Engineered wood flooring consists of a solid wood top layer (varying in thickness from 2-6mm) laid on a plywood base layer, which is itself pressed and dried for two days. This solid wood top layer can be sanded up to 6 times, depending on the thickness of the layer. As a rule of thumb, this top layer can be sanded once for each 1mm of thickness. For example, an engineered wood floor with a 6mm solid wood top layer can be sanded up to 6 times over its lifetime.