The best engineered wood floors are built having 3-12 multiple ply layers (see picture below) that are cross layered, glued and pressed together. The inner core layers are are generally built up with either a hardwood and/or soft plywood type of material, which incorporates the tongue and groove fastening system along the edges of the boards. The top thicker hardwood veneer wear layer is then glued and pressed on the top surface of the core. Engineered hardwood flooring is available in almost any wood species.