Remodel - Floor Sag

tmenting

I need some opinions on a remodel project. Actually this job is my own house so time/money are (relatively) not a large determining factor here. Although my wife may say differently.

Our 1st floor is narrower than our upstairs and that means that the load bearing walls that support the roof rest on the floor joists that are the ceiling for the 1st floor. Their is not a load bearing wall DIRECTLY underneath of either of the bearing walls for the roof. There is one wall approx. in the middle of the first floor so it is not an extremely long span. However one of the spans (about 15 ft was contructed (1894) with 2x6's and this is consideralbe sag on this span as it is considerably longer than on the other side of the bearing wall that is in the 1st floor. Finally I will get to the question...Is it better to jack the the old 2x6 up straight then attach the LVL OR since I can get to the top plates of that the floor rests on to just make sure they LVL is resting on the plates and attach the LVL to the sagging 2x6. Understand that I have the upstairs tore apart and have the flooring off so only the top side of these are exposed. Normally I also jack up a floor to get the sag out first but that is only when the current flooring is staying on.

My theory is that if I jack up the old 2x6 and then attach the LVL the natural tendancy of the 2x6 will be to actually pull on the LVL and will not provide any support upwards but to basically already put a "load" on this new beam.

Whereas if I just tack the LVL on the already bent 2x6, the 2x6 is basically bent as much as will probably ever going to bend and by attaching the LVL to this the 2x6 would have to bend more than it is now in order for the LVL to bend.

I usually jack up all floors straight before ataching any sister joists so this doesn't feel quite right but I have been pondering on it for some time now and beleive my thinking is correct.

ANY INPUT OR QUESTIONS HERE?