Engineered wood flooring - These floors are constructed from several wood plies that are glued together. The centre core is generally a softer wood material and is used to make the tongue and groove. A hardwood finish layer is glued on top of the centre core and another softer wood ply is attached underneath the core. This top ply is also called the finish layer and can be constructed of almost any wood specie.
Wood always wants to expand in a certain direction. In the presence of moisture solid wood planks will always expand across the width of the planks, rather than down the length of the boards. To avoid this problem, manufacturers of engineered planks place each ply in the opposite direction of each other. This is called cross-ply construction. Once the wood layers are glued together the plies will counteract each other which will stop the plank from growing or shrinking with changes in the humidity. Engineered wood floors are designed for the floating installation and can be glued together or some now come with a click system.