Silver Firs, Everett T1-11 Re-Side: James Hardie Cedarmill Lap, Shingle Gables and a Bellyband

This rambler in the Silver Firs neighborhood of Everett was still wearing its original T1-11 — the grooved plywood panel siding that went onto a large share of the houses built in south Snohomish County between the 1970s and the 1990s. The panels were faded and chalking and the paint was done, but when we went over the walls they were not rotten. That one finding changed the shape of the whole job.

Instead of tearing the T1-11 off — which on a house like this means paying to re-sheathe every wall before a single board of siding goes up — we left the sound panels in place as the substrate, wrapped the house in HydroGap drainable housewrap, and installed 6-inch James Hardie Cedarmill lap siding, HardieShingle in the gables as an accent, HardieTrim casings and corners with a bellyband, a new three-lite picture window, new awning windows and a new exterior door, then painted the whole envelope in two coats of Sherwin-Williams Duration. The homeowners got a full fiber cement house, and the sheathing line item never appeared on the estimate.

Can you install new siding over T1-11?

On this house, yes — and the reason is worth understanding before you get quotes, because it is usually the single biggest number in a T1-11 re-side.

On most houses of this era, T1-11 is not just the siding. It is also the sheathing: one 5/8-inch or 3/8-inch sheet of grooved plywood nailed straight to the studs, doing the structural job and the weather job at the same time. Pull it off and you are looking at bare studs and insulation. Every wall then has to be re-sheathed in plywood or OSB before any new siding can be hung — new material on every elevation, the labor to hang it, the dumpsters to take the old panels away, and several days where the house is open to the weather.

Fiber cement does not actually care whether the flat, solid, nailable surface behind it is new plywood or old plywood. What it needs is a substrate that is dry, securely fastened and reasonably flat, with a water-resistive barrier between that substrate and the cladding. Sound T1-11, wrapped, is all of those things. So we checked, panel by panel, whether this wall qualified.

What we checked before we agreed to side over it

We walk every elevation and push on the panels where water actually lands — low on the wall, under the windows, beside the doors, and at the bottom edge where the ply likes to wick. What disqualifies a wall is soft spots, plies separating at the panel edges, swollen fuzzy edges, panels that have worked loose from the studs, or walls that are visibly out of plane. What does not disqualify it is exactly what this house had: chalky paint, faded color, open grain and tired-looking grooves.

Had we found rot, the honest answer would have been a tear-off and dry rot repair first — that is what happened on our Stanwood LP siding replacement, where the failing panels came off and the sheathing underneath needed work before anything new went up. Part of a siding inspection is being willing to tell you the expensive answer when it is the right one. Here it was not: the panels were fine, and saying so saved the customer real money.

HydroGap drainable housewrap over the old panels

Leaving the T1-11 on the wall makes the water-resistive barrier more important, not less. There is now a sheet of plywood permanently sandwiched between the new fiber cement and the framing, and that plywood needs to stay dry and be able to dry if it ever does get wet. A plain flat housewrap pressed tight between two solid layers gives incidental water nowhere to go.

So the whole house got HydroGap, a drainable housewrap with 1mm spacers molded into its face. Those spacers hold a small, continuous drainage gap between the wrap and the back of the siding, so water that gets past the cladding — at a butt joint, around a fastener, behind a trim board — runs down and out at the bottom instead of sitting against the panel. It is not a full furring-strip rainscreen, and we do not call it one: it is the drainage step that fits a re-side where the wall thickness has to stay reasonable. On jobs where we do build the full gap, like this Green Lake re-side, the furring strips go on over the wrap.

6-inch James Hardie Cedarmill lap siding

The walls are James Hardie Cedarmill lap in a 6-inch board. Cedarmill is the woodgrain-textured face, and the 6-inch width lands a narrower, more traditional reveal than the 8-inch boards that go on most new construction — a better fit for a single-storey rambler, where wide boards make a low house look lower. As a James Hardie contractor we hang it to the manufacturer’s fastening and clearance spacing, with the gaps at trim and the ground clearance the instructions call for, because that is what keeps the 30-year product warranty intact.

Fiber cement is also simply the right material for this climate. It does not feed rot, it does not interest woodpeckers, and it holds paint far longer than the T1-11 it replaced — which is the whole argument in our best siding for Washington State guide and the material comparison.

HardieShingle gables and the bellyband that ties them in

Every gable on the house and garage got HardieShingle instead of lap. It is a small change that does a lot of work: the shingle texture reads as a deliberate accent from the street, it gives the roofline a visual cap, and it breaks a plain rambler out of the single-texture look that T1-11 gives a house by default.

Underneath each gable runs a bellyband — a wide horizontal HardieTrim board at the transition. It is the detail people notice without knowing what they are looking at. Visually it splits a tall gable wall into two readable parts and gives the shingles a clean place to land. Practically, it is a flashed, deliberate horizontal break between two different claddings rather than a raw butt joint. On the garage wall it is what makes the whole elevation look designed instead of just covered.

New windows and a door, to get light into the house

Because the budget was not being spent on sheathing, it could go somewhere the homeowners would actually notice. The gable end facing the back garden had been a completely blank wall of T1-11 — you can see it in the before photo above. It now carries a three-lite picture window. A pair of awning windows went into other walls, and the back of the house got a new exterior door.

Cutting new openings during a re-side is the cheapest time to do it, because the wall is already open and the WRB is being installed anyway. Every new opening was framed and flashed into the HydroGap as the wrap went on — sill flashing first, jambs lapped over it, head flashing lapped under the wrap above — so each window drains onto the drainage plane rather than behind it. The existing windows that stayed were re-flashed and re-trimmed at the same time, so the entire envelope ends up on one continuous barrier instead of a patchwork of old and new details.

Two coats of Sherwin-Williams Duration

The siding went up factory-primed rather than pre-finished, and our crew painted it on site: two full coats of Sherwin-Williams Duration over the primer, with the HardieTrim in cream and the existing soffit and fascia repainted to match so the finished envelope reads as one piece.

Field painting is the reason this house is the color it is. The deep magenta the homeowners chose is not in the factory-finished ColorPlus range — pre-finished siding only comes in the colors the factory offers. Primed board plus a good field coat means any color in the fan deck is available, which matters a great deal to homeowners who know exactly what they want. The trade-off is that the finish is now on a repaint cycle rather than a factory warranty, and with a quality acrylic on properly primed fiber cement that is a long cycle.

The takeaway: a fiber cement house without the sheathing bill

The cheapest part of any siding replacement is the work you can honestly skip. On this Everett house that was the tear-off and the re-sheathe — not skipped to cut corners, but skipped because the existing T1-11 was inspected, found sound, and put to work as the substrate it already was. What the homeowners got instead was a drainable WRB, a full James Hardie envelope with a shingle-and-bellyband detail that gives a plain rambler some character, three new openings that changed how the inside of the house feels, and a paint color that is entirely theirs.

If your house still wears its original T1-11 and you are wondering whether it has to come off, that is a question worth answering before you budget for the answer. We are Everett-based, so we can usually come and push on your walls within a few days. See our siding cost guide for how the numbers break down either way.