I am in the process of purchasing a 30 year old home that has a spongy upper floor, when you jump around in the span of the floor where the metal beams are not the floor reflux or bounces up and down. How extensive is my corrective action? Is there a weight capacity this type of floor will support? and How safe is the upper floor?
This is where your Home Inspector comes in. Depending on the span distance, HOPEFULLY, the current or previous owner didn’t remove a Lolly Column, or the like, where it is suppose to hold up the span! The floor may or may not be safe. The Inspector needs to look for ‘signs’ of a weight bearing wall (down below) and the possible placement of a Column.
At the same time, your situation may be just age. Your joists may be sagging for a variety of reasons. Have the home inspected since we can’t see it from here. Your ‘problem’ may simply require re-screwing the sub-floor, adding shims, adding a Column, replacing a ‘bad joist’, among others.
Other Follow-uppers may have more to add. My best to ya and hope this helps.