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T1-11 Siding paint calculator

T1-11 is grooved plywood or OSB siding, common on garages, sheds, and budget-built homes. The rough face and porous wood pull coverage down to about 225 sq ft per gallon, and the vertical grooves swallow even more. Treat it like the exposed wood it is: prime every bare and weathered board, <strong>caulk the seams and flashing</strong>, and lay on two coats of exterior acrylic. Kept sealed, exposed T1-11 still needs a repaint every 5 to 7 years — water at the grooves and bottom edges is what ages it.

House perimeter × wall height. Subtract windows + doors.

How much paint for t1-11 siding

T1-11 Siding covers about 225 sq ft per gallon for a two-coat job. To find your siding area, multiply the house perimeter by the wall height and subtract windows and doors. For a typical 2,400 sq ft of siding, that's about 21.50 gallons of topcoat plus about 8 gallons of primer. Always round up to the nearest gallon — exterior batches are harder to color-match on a second trip.

In paint alone, that 2,400 sq ft example runs about $753–$1398 at $35–$65 a gallon for quality exterior acrylic, before primer and supplies. Enter your real siding area above and pick a brand in the result panel for an exact figure.

The Grooves Drink The Paint

T1-11's vertical grooves are deep, rough, and partly end-grain, so they grab brushes and soak up far more paint than the flat field. Roll the broad faces with a 3/4-inch nap to push paint into the texture, then go back and brush each groove by hand so the channel is fully coated. Spraying alone bridges the grooves and leaves them thin — back-brush or back-roll behind the gun every time, or those lines fail first.

Caulk Seams And Flash Before Coating

T1-11 expands and contracts hard with the seasons, and water loves its joints. Before the topcoat, run fresh paintable elastomeric caulk along vertical butt seams, around windows and doors, and anywhere trim meets the panel. Confirm horizontal joints have proper Z-flashing — caulk alone won't hold there. Leave the bottom drip edge open so the wall can drain. Skip this and water wicks behind the panel, delaminating the plywood from the inside out.

Prime Every Bare And Weathered Board

Plywood and OSB siding are thirsty and uneven; the grooves expose end-grain that drinks differently than the face. A full coat of exterior wood primer seals the surface so the topcoat lays down evenly instead of flashing dull in the porous spots. On sun-grayed or previously painted-and-peeling T1-11, sand back to a sound surface first, then prime. Bare OSB-core panels especially must be sealed on all edges, or they swell and crumble.

Seal Bottom Edges And Watch The Sun

The single biggest killer of T1-11 is water entering the unsealed bottom edge and end-grain, then swelling and rotting the plywood plies. Prime and paint the bottom cut edges, keep them an inch or two above grade and decking, and re-caulk any opening trim as it ages. Paint in mild, dry weather — 50 to 85 degrees, out of direct sun — so coats cure properly rather than skinning over on a hot, thirsty panel.

Exterior paint cost by brand

Coverage is similar across the major exterior lines, so the price tier is what moves your bill. Current per-gallon prices for the brands the calculator can price for you:

Brand & linePrice / galCoverage
Backdrop Exterior~$69/gal400 sq ft/gal
Behr Marquee~$52/gal400 sq ft/gal
Behr Ultra~$45/gal400 sq ft/gal
Behr Premium Plus~$33/gal400 sq ft/gal
Benjamin Moore Aura Exterior~$85/gal400 sq ft/gal
Benjamin Moore Regal Exterior~$70/gal400 sq ft/gal
C2 Paint Guard~$65/gal350 sq ft/gal
Diamond Vogel Artistry~$42/gal400 sq ft/gal
Diamond Vogel Palisade~$52/gal400 sq ft/gal
Dunn-Edwards Evershield~$72/gal400 sq ft/gal
Dutch Boy Maxbond Plus~$42/gal375 sq ft/gal
Glidden High Endurance Plus~$28/gal400 sq ft/gal
HGTV Home by Sherwin-Williams WeatherShield~$50/gal375 sq ft/gal
Kompozit ONE~$40/gal388 sq ft/gal
Kompozit PRO~$52/gal388 sq ft/gal
Magnolia Home Exterior~$50/gal400 sq ft/gal
PPG Manor Hall~$55/gal400 sq ft/gal
PPG UltraLast~$48/gal400 sq ft/gal
Rodda Horizon Exterior~$56/gal375 sq ft/gal
Sherwin-Williams Emerald Exterior~$86/gal400 sq ft/gal
Sherwin-Williams Duration~$80/gal400 sq ft/gal
Sherwin-Williams SuperPaint~$60/gal400 sq ft/gal
Sherwin-Williams A-100~$49/gal400 sq ft/gal
Sherwin-Williams Resilience~$73/gal400 sq ft/gal
Valspar Duramax~$50/gal350 sq ft/gal

Frequently asked questions

Do I need to prime T1-11 before painting?+
Yes, on any bare, repaired, or sun-faded T1-11. The plywood face is porous and the grooves expose end-grain, so an exterior wood primer seals everything and keeps the topcoat from soaking in unevenly and flashing dull. Over old sound paint you can often skip full priming, but always spot-prime bare wood, repairs, and any area you sanded back to raw fiber.
How often does T1-11 need repainting?+
Plan on repainting exposed T1-11 every 5 to 7 years, with south- and west-facing walls weathering fastest. The finish's lifespan rides almost entirely on water control — keeping the grooves coated, the seams caulked, and the bottom edges sealed. A wall that stays sealed easily reaches the seven-year mark; one with open seams can need attention in three.
Should I paint or stain T1-11 siding?+
Either works, but they age differently. Paint gives a durable, fully opaque finish and seals the porous plywood best against moisture, which is usually the priority on T1-11. Solid stain is easier to recoat down the road since it fades instead of peeling, but it offers less of a moisture barrier. For exposed walls prone to water at the grooves, a primed paint system is the safer bet.
How do I fix swollen or delaminating T1-11?+
Swelling and delamination mean water got into the plywood plies, usually through an unsealed edge or open seam, and that wood won't recover — cut out and replace any spongy or peeling sections. Then prime all edges of the new panel, caulk the seams, flash the horizontals, and seal the bottom drip edge. Painting over swollen panels only hides the rot while it spreads.
What sheen is best for T1-11 siding?+
A satin or low-luster exterior acrylic is the sweet spot. Flat hides the rough texture and surface flaws but holds dirt and is harder to wash; high gloss highlights every groove imperfection and looks unnatural on rustic plywood. Satin sheds water and dirt well, cleans up easily, and reads as a soft, even finish across both the flat field and the grooves.
Can I spray-paint T1-11 instead of rolling?+
You can spray for speed, but you cannot spray alone. The gun lays paint on the flat faces fine yet bridges over the deep grooves, leaving them thin where the siding fails first. Spray a section, then immediately back-brush or back-roll to drive paint into every groove and into the rough texture. Spray plus back-brushing gets you fast coverage without sacrificing the grooves.
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