T111 (also referred to as T1 11, T1, and T1-11) is a siding material made of laminated plywood or strand board panels. Its durability makes it a popular choice compared to other forms of wooden siding. The T stands for textured, a reference to the grooves carved into the surface.
Created in the 1960s, T111 made from plywood is a little more resistant to moisture damage than the kind made from OSB (oriented strand board, also known as waferboard), as it contains fewer natural grains. Accordingly, plywood T111 is a little pricier, but it also has a more elegant look, since it's often constructed with long strands that imitate natural wood.
Often constructed from southern pine, T111 is valued for its combination of resilience and flexibility. It's easy to cut, making it convenient for use around tricky roof edges. Despite its lamination, T111 usually needs to be treated, either with stain or paint, and requires flashing to reliably protect the walls it covers.