Hi I have a 7 year old house all 16" tgi joists 2' on center with 2 layers of 3/4 t/g plywood over them. It was supposedly build extra heavy for tile.

The great room is 24x24 with the tji's spanning the whole floor at about 23'In the past year it has become bouncy, noticed mostly when the two dogs run across it. But the lamp shades move and it's freaking me out.

It's a full unfinished basement underneath. There is no x or other bracing on the TGI's. I measured the center of the floor and it's about 1 1/2" lower than the edges.

Is there anyway to stengthen the floor or raise it back up? Can more joists be installed with the wiring already going through them? I may be able to support it about 1/3 of the way in with a wall when the basement is finished. Should some type of bracing be installed on the joists?

Please let me know so I can find a contractor to help.

Thanks for any help.
Dana Kelly