We bought our 25 year-old home a year ago. It is a two level colonial and is a nice house. The family room has a pretty obnoxious "dip" in the floor. From the basement, it clearly obvious that the joist sags at the end. Inspections (by me and a professional contractor) reveal no damage to the foundation or structure.

The joist is about 27' long and level except for the last 6 feet or so where it bows downward for a few feet then curves back up. There is an obvious gap between the joist and sub-floor. At the start of the curve, it drops to 3/8 then curves up at the end with a 1/8 gap.

As I said, there is no apparent damage at it appears the joist was probably bowed when it was installed.

There is some sort of filler material between several of the joists and sub-floor. The area in question seems to have "lost" its filler, causing the floor to be pressed down onto the joist causing the dip.

The contractor said the best thing to do was to install sister joists. If the structor is sound, why mess with it? Can't the sub-floor be re-leveled by shimming?

Thanks so mauch for taking the time to read this and any advice you can give will be appreciated.

-Carl