This is easier than it looks!
Sagging floors can be a real problem both in the effect they have on the value of your home and your everyday life.
Although they are most common in older homes newer homes with wide rooms can also have a slight sag to the floor..
There are many professionals who tackle this kind of problem but this is one you can most likely handle your self. If you find the problem to be more serious you should call a professional.
You will need a long level or straight edge. With some floors you can actually see the dip using no tools..
You will need a helper to tap on the floor at the sag while you are under the house. Just listen for the tap and follow the sound.
Make sure it is well lighted under the house so you will be able to see the problem. When you find the spot you will find a sill or joist is sagging or is not properly supported. Sometimes the problem is just too long a span.
In most cases the problem can be fixed with a four by four by eight and three jacks. If the sag is longer use two four by four by eights. Remember the rule one jack every four feet.
The jacks can be purchased at any of the big home stores around Columbia and a lot of the local hardware stores.
In the illustration the four by four is placed parallel under a sagging sill. In other cases it may have to be placed perpendicular under sagging joists.
The jacks are placed no more than four feet apart and on predug concrete pads with a concrete paver on top. The concrete pads should be no less than twelve inches square by twelve inches deep. You can make them using bags of ready mix concrete.
Once the pads are hard and everything is in place have one person screw the jacks while another watches inside the house. It usually takes just a few turns to correct the problem. The jacks are left in place and the sag is gone.
This same fix can be used to take the bounce out of floors. Just adjust the jacks enough to help support the floors and not lift them off their existing supports.