Tongue and groove decking refers to boards of wood or composite material that are cut or molded with a groove — a long notch in the side of the board — on one edge and a protrusion — called the tongue — on the other. The tongue is cut to fit snugly into the groove of the adjacent board, and both the tongue and the groove are cut the entire length of the decking. The purpose is to create an attractive and strong surface with the look of natural wood and superior strength similar to mortise and tenon joinery.
Tongue and groove decking is produced using a wide variety of materials. It is commonly made from such woods as southern pine, cedar, redwood, spruce, and Ipe. Costs and availability vary among these woods, with pine and spruce generally the least expensive and Ipe, a neotropical hardwood noted for insect and weather resistance, being the most expensive.
Composite tongue and groove decking might incorporate a variety of synthetic materials, often using some wood fibers to give the look and feel of natural material. Among the most common synthetics are virgin and recycled polymers, polyvinyl chloride (PVC), polyethylene, recycled plastics, and polymer resins. The cost for tongue and groove decking made with most of these materials will fall between similar decking made from soft conifer boards and Ipe.
Advantages of composite tongue and groove decking include durability and uniformity. While natural woods, especially pine, will warp and need correction during installation, composite tongue and groove decking does not absorb moisture or warp. An additional advantage in composite tongue and groove decking made of recycled plastic or recycled polymer is the “green” use of resources.
While the most common use is for tongue and groove porch decking, roofs and interior ceilings are also built using tongue and groove wood decking. For a rustic look in a home or cabin, standard width tongue and groove decking is applied to ceilings in place of gypsum wallboard or other traditional material. Application techniques of the decking are the same as for a porch or pool deck.
Tongue and groove roof decking is a more specialized material and is not commonly found in most building supply stores. Often used in all-wood structures such as timber frame or log, it is used to create an all-wood look and feel. Tongue and groove roof decking is often made of thicker-than-standard material, ranging from 2 inches (about 5 cm) to 4 inches (about 10 cm). Tongue and groove roof decking might have two sets of grooves and corresponding tongues cut into the material.