I am renovating the kitchen in my 100+ year old American Four Square home. I was unfortunately not able to salvage the original longleaf pine flooring, so it has all been pulled up. I'm left with original rough sawn 2x8 joists (spanning about 13'). The problem I am facing is that none of the joists are in the same plane, even at the ends where they are sitting on the foundation (one end) and a support wall (other end).
Luckily, there is a cinder block wall near the middle of the span running perpendicular to the joists. The most obvious thing to do is shim under that to get the middle sag out of each joist. But since none of the joists are in the same plane at the ends, this job isn't as simple as that. I'm not quite sure how to tackle this problem. Can anyone point me in the right direction?
Here are some pics of the room. Notice that there is one point in the foundation wall where the joists are resting on a wood header and they notched the end of a few joists halfway up. If you have any idea how to address that, that would be great, too.
EDIT - Finished Job
Thanks for all the advise. I decided to go with the shimming approach, which was a bit tricky because the joist are quite wavy (up and down). I created custom shims by scribing a pattern on to a level 2x4 and cutting on the scribe line with a jig saw.
If I would have had fewer mechanicals in the joist bay, sistering would have probably been faster and easier. Ripping 14' with a jig saw is time consuming and I still had to use additional shims when my scribe wasn't accurate enough. I used Advantech subfloor adhesive to set the shims in place, then used a variety of screws to secure each shim. In some places I needed to use 3" screws because my shim was about 1.5" tall!
If you haven't used Advantech subfloor or adhesive before, I highly recommend it.
Sistering probably would have been necessary if I wasn't lucky enough to have a block wall mid way under the joists to act as a girder. The original joists would have needed the extra strength from a glued and screwed sister without the block wall.
Here is what it looks like with the shims installed: