Sagging and bouncy wood floors

Q: My entire home is hardwood. On the first floor the floors are in poor shape due to all the traffic over the years, but this doesn’t concern me too much. My main concern is that my house is over 100 years old and mostly every floor is sagging and not level.

Is there a way to shore them and re-level them from the cellar before we refinish them?

A: If the floor is sagging, a couple of jack posts placed under the affected joists might lift it. You might want to have a contractor look at it.

Similar Q: My original oak hardwood floors in my 85 yr old home have spots near entrances that appear weak, what can I do?

A: Perhaps you can shore up the floor from below.

Another Similar Q: We live in a house built in 1859 with original wood floors. A few of the floor boards located directly over the furnace are bouncy and have cracked slightly. The joists are accessible in the basement and seem very stable but not entirely level. How should we go about fixing these few boards and supporting them?

A: Perhaps you can screw a supporting board to the sub floor between the joists in that bouncy area.

Follow-up: There is no sub floor, just floor boards and joists.

A: Okay, it doesn’t matter. You can still cut a board to fit from one joist to the next, push this board up tight against the floor above and screw in block under each end into the joists to hold it in place.