I have a floor joist that has a crack down the center of the board (about 8 feet). I recently noticed it after hearing my floor start to creak above it. There doesn’t appear to be any floor sagging yet but I wanted to get ahead of it since this joist is down the center of my house. What do you recommend I do with a crack this long? I was thinking about sistering a joist but not sure I could get the same length wood in.

Video of damage

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  • Size of joist and the open span it covers? Usually an horizontal crack in a joist is common.
    – crip659
    Commented Apr 18 at 15:46
  • Were you able to view the video I uploaded?
    – Mike Pak
    Commented Apr 18 at 16:25
  • 1
    @isherwood ,I thoroughly agree with answer you linked to. From the video, I seen the cracks were not all the way through, all "checks". no concern for the integrity at all
    – Jack
    Commented Apr 18 at 21:02
  • 1
    @Jack - This is very subjective to where you are but "checks" are not just glossed over by any inspectors in my area. In fact all structural engineers I have worked with have pointedly made us repair them - ALL. Isherwood's answer would be considered wrong and dangerous, if you ask any inspectors that have been out to my houses. Checks are weak points were shifting could easily move the checks into something that is useless structurally - especially with horizonal load. I usually don't see much variance with answers on this site but this does not ring true where I am .
    – DMoore
    Commented Apr 24 at 21:20

2 Answers 2


If an inspector in my area saw this (or if I saw it) they would ask me to reinforce with Simpson strong ties or something to the like plus a sistered 2x#. Adding the tie plus 2x# would literally take 10 minutes.


Start with inject glue (construction adhesive), jack to close crack on the glue, and apply plywood to both sides (if accessible - your video shows a quick shot of what seems to be quite a small gap on the backside - unclear how it's actually laid out) with glue and nails, or structural screws. The fastener needs shear strength. Attach the sister, if any, so the plywood on one side of the original is sandwiched between the original and the sister. Plywood resists splitting very well by its nature.

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