For proper installation, your base floor needs to be flat, clean, and ready to accept your choice flooring. Most floor coverings can usually be installed successfully right over old floor coverings, such as sheet vinyl, provided the surface is flat and smooth. A simple underlayment of foam sheeting is usually sufficient as a base for laminate planks. If the floor surface has damage or unevenness, though, you may need to remove it and lay down a rigid underlay of thin plywood before laying the foam sheets and installing the laminate flooring.