Floor joist problem

[wecker20]

Newbie here and I'm learning as I go. I'm in the ongoing process of remodeling and fixing up our 100+ Centenial Farm house. I removed the plaster and lath from the two rooms I want to re-do and found some sorry building techniques. Working on the first story now and need to fix the saggy, bouncy 2nd story floors. Floor joists are 2x6, some true, some not and run a 17' span, 16"oc! Here's another problem, they are spliced and sistered. Each 2x6 is 12ft in lenght, spliced/sistered into another 12ft 2x6. What is the best way to correct this? I was looking into 9 1/2" I Joists but not really sure how I would incorporate these into the existing framing. Looks like the min. on a 17' span is 2x12's 12" o.c.? Could I sister 2x8, 10, or 12's onto the old joists and still have a safe, sturdy, straight floor? I want to do it right now and not have to worry about it. No load bearing walls above this floor and I cannot rip up the subfloor.

[Don_P]

2x10 Select structural yellow pine or doug fir on 16" ctrs or 2x12 #2's of spf or better on 16's will do it. So sistering will work, the ends are a problem though. Although the bending moment is low there the notching provisions limit you to 1/4 depth. You could nail a ledger across the studs on the load bearing walls under the new joists and call it a crown detail, not great. you could then sister new studs to the old projecting into the room 1-1/2" to support that ledger and the new joists, lotsa wood and probably messes with window and door jambs.

If there is room a girder across the room breaking the span in half would work, you need to support its end posts to footings below.

The I joists will work with the least depth most likely.

There's several ways but its almost impossible to brainstorm it online.

They don't build them like they used to, thank goodness!

[wecker20]

thanks for the reply. I've been doing a lot of brainstorming on how to go about fixing it and the best I can come up with is 2x10's sistered with the ledger across the studs. There are rooms added on to the outside of these rooms so I only have to deal with two doors with the new 1 1/2" (Actually will only be 1/2" because of removing the 1" sheathing. If I can live with the lower ceiling, I might just have to go with the 2x12's. I'm 6'4" so 2" lower is a lot.