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 slab floor.
To level concrete floors start by cleaning the floor and filling in any cracks or holes with concrete filler and sealer.
Then go over any particularly high spots with a concrete grinder so they re level with the rest of the floor.
Leveling a concrete floor for tile.
Neglecting to prepare the old surface will prevent the new concrete from adhering correctly resulting in a weak bond between the two layers.
When you re finished spread some concrete leveler primer over the floor and let it dry until it has a tacky.
If you want to install vinyl tile or ceramic tile things get a bit trickier.
It may not be quite level or may have dips in the surface which can make it difficult to walk across the floor or to.
If you plan on leveling a concrete floor you can do so with relative ease by using a leveling compound.
It spreads across uneven slabs filling in low spots as it creates a new level surface.
To resurface an uneven concrete slab begin by laying a long straight 2x4 wooden rail across the concrete slab floor with one end positioned on the high point in the room.
Tiles are relatively durable floor coverings that can last for years when laid on a perfectly flat substrate.
Though concrete floors are durable your floor may develop problems over time.
If a tile floor is laid on a subfloor.
You can level an existing concrete floor with a leveling layer of new concrete but you must prepare the old concrete floor first.
An even concrete slab is very important if you plan to build anything on your slab or lay down any type of outdoor tile.
Placing the compound on top of the existing concrete will allow you to make repairs to the low points that may cause problems.