Hardwood flooring are typically 3/4" or 19mm thick, although some do come in 3/8" (10mm) or 5/16" (8mm) thicknesses. Typically the wearing thickness, i.e., the thickness that can be sanded over the lifetime of the floor, above the tongue-and-groove portion, is approximately 7/32" approaching 1/4". This type of wood flooring can be installed with a nail-down installation method over wood subfloors. This type of hardwood is also very susceptible to the effects of moisture and temperature, because hardwoods expand and contract with moisture and temperature changes in the atmosphere.
Engineered hardwood flooring is composed of layers of hardwood veneer, which ranges in thickness from 3/8" or 8mm up to 9/16" or 14mm thick. The wood veneer can range in thickness depending on the manufacturer, as will the top wearing thickness. In order to create an engineered hardwood, these veneer layers are stacked one on top of the other with the grain of adjacent layers oriented perpendicular to one other. Once the desired thickness is achieved, the boards are then cut into the correct board width. From there, the boards are then manufactured to have a tongue or groove on the edges. The final step is to add stain if necessary, and add a finish.