Joists are slightly different width


Old 02-09-14, 11:19 AM
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Join Date: Jan 2014
Location: USA
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Joists are slightly different width

We are preparing to lay hardwood floor in our kitchen and I discovered a hump in the subfloor. The high spot is 2 or 3 inches wide and runs about a foot or two. I went to the crawlspace to see if I could determine what was causing this.

The hump occurs just past the support beam for the load bearing wall. The kitchen and living room are on opposite sides of this load bearing wall and have separate 2x8 joists. The joists for each room go about two feet past the support beam and are nailed together. I can see that where the hump occurs in the kitchen, the subfloor is making contact with the living room joist but not the kitchen joist. They appear flush on the bottom, but the living room joist is about 1/4" wider. Consequently, the subfloor is fastened all along the kitchen joist until it gets to the last 18 inches of the room, where it is fastened to the joist in the living room.

The two joists are nailed together in this spot, but have pulled apart up where the subfloor is making contact and I have contact with the beam on both joists. I was thinking about trying a carriage bolt through the two joists where they are pulled apart about 1/2 inch. I'm less than enthusiastic that this will fix the problem or even make the rise in the floor more gradual. Any ideas on how to fix this spot?
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Old 02-09-14, 12:39 PM
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Join Date: Dec 2004
Location: USA
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You have 2 options. 1). Cut back the subfloor on the living room side so that you can surface plane the tops of the joists so that they match. <- probably more work than it's worth... or 2). shim up the joists on the kitchen side and lay the new subfloor to match the old, so that the "hump" is less noticeable.

There should have been solid blocking installed between the joists above the load bearing wall so that the joists could not tip to the side. That's what allowed the joists to separate and cause the gap where they overlap each other.
Old 02-09-14, 01:26 PM
Join Date: Oct 2008
Location: New England
Posts: 9,991
Not a pro at this but I have a similar situation that I have pondered for years. New floors going in soon so I have to stop procrastinating . Access and space are important issues. My solution will be to cut a notch horizontally into the joists in the area where they need to come down. I'll be generous to each side to give the wood plenty of length to bent. Once notched, say 4' on the one that overhangs the support, I will use bolts or torque screws to pull the beam together. I should be able to shrink my tall 2x10 by at least 1/2". I'm not worried about strength as I can always sister the joists if needed.

The primary concern is, will the floor come down with the beam? With a new floor covering going in I will be able to screw it down from the top and hopefully eliminate the hump. If I cut out too much, then I will shim as X stated.

For making the cut, a hole at the start and a saber saw should work, albeit slow.


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