T1-11 is an engineered plywood product. It provides an easy and efficient method for siding rustic structures like barns and sheds, and is commonly used on houses as well. It comes untreated, so you have to paint or stain it after installation if you want it to last and provide maximum weather resistance. The sheets are grooved, so that the edges will seal when you nail them together, but you need to install flashing, caulking and trim along the top and bottom edges and around windows and doors to keep water out.
Cover the house framing with tar paper or house wrap before hanging T1-11 siding. Staple the paper horizontally to the studs, starting at the bottom of the wall and working up. Overlap each successive layer two or three inches over the top of the layer under it.
Install the sheets of T1-11 vertically, starting at the top left-hand corner of the wall, nailing them to the studs with two-inch galvanized nails. Be sure there is a stud under the right edge of each sheet, and nail the edge to the stud. When you install the next sheet, be sure to nail the left-hand edge to the same stud. Nailing the edges in this way will produce a watertight seal.
Install Z-flashing on the top of each sheet so that one branch of the Z hangs over the top. Nail the other branch to the wood behind the T1-11. If the wall requires more than one sheet to cover its vertical span, install the flashing on the top of the lower sheet with one branch of the Z inserted behind the upper sheet.
Trim the siding with one-by-four-inch wooden trim, covering the gaps around windows and doors, under the soffit and on the corners of the house. Nail the trim with two-inch galvanized nails, then caulk around it with acrylic latex caulk.
Cover the siding and the trim with high quality wood primer if you plan to paint, rather than stain, it. The primer will seal the grain better than paint and provide a substrate that will give the paint better adhesion. While you can brush or roll the primer, it will penetrate the rough-sawn grain better and provide a better seal if you spray it with an airless sprayer. Cover the primer with one or two coats of acrylic latex house paint.
Stain the T1-11 with a pigmented stain if prefer to let some of the grain show through. The more pigment in the stain, the better it will protect the siding from the deteriorating effects of the sun's UV rays. The stain will soak quickly into the siding, so use an airless sprayer to avoid leaving patches that you will have to re-coat.