You may find this task easier if you hold the string off the sagging floor joists by attaching blocks of the same thickness at opposite sides of the basement.
How to level a floor foundation.
This video is for more experienced builders or for those who want an inside view of foundations and subfloors.
This video goes over some basic foundation and.
A pier and beam house foundation essentially elevates the house above the ground to provide a level platform based on specifically positioned footings.
If you suspect that you re working with an off level foundation you can get it ready for installation quickly by using a floor leveling compound.
With a taut string water or laser level make a straight line from one side of the foundation to the other.
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.
Level floors are critical for reducing gaps between the flooring material and substrate and preventing sagging and other structural complications.
Nail them to the underside of the joists as near the foundation as you can.
Instead it may be an issue with joists and beams below your floor that require shoring up.
For instance you may have a dining room floor that end to end is level but between those two points are various sags and dips.