Remove any paint, wax, sealants, adhesives, and debris. Be sure the subfloor is completely dry before beginning to install the parquet flooring. Use a belt sander to sand any high areas and/or fill any sunken areas with cement leveling compound. The subfloor needs to be smooth and level to ensure the overlaid parquet floor is level.

Summary:
Clean the subfloor. Level the subfloor. Replace any damaged areas in the subfloor. Tighten any loose areas of the subfloor.