My husband and I are remodeling a 1900's foursqare. We have taken out all of the plaster and lathe in the downstairs rooms as it was in bad condition. Prior to this I had noticed that the upstairs floors on one side of the house had a significant slope of 1"-2". When we removed everything on the walls and ceiling we were able to see that the loadbearing wall has no "beam" but two 2x4" stacked on top of eachother which have been cut in half to allow a vent to go through that is no longer in use. The floor joists that are resting on this are 2x6" and sag in the middle, some of them appear to be almost falling off the 2x4"s where they have been notched. The load bearing wall in that room is also not adaquitely supported and we were planning on fixing that by doubling up the 2x4" studs and creating a box beam with plywood over the doorway. I would like to know if anyone has had any experience dealing with this type of problem and how it was fixed. I would like to fix the support and sag issue as much as possible because when you walk upstairs everything shakes and things fall off of shelves. This issue is only on one side of the house, I'm not sure why that is we have been told that half of the house was an addition and it is possible that this is the older origional side as far as I can tell. If possible I would like to deal with this while we have everything open if it is a safety issue rather than wait. I have attached a picture of the wall, the room behind it is having the sagging issue.