Sistering joist questions
I am planning to sister a joist that has sagged over time and have the following questions:
(A) As shown in the diagram, the original (old) joist (and floor) are bowed by about Â¾" in the center. So how can I fit the sister underneath, assuming the new sister is a straight 2x8 ?
One way, I thought, would be to notch the ends of the sister (where the sister will rest on the sill) to compensate for the bow in the original joist. If so, the sister will end up not resting completely on the sill (there will be a small gap between sill and sister as it will be impossible to get the notch depth just right).
Another alternative, I thought, would be to use a floor jack to put pressure on the center of the old joist until it crowns and then slip the sister underneath. But IÂm skeptical I can completely undo a Â¾" 50 year old joist bow that way.
Is there an alternative?
(B) Given the fact that joists are 16" OC. seems to me, that it will be inevitable to cut the sister joist a little shorter than the old joist in order to get the sister into the joist bay. Now again the sister does not fully sit on the sill. Is there another way?
(C) I will attach the sister to the original with bolts or lag screws (one better that the other?). Should I also glue them together (thatÂs what I saw on a Bob Villa YouTube video)? If so, what should I use? Wood glue or some sort of construction adhesive such as "Liquid Nails" or "PL 400"?
Finally, am I making a big deal out of (A) and (B), fretting about the fact that the sister will not fully sit on sill and that it will be a little shorter than the old joist when, perhaps, the objective here is just to reinforce mainly the center of the original sagged joist?
NOTE: Joists are 2x8s on 12Â span. Sill is 6", foundation wall is 16".