Having a level sub floor is a prerequisite for laying a parquet floor or ceramic tiles. Your final finished floor will only be as good as the sub floor under it. Preparing the surface underneath the new floor is just about the most important part of the job [source: Hardwood Installer]. So let's see what you can do to level a wood sub floor before starting on the parquet.
- Remove anything covering the sub floor. This includes all carpets, tiles and old parquet. You will now have exposed the plywood sub floor.
- Check the plywood with a spirit level, and locate the spots where it's not level.
- Remove the plywood from any area where a joist is pushing the board upward. Plane the joist down so that it's level with the other joists. Before you start, make sure there are no nails in the joist. When you have finished, check the joist's level against that of the other joists with a spirit level.
- Remove any plywood boards that are sinking lower than the other boards. An indentation in the joist is probably causing the board to sink. Bring up the level of the joist by inserting wooden shims. Check the level against the other joists with a spirit level.
- Reattach the plywood that you removed after you have leveled all the joists. Your wood sub floor should now be level. You can prepare it to receive the parquet [source: Lowes, Readers Digest].