Tongue-and-groove flooring is made up of individual boards with special interlocking edges that are hidden once the boards are installed in the finished surface. Each piece has a tongue (a continuous ridge or tab) along one side and one end of the board and a groove (a channel) along the other side edge and end. The grooves of each piece fit over the tongues of the neighboring pieces, locking the pieces together so the boards stay flat and resist movement. The quintessential tongue-and-groove flooring material is solid hardwood planks, but there are several other types of wood flooring (and even vinyl) that fall into this category.
Solid-Wood Tongue-and-Groove Flooring
Solid-wood tongue-and-groove flooring is the wood flooring found in many old homes and is the most common type of wood flooring used for basketball courts and bowling alleys. Each piece is a strip of solid wood that is typically 5/8 or 3/4 inch thick.
Solid-wood flooring is sold in unfinished and prefinished forms. Unfinished flooring is first installed, then it is sanded flat and finished by the installer. Prefinished flooring has a durable finish applied at the factory and does not need to be finished after the installation. Flooring finish typically includes the application of a wood stain for consistent coloring, then several layers of a protective topcoat, such as clear polyurethane.
Engineered Tongue-and-Groove Flooring
Engineered tongue-and-groove flooring is similar to solid-wood flooring but has a plywood-like construction consisting of thin layers of wood glued together to form a plank. The top layer is usually hardwood and is typically prefinished. Engineered flooring offers more installation options and applications than solid-wood tongue-and-groove flooring.
Laminate Tongue-and-Groove Flooring
Laminate flooring is made of fine particles of wood glued and pressed into a solid plank to serve as the base. Each plank is then topped with a thin photographic film (and a clear protective layer) to mimic the look of real-wood flooring. The planks are relatively thin—about 8 to 12 millimeters—and have special tongue-and-groove edges that lock together (not just slide into one another, like traditional tongue-and-groove joints), allowing them to be installed without nails or glue. Many engineered tongue-and-groove flooring types also have these special locking, or "click-together," edges.