Ball
When in doubt about floor flatness, you can use a simple metal or plaster bead. It must be put on the floor, which visually is in doubt, and to follow his movements. If the ball will remain in place – the plot is perfectly flat. In the same case, if the ball begins rapidly rolling into a corner or to move in different directions – the floor needs leveling.
That way you can use even when buying an apartment to make sure that the installation of flooring does not require much additional work.
Rake
To check floor flatness, you can use straight rail (it is also called "rule"). It should be long enough to identify minor irregularities, but the overall slope surface.
The rail is installed on the caller suspected the plot and marked with labels on the wall. It is better to set the level. The voids formed between the rod and the floor surface is measured by tape and marked by marks on the adjoining wall.
Special devices
A more accurate method – hydraulic or laser level. These special devices allow to detect all the irregularities of the floor. Moreover, the laser level is more accurate.
Hydrolevel any is a hose with two clear water tanks at the ends. The water level allows to determine the slope of the surface in contact with the floor. In turn, laser level automatiseret this process, allowing you to install it on any part of the floor and mark the laser beam point on the wall that you only need to put down the pencil construction. Several checkpoints in different areas of the floor allow you to define the problem of plane that require additional work.