What Is T11 Wood Siding?

T1-11 is an exterior wood siding product made from plywood, wood composite or oriented strand board, which is a layered board made of compressed wood chips. If treated with chemicals that fight decay and rot, the siding will be noted as a treated wood siding product—an important requirement for outdoor use. However, this notation does not mean the plywood siding is waterproof and thus painting is recommended for best results. Common thickness for a T1-11 panel includes 5/8 and 19/32 inches.

T1-11 siding is plywood siding with parallel grooves across the surface. Grooves are channels cut into the board to recreate the look of various wood siding styles such as shiplap, clapboard and board and batten. Grooves are created according to a specific width and noted in the product's specifications. For instance, grooves made every eight inches are referred to as eight inches on center or OC. Panels are sized at four by eight or four by nine feet and are cut on site to fit construction needs. Finish textures include scratch sanded, rough sawn and plain. Lap styled T1-11 can be ordered with beveled or square edges.

Southern pine is a popular choice for T1-11 siding. Cedar, Douglas-fir and redwood are also used to create the siding. A mix of these and other wood species may be found in T1-11 oriented strand board siding.

Proper installation of T1-11 is necessary to prevent delamination and deterioration of the wood. T1-11 must be flashed and sealed against the weather according to the manufacturer's specifications. Incorrect installation can void any warranty or guarantee provided with the product. The Engineered Wood Association recommends painting all blind and exposed siding edges and protecting all exposed surfaces while under construction by using plastic sheeting or other means to keep the T1-11 dry until installation is complete.