If the area is very large use a long straight 2 in 4 in 5 1 cm 10 2 cm board and set your level on top of it.
How to level single floor board.
If an engineer found no structural issues you may be able to level the floor by applying a cement based self leveling floor product such as henry level.
If the level isn t long enough lay a flat board along the floor with a level on top.
Cut a leveling strip a very long triangle from a 2 x 10.
A plywood subfloor will bridge any minor waves in the existing floor and leveling compound would help too.
Floors are rarely perfectly level.
You will have to make sure your joists can handle the addition of considerably more weight from the plywood subfloor and any floor coverings.
Rather than attempt to lift the floor by packing out between the boards and the joist the packing invariably works loose as the floor moves with use it is easier and more cost effective in the long run to remove the floor boards and level the joists by fixing new straight ones to the existing.
Cut first leveling strip.
In this video we show you everything you need to know how to level a floor into a perfect flat and level floor in your bathroom using self leveling floor com.