I have a 12 foot floor span with a pier in the middle. Due to obstructions I can not sister the joists on one side. I would like to sister one joist on one side to the pier (6 foot span) and for the remaining 6 feet sister on the other side. Is there a problem with this?
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Yes; that's a problem.
Bending stress is maxium at center span of a simply spanned joist. You're not increasing the bending capacity of existing joists at all by sistering as you propose. For maxium effectiveness, keep the sistering member the same length as existing joists and continuous on one side. Fasten both members together sufficiently with nails or strucutral screws to achieve good composite action.
That was a very nice and kind reply ..
to this post and a clean explanation as to why his plan will not work. Good job.
joist span
If I understand this situation correctly, your existing joists are spanning 12' while bearing on a pier at midspan (6').
You would like to double the joists by adding a 6' joist on one side of the existing joist and on the other half of the span by adding the joist on the opposite side of the existing joist.
If, and only if, each of the sister joists are bearing on the center pier and on the outer bearing points, then yes you could fasten one sister joist on each side of the existing joist, BUT the original (12') and the sister joists(one on each side of the original 12' joist) must BOTH be bearing on the center pier AND the outer bearing points. If that is not the case, it will not work .
It will work only if the situation is as I described, since then you are effectively doubling the joists only over a 6' span. If the 12' joist and the 6' joist do not rest on the center pier it will not work!
Good Luck
Geoff
Do note that Opie has not been heard from since he originally posted, and has not responded to a question specifically asking if the joists bears on the center pier.