade. Request a bid or call Bay Area Siding Company at (415) 619-5167. See finished work in our project gallery or the wider Marin service area.