Engineered wood floors are generally 2,3, or 5 thin sheets of wood that are laminated together to form one plank. These floors will range from 1/4" to 9/16" in thickness, and from 2 1/4" to 7" in width. The lengths will be random and range from 12" - 60" in length. The top finish layer can be cut from a variety of domestic or exotic hardwood species.
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 than a 3/4" solid wood floor. This means you can install these floors over concrete slabs in basements, as well as anywhere else in the home.
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. So if moisture is a concern then you should choose an engineered type floor versus a solid strip floor.
Because engineered wood floors are made up of several layers of wood that are all glued together it's 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.
Most engineered floors can be nailed down, stapled down, glued down, or floated over a wide variety of subfloors, including some types of existing flooring. You can also buy engineered floors in varying widths. They generally come in 2 1/4", 3", 5", and 7" widths and widths can be mixed, such as 3-5-7 inch planks installed side by side. By varying the board widths you can change the total appearance of the floor.
2 1/4" width
traditional linear look
3",5", & 7" widths
more patterned look