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Discovered Living Room floor has no cross bracing - bouncy

Discovered Living Room floor has no cross bracing - bouncy

Old 03-21-23, 12:48 PM
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Discovered Living Room floor has no cross bracing - bouncy

While prepping/leveling for new LVP flooring, I had to remove a piece of OSB subfloor to plane down a joist that was about 1/2 inch too high in the middle. While in crawl space I noticed the joists run a 13 ft span but have no bracing/blocking. So some are now twisted a bit and that likely allowed the high joist to twist upward more easily. House is 25 yrs old. And of course floor could be firmer overall.

What is the best way to reinforce the floor now? Probably add Blocking - but end to end or offset? Do the new metal cross braces work? Can you install them on existing floor? I am sure some of the twists in joists may make cutting blocking to size an issue with fitment? Any secret techniques for that like special clamps, etc to pull joists more true when attaching blocking? Also, do sister joists have to be full end to end in length, same as original, same width (2 x 10?)?

Old 03-21-23, 12:53 PM
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The answer to your question is similar to what's discussed in this recent thread.

Bouncy floor support advice please.

Start with tight fitting wood blocking where the joists are still square and plumb, and you should be able to force any that have twisted back in line. It's just a matter of finding the measurement at the top, cutting the block square, and driving it in. Alternating pattern is fine, as shown in the replies in that thread.

Sistered joists should really span from bearing wall to bearing wall. Depends what you are trying to accomplish and what's possible due to constraints.
Old 03-21-23, 03:02 PM
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No, you can't use the metal diagonal braces. One end gets attached over the top of the stud so they really can't be installed after the subflooring is down.

The method XSleeper mentioned works with the blocking. The top of the joist are held in position by the sheeting nailed in the top but the bottom is relatively free to move. When doing this I like to cut one or two blocks at a time, install them, then adjust the blocking size for the next batch. This way slight errors in your measuring or cutting don't accumulate.

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