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Window detailing for T-111 siding

Q: I’m installing T-111 plywood siding on an outbuilding with several windows and doors. How should I flash the windows and doors?

Humphrey Russel, Woodbury, CT

A: John LaTorre, a contractor in Tolumne, California, replies: T-111 is best installed over tar paper or housewrap stapled to studs. The best option for windows is the type with a vinyl flange all the way around. Weatherproof the opening using self-adhering flashing such as Grace Vycor (www.graceconstruction.com), as shown in the drawing. Install the window, and tape the flanges to the housewrap or tar paper with flashing tape such as Tyvek Contractor Tape.

Now you simply side around the window. You can add any style of trim without affecting the weather performance. If you choose a protruding exterior sill and built-up top trim, make sure the sill slopes away from the house, and if the protruding top is not well protected by the roof overhang, add a small piece of L-shaped flashing on top, which is caulked fast to the T-111. If your windows have brick mold instead of flanges (your door is most likely configured this way), weatherproof the opening the same way, but skip the Tyvek tape. Side around the brick mold. Leave 1/8 in. or so between the window or door and the T-111 for caulk.