Self -alignment is one of the mandatory procedures for its repair and subsequent laying of bulk or parquet flooring. The basis in this case is supposed to be concrete.
To begin with, if the floor is not too crooked, you can try to process it with the most ordinary grinder. Only take the paper on it with a large faction-it is better if it is the 50th fraction. 120 fraction is designed for wood.
And the concrete floor you will not be able to damage the 50th faction. Grinding concrete floors minimizes porosity.
If the situation is greatly launched, and the floor is frankly crooked, then only reloading the floor with concrete will help you. But the thickness of the layer of new concrete should not be large, since your ultimate goal is not the creation of a concrete floor as such, but the repair and preparation for laying the material.
Very demanding on the floor level of bulk floors. If they are put on an uneven floor, then bulk floors, even the highest quality, will constantly swell. To prevent this from happening, it is better to completely reload the floor and in addition, after the concrete layer dries, to align with an additional grinder.
Also try to clean the floor thoroughly (it is better to vacuum it) before laying bulk floors. Outclocking will not help, you need a perfectly smooth, clean and even floor. It will serve as the basis for the bulk floor for many years, so there should not be any flaws on it.