Level a subfloor with sagging joist for hardwood floor

malicio

So here is my dilemma . Recently moved in, removed the carpet from a floor in the den, removed the parquetry underneath to be able to put in hardwood. Managed to level parts of the floor from beneath due to missing joist hangers. Also bought some self levelling underlayment from some tricky areas that not possible to fix from beneath. However found out that towards the wall there is a little dip at least 1/4". Found out that below the wall there is a 15' x 9" joist sitting on a major beam and sill plate, however there is only one joist beneath this wall! And there is another wall on the second floor in the same place.

The joist seems to have sagged slightly but with no damage to sill plate or beam.

My options:
1. Lift the joist and install a sister joist (not so easy as I have to remove part of the ceiling beneath and some electric wires (hopefully no pipes)
2. Suck it up and just put some self levelling underlayment (problem with this though is it is almost the entire wall length (14 ft) therefore the additional plywood have to put cannot be screwed down close to that part (unless I block off pre-designated areas with some parquety to avoid underlayment going there and then screw the ply there and glue ofcourse).

How much of a sag, well the pictures will tell.

Thanks for all your feedback!

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gregzoll

One way to do it, would be to get the floor lifted from below, and shim down there, but if any doors where changed out after the house settled, would have to have frames adjusted. Other way is to get some 2x4 ripped down at the angle that the floor dips, and then use Carpenter's glue, or glue with wood glue and then put in some finishing nails to hold, then would be able to lay the floor over the top.

My house has sunk in one corner, and for some reason when we moved in, there was a lolly column in the middle of the living room, but checked out not needed, so we removed it. Old houses are a PITA, but if fixed up correctly, they will last a very long time. Longer than the sub-grade homes that are built now days.

malicio

Yep, tell me about it. My house is from 72 - moved in a few months ago and the major reno has never stopped.
I think for this situation I will cut the floor out since it is such a small piece, put the 2x4 with glue. The problem with the shims is that lifting the floor will probably crack the tile on the other side of the wall, and it won't be easy to lift with the wall above the joist

gregzoll

Or, just put down some Luan to bring that section back up even. I could beat you on age, my house was built around 1939, about as old as my dad. Old houses keep you as busy as young kids and Toddlers.

KCB

your plan "1" is the best should have been doubles anyway on an end wall with an upstairs .Fix it now and be done with it you wont regret it in the long run