Multi-layer Engineered Wood Floors are generally 5, 7,9 or more thin sheets of wood that are laminated together to form one plank. In the construction of engineered wood floors the wood plies are stacked on top of each other but in the opposite directions. This creates a wood floor that is dimensionally stable and less affected by moisture. This means you can install these floors over concrete slabs in basements, as well as anywhere else in the home. Because engineered wood floors are made up of several layers of wood that are all glued together its possible to change the top finish layer to a totally different wood specie without driving the costs out of sight. So if you want to choose from a variety of domestic and exotic hardwoods than you should definitely look at an engineered wood floor.