Uneven Subfloor
#5
  
I have a 16' x 12' room which is built upon an area of the house which is over the meeting of 3 different additions.  It's a one story house over a crawlspace.  There's no damage to the joists, but the joists from the different additions don't meet up perfectly to create a flat subfloor.  None of the joists are are longer than 8' and they are 2 x 8's.  The subfloor is a hodgepodge of tongue and groove planks and plywood.  I'm going to rip all of that out.  Once down to the joists can I just sister new boards to the joists to create a level surface for my subfloor?  If so, do they need to rest on the foundation or can they just be attached to the existing joists; do they also need to be 2 x 8s?  I appreciate any input. 

Ken
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#6
  Re: Uneven Subfloor by APZ (I have a 16' x 12' r...)
Just sister 2x4s or 2x6s to the floor joists. Construction adhesive and pop it on with a nail gun or construction screws.
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#7
  Re: Uneven Subfloor by APZ (I have a 16' x 12' r...)
(11-03-2019, 10:53 AM)APZ Wrote: I have a 16' x 12' room which is built upon an area of the house which is over the meeting of 3 different additions.  It's a one story house over a crawlspace.  There's no damage to the joists, but the joists from the different additions don't meet up perfectly to create a flat subfloor.  None of the joists are are longer than 8' and they are 2 x 8's.  The subfloor is a hodgepodge of tongue and groove planks and plywood.  I'm going to rip all of that out.  Once down to the joists can I just sister new boards to the joists to create a level surface for my subfloor?  If so, do they need to rest on the foundation or can they just be attached to the existing joists; do they also need to be 2 x 8s?  I appreciate any input. 

Ken

When you get down to the joists you may find that shimming a couple of joists will do the trick. If not, do like Robert suggests and add a 2x6 along each joist. Another way that I have seen but not done myself is to pour self leveling gypsum onto the existing floor. I have worked on these floors and had to lay protection down so my shoes did not scuff up the soft gypsum. I imagine carpet is laid over this. Probably the least expensive way but not necessarily the best. I was told recently that new gypsum floor levelers have a hydraulic cement mixed in and are much better than the product I have seen in the past.
mike
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#8
  Re: Uneven Subfloor by APZ (I have a 16' x 12' r...)
Thanks guys.  I already tried self leveling and that didn't work out so well.  I just spent the weekend undoing that mistake and my body didn't appreciate it.  (And I still need to undo the hallway.)   Laugh   I'm better with wood than concrete.  Plug here for the Harbor Freight Bauer rotary hammer. 

2x6 attached to the joists is the current plan.
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