Slip shims under the low end of the 2x4 rail until it s perfectly level then use a scribing tool to transfer the unevenness of the floor onto the rail.
How to level a concrete floor with mortar.
Grinding and repairing a concrete floor can create concrete dust so be safe and wear a respirator.
If you want to install vinyl tile or ceramic tile things get a bit trickier.
For a successful installation the concrete floor beneath the tile needs to be.
If you plan on leveling a concrete floor you can do so with relative ease by using a leveling compound.
Whether you want to refinish an uneven basement floor or replace or add new flooring on top of an existing concrete floor somewhere in your home you most likely will need to level the concrete floor.
A dust mask will not give you enough protection.
Keep checking the floor with a level as you grind the concrete.
Over time concrete floors can settle unevenly or become uneven due to cracking and moisture.
Filling in gaps cracks and crevices as well as leveling uneven concrete will bring up the aesthetic and shore up the structure of the flooring.
Leveling a concrete floor for tile.
It spreads across uneven slabs filling in low spots as it creates a new level surface.
An uneven concrete floor can be unsightly as well as unsafe.